Content      ..     14      15      16      17     ..

ISO 32000-1 Document management — Portable document format — Part 1: PDF 1.7 - page 16

Often an illustration is logically part of, or at least attached to, a paragraph or other element of a document. Any

such containment or attachment shall be represented through the use of the Figure structure type. The Figure

element indicates the point of attachment, and its Placement attribute describes the nature of the attachment.

An illustration element without a Placement attribute shall be treated as an ILSE and laid out inline.

For accessibility to users with disabilities and other text extraction purposes, an illustration element should

have an Alt entry or an ActualText entry (or both) in its structure element dictionary (see 14.9.3, “Alternate

Descriptions,” and 14.9.4, “Replacement Text”). Alt is a description of the illustration, whereas ActualText

gives the exact text equivalent of a graphical illustration that has the appearance of text.

14.8.5

Standard Structure Attributes

14.8.5.1

General

In addition to the standard structure types, Tagged PDF defines standard layout and styling attributes for

structure elements of those types. These attributes enable predictable formatting to be applied during

operations such as reflow and export of PDF content to other document formats.

As discussed in 14.7.5, “Structure Attributes,” attributes shall be defined in attribute objects, which are

dictionaries or streams attached to a structure element in either of two ways:

•

The A entry in the structure element dictionary identifies an attribute object or an array of such objects.

•

The C entry in the structure element dictionary gives the name of an attribute class or an array of such

names. The class name is in turn looked up in the class map, a dictionary identified by the ClassMap entry

in the structure tree root, yielding an attribute object or array of objects corresponding to the class.

In addition to the standard structure attributes described in 14.8.5.2, “Standard Attribute Owners,” there are

several other optional entries—Lang, Alt, ActualText, and E—that are described in 14.9, “Accessibility

Support,” but are useful to other PDF consumers as well. They appear in the following places in a PDF file

(rather than in attribute dictionaries):

•

As entries in the structure element dictionary (see Table 323)

•

As entries in property lists attached to marked-content sequences with a Span tag (see 14.6, “Marked

Content”)

The Example in 14.7.6, “Example of Logical Structure,” illustrates the use of standard structure attributes.

14.8.5.2

Standard Attribute Owners

Each attribute object has an owner, specified by the object’s O entry, which determines the interpretation of the

attributes defined in the object’s dictionary. Multiple owners may define like-named attributes with different

value types or interpretations. Tagged PDF defines a set of standard attribute owners, shown in Table 341.

Table 341 - Standard attribute owners

Owner

Description

Layout

Attributes governing the layout of content

List

Attributes governing the numbering of lists

PrintField

(PDF 1.7) Attributes governing Form structure elements for

non-interactive form fields

Table

Attributes governing the organization of cells in tables

593

Table 341 - Standard attribute owners (continued)

Owner

Description

XML-1.00

Additional attributes governing translation to XML, version

1.00

HTML-3.20

Additional attributes governing translation to HTML, version

3.20

HTML-4.01

Additional attributes governing translation to HTML, version

4.01

OEB-1.00

Additional attributes governing translation to OEB, version

1.0

RTF-1.05

Additional attributes governing translation to Microsoft Rich

Text Format, version 1.05

CSS-1.00

Additional attributes governing translation to a format using

CSS, version 1.00

CSS-2.00

Additional attributes governing translation to a format using

CSS, version 2.00

An attribute object owned by a specific export format, such as XML-1.00, shall be applied only when exporting

PDF content to that format. Such format-specific attributes shall override any corresponding attributes owned

by Layout, List, PrintField, or Table. There may also be additional format-specific attributes; the set of

possible attributes is open-ended and is not explicitly specified or limited by Tagged PDF.

14.8.5.3

Attribute Values and Inheritance

Some attributes are defined as inheritable. Inheritable attributes propagate down the structure tree; that is, an

attribute that is specified for an element shall apply to all the descendants of the element in the structure tree

unless a descendent element specifies an explicit value for the attribute.

NOTE 1

The description of each of the standard attributes in this sub-clause specifies whether their values are

inheritable.

An inheritable attribute may be specified for an element for the purpose of propagating its value to child

elements, even if the attribute is not meaningful for the parent element. Non-inheritable attributes may be

specified only for elements on which they would be meaningful.

The following list shows the priority for determining attribute values. A conforming reader determines an

attribute’s value to be the first item in the following list that applies:

a) The value of the attribute specified in the element’s A entry, owned by one of the export formats (such as

XML, HTML-3.20, HTML-4.01, OEB-1.0, CSS-1.00, CSS-2.0, and RTF), if present, and if outputting to that

format

b) The value of the attribute specified in the element’s A entry, owned by Layout, PrintField, Table or List, if

present

c) The value of the attribute specified in a class map associated with the element’s C entry, if there is one

d) The resolved value of the parent structure element, if the attribute is inheritable

e) The default value for the attribute, if there is one

NOTE 2

The attributes Lang, Alt, ActualText, and E do not appear in attribute dictionaries. The rules governing their

application are discussed in 14.9, “Accessibility Support.”

594

There is no semantic distinction between attributes that are specified explicitly and ones that are inherited.

Logically, the structure tree has attributes fully bound to each element, even though some may be inherited

from an ancestor element. This is consistent with the behaviour of properties (such as font characteristics) that

are not specified by structure attributes but shall be derived from the content.

14.8.5.4

Layout Attributes

14.8.5.4.1

General

Layout attributes specify parameters of the layout process used to produce the appearance described by a

document’s PDF content. Attributes in this category shall be defined in attribute objects whose O (owner) entry

has the value Layout (or is one of the format-specific owner names listed in Table 341).

NOTE

The intent is that these parameters can be used to reflow the content or export it to some other document

format with at least basic styling preserved.

Table 342 summarizes the standard layout attributes and the structure elements to which they apply. The

following sub-clauses describe the meaning and usage of these attributes.

As described in 14.8.5.3, “Attribute Values and Inheritance,” an inheritable attribute may be specified for any

element to propagate it to descendants, regardless of whether it is meaningful for that element.

Table 342 - Standard layout attributes

Structure Elements

Attributes

Inheritable

Any structure element

Placement

No

WritingMode

Yes

No

BackgroundColor

Yes

BorderColor

No

BorderStyle

Yes

BorderThickness

Yes

No

Color

Padding

Any BLSE

SpaceBefore

No

ILSEs with Placement other

SpaceAfter

No

than Inline

StartIndent

Yes

EndIndent

Yes

BLSEs containing text

TextIndent

Yes

TextAlign

Yes

Illustration elements

(Figure,

BBox

No

Formula, Form)

Width

No

Table

Height

No

TH (Table header)

Width

No

TD (Table data)

Height

No

BlockAlign

Yes

InlineAlign

Yes

TBorderStyle

Yes

TPadding

Yes

595

Table 342 - Standard layout attributes (continued)

Structure Elements

Attributes

Inheritable

Any ILSE

LineHeight

Yes

BLSEs containing ILSEs or

BaselineShift

No

containing direct or nested

TextDecorationType

No

content items

TextDecorationColor

Yes

TextDecorationThickness

Yes

Grouping elements Art, Sect,

ColumnCount

No

and Div

ColumnWidths

No

ColumnGap

No

Vertical text

GlyphOrientationVertical

Yes

Ruby text

RubyAlign

Yes

RubyPosition

Yes

14.8.5.4.2

General Layout Attributes

The layout attributes described in Table 343 may apply to structure elements of any of the standard types at the

block level (BLSEs) or the inline level (ILSEs).

596

Table 343 - Standard layout attributes common to all standard structure types

Key

Type

Value

Placement

name

(Optional; not inheritable) The positioning of the element with respect

to the enclosing reference area and other content:

Block Stacked in the block-progression direction within an

enclosing reference area or parent BLSE.

Inline

Packed in the inline-progression direction within an enclosing

BLSE.

Before Placed so that the before edge of the element’s allocation

rectangle

(see

“Content and Allocation Rectangles” in

14.8.5.4,

“Layout Attributes”) coincides with that of the

nearest enclosing reference area. The element may float, if

necessary, to achieve the specified placement. The element

shall be treated as a block occupying the full extent of the

enclosing reference area in the inline direction. Other content

shall be stacked so as to begin at the after edge of the

element’s allocation rectangle.

Start

Placed so that the start edge of the element’s allocation

rectangle

(see

“Content and Allocation Rectangles” in

14.8.5.4,

“Layout Attributes”) coincides with that of the

nearest enclosing reference area. The element may float, if

necessary, to achieve the specified placement. Other content

that would intrude into the element’s allocation rectangle shall

be laid out as a runaround.

End

Placed so that the end edge of the element’s allocation

rectangle

(see

“Content and Allocation Rectangles” in

14.8.5.4,

“Layout Attributes”) coincides with that of the

nearest enclosing reference area. The element may float, if

necessary, to achieve the specified placement. Other content

that would intrude into the element’s allocation rectangle shall

be laid out as a runaround.

When applied to an ILSE, any value except Inline shall cause the

element to be treated as a BLSE instead. Default value: Inline.

Elements with Placement values of Before, Start, or End shall be

removed from the normal stacking or packing process and allowed to

float to the specified edge of the enclosing reference area or parent

BLSE. Multiple such floating elements may be positioned adjacent to

one another against the specified edge of the reference area or placed

serially against the edge, in the order encountered. Complex cases

such as floating elements that interfere with each other or do not fit on

the same page may be handled differently by different conforming

readers. Tagged PDF merely identifies the elements as floating and

indicates their desired placement.

597

Table 343 - Standard layout attributes common to all standard structure types (continued)

Key

Type

Value

WritingMode

name

(Optional; inheritable) The directions of layout progression for packing

of ILSEs

(inline progression) and stacking of BLSEs

(block

progression):

LrTb Inline progression from left to right; block progression from top

to bottom. This is the typical writing mode for Western writing

systems.

RlTb Inline progression from right to left; block progression from top

to bottom. This is the typical writing mode for Arabic and

Hebrew writing systems.

TbRl Inline progression from top to bottom; block progression from

right to left. This is the typical writing mode for Chinese and

Japanese writing systems.

The specified layout directions shall apply to the given structure

element and all of its descendants to any level of nesting. Default

value: LrTb.

For elements that produce multiple columns, the writing mode defines

the direction of column progression within the reference area: the

inline direction determines the stacking direction for columns and the

default flow order of text from column to column. For tables, the writing

mode controls the layout of rows and columns: table rows (structure

type TR) shall be stacked in the block direction, cells within a row

(structure type TD) in the inline direction.

The inline-progression direction specified by the writing mode is

subject to local override within the text being laid out, as described in

Unicode Standard Annex #9, The Bidirectional Algorithm, available

from the Unicode Consortium (see the Bibliography).

BackgroundColor

array

(Optional; not inheritable; PDF 1.5) The colour to be used to fill the

background of a table cell or any element’s content rectangle (possibly

adjusted by the Padding attribute). The value shall be an array of

three numbers in the range 0.0 to 1.0, representing the red, green, and

blue values, respectively, of an RGB colour space. If this attribute is

not specified, the element shall be treated as if it were transparent.

BorderColor

array

(Optional; inheritable; PDF 1.5) The colour of the border drawn on the

edges of a table cell or any element’s content rectangle (possibly

adjusted by the Padding attribute). The value of each edge shall be an

array of three numbers in the range 0.0 to 1.0, representing the red,

green, and blue values, respectively, of an RGB colour space. There

are two forms:

A single array of three numbers representing the RGB values to apply

to all four edges.

An array of four arrays, each specifying the RGB values for one edge

of the border, in the order of the before, after, start, and end edges. A

value of null for any of the edges means that it shall not be drawn.

If this attribute is not specified, the border colour for this element shall

be the current text fill colour in effect at the start of its associated

content.

598

Table 343 - Standard layout attributes common to all standard structure types (continued)

Key

Type

Value

BorderStyle

array

or

(Optional; not inheritable; PDF 1.5) The style of an element’s border.

name

Specifies the stroke pattern of each edge of a table cell or any

element’s content rectangle

(possibly adjusted by the Padding

attribute). There are two forms:

•

A name from the list below representing the border style to apply

to all four edges.

•

An array of four entries, each entry specifying the style for one

edge of the border in the order of the before, after, start, and end

edges. A value of null for any of the edges means that it shall not

be drawn.

None No border. Forces the computed value of BorderThickness

to be 0.

Hidden Same as None, except in terms of border conflict resolution

for table elements.

Dotted The border is a series of dots.

Dashed The border is a series of short line segments.

Solid

The border is a single line segment.

Double The border is two solid lines. The sum of the two lines and

the space between them equals the value of

BorderThickness.

Groove The border looks as though it were carved into the canvas.

Ridge The border looks as though it were coming out of the canvas

(the opposite of Groove).

Inset

The border makes the entire box look as though it were

embedded in the canvas.

Outset The border makes the entire box look as though it were

coming out of the canvas (the opposite of Inset).

Default value: None

All borders shall be drawn on top of the box’s background. The colour

of borders drawn for values of Groove, Ridge, Inset, and Outset shall

depend on the structure element’s BorderColor attribute and the

colour of the background over which the border is being drawn.

NOTE

Conforming HTML applications may interpret Dotted,

Dashed, Double, Groove, Ridge, Inset, and Outset to be

Solid.

BorderThickness

number

or

(Optional; inheritable; PDF 1.5) The thickness of the border drawn on

array

the edges of a table cell or any element’s content rectangle (possibly

adjusted by the Padding attribute). The value of each edge shall be a

positive number in default user space units representing the border’s

thickness (a value of 0 indicates that the border shall not be drawn).

There are two forms:

A number representing the border thickness for all four edges.

An array of four entries, each entry specifying the thickness for one

edge of the border, in the order of the before, after, start, and end

edges. A value of null for any of the edges means that it shall not be

drawn.

599

Table 343 - Standard layout attributes common to all standard structure types (continued)

Key

Type

Value

Padding

number or

(Optional; not inheritable; PDF 1.5) Specifies an offset to account for

array

the separation between the element’s content rectangle and the

surrounding border

(see

“Content and Allocation Rectangles” in

14.8.5.4,

“Layout Attributes”). A positive value enlarges the

background area; a negative value trims it, possibly allowing the

border to overlap the element’s text or graphic.

The value shall be either a single number representing the width of the

padding, in default user space units, that applies to all four sides or a

4-element array of numbers representing the padding width for the

before, after, start, and end edge, respectively, of the content

rectangle. Default value: 0.

Color

array

(Optional; inheritable; PDF 1.5) The colour to be used for drawing text

and the default value for the colour of table borders and text

decorations. The value shall be an array of three numbers in the range

0.0 to 1.0, representing the red, green, and blue values, respectively,

of an RGB colour space. If this attribute is not specified, the border

colour for this element shall be the current text fill colour in effect at the

start of its associated content.

14.8.5.4.3

Layout Attributes for BLSEs

Table 344 describes layout attributes that shall apply only to block-level structure elements (BLSEs).

Inline-level structure elements (ILSEs) with a Placement attribute other than the default value of Inline shall be

treated as BLSEs and shall also be subject to the attributes described here.

Table 344 - Additional standard layout attributes specific to

block-level structure elements

Key

Type

Value

SpaceBefore

number

(Optional; not inheritable) The amount of extra space preceding the

before edge of the BLSE, measured in default user space units in the

block-progression direction. This value shall be added to any

adjustments induced by the LineHeight attributes of ILSEs within the

first line of the BLSE (see “Layout Attributes for ILSEs” in 14.8.5.4,

“Layout Attributes”). If the preceding BLSE has a SpaceAfter attribute,

the greater of the two attribute values shall be used. Default value: 0.

This attribute shall be disregarded for the first BLSE placed in a given

reference area.

SpaceAfter

number

(Optional; not inheritable) The amount of extra space following the

after edge of the BLSE, measured in default user space units in the

block-progression direction. This value shall be added to any

adjustments induced by the LineHeight attributes of ILSEs within the

last line of the BLSE (see 14.8.5.4, “Layout Attributes”). If the following

BLSE has a SpaceBefore attribute, the greater of the two attribute

values shall be used. Default value: 0.

This attribute shall be disregarded for the last BLSE placed in a given

reference area.

600

Table 344 - Additional standard layout attributes specific to

block-level structure elements (continued)

Key

Type

Value

StartIndent

number

(Optional; inheritable) The distance from the start edge of the

reference area to that of the BLSE, measured in default user space

units in the inline-progression direction. This attribute shall apply only

to structure elements with a Placement attribute of Block or Start (see

“General Layout Attributes” in

14.8.5.4,

“Layout Attributes”). The

attribute shall be disregarded for elements with other Placement

values. Default value: 0.

A negative value for this attribute places the start edge of the BLSE

outside that of the reference area. The results are implementation-

dependent and may not be supported by all conforming products that

process Tagged PDF or by particular export formats.

If a structure element with a StartIndent attribute is placed adjacent to

a floating element with a Placement attribute of Start, the actual value

used for the element’s starting indent shall be its own StartIndent

attribute or the inline extent of the adjacent floating element, whichever

is greater. This value may be further adjusted by the element’s

TextIndent attribute, if any.

EndIndent

number

(Optional; inheritable) The distance from the end edge of the BLSE to

that of the reference area, measured in default user space units in the

inline-progression direction. This attribute shall apply only to structure

elements with a Placement attribute of Block or End (see “General

Layout Attributes” in 14.8.5.4, “Layout Attributes”). The attribute shall

be disregarded for elements with other Placement values. Default

value: 0.

A negative value for this attribute places the end edge of the BLSE

outside that of the reference area. The results are implementation-

dependent and may not be supported by all conforming products that

process Tagged PDF or by particular export formats.

If a structure element with an EndIndent attribute is placed adjacent to

a floating element with a Placement attribute of End, the actual value

used for the element’s ending indent shall be its own EndIndent

attribute or the inline extent of the adjacent floating element, whichever

is greater.

TextIndent

number

(Optional; inheritable; applies only to some BLSEs) The additional

distance, measured in default user space units in the inline-

progression direction, from the start edge of the BLSE, as specified by

StartIndent, to that of the first line of text. A negative value shall

indicate a hanging indent. Default value: 0.

This attribute shall apply only to paragraphlike BLSEs and those of

structure types Lbl (Label), LBody (List body), TH (Table header), and

TD (Table data), provided that they contain content other than nested

BLSEs.

TextAlign

name

(Optional; inheritable; applies only to BLSEs containing text) The

alignment, in the inline-progression direction, of text and other content

within lines of the BLSE:

Start

Aligned with the start edge.

Center Centered between the start and end edges.

End

Aligned with the end edge.

Justify

Aligned with both the start and end edges, with internal

spacing within each line expanded, if necessary, to achieve

such alignment. The last (or only) line shall be aligned with

the start edge only.

Default value: Start.

601

Table 344 - Additional standard layout attributes specific to

block-level structure elements (continued)

Key

Type

Value

BBox

rectangle

(Optional for Annot; required for any figure or table appearing in its

entirety on a single page; not inheritable) An array of four numbers in

default user space units that shall give the coordinates of the left,

bottom, right, and top edges, respectively, of the element’s bounding

box (the rectangle that completely encloses its visible content). This

attribute shall apply to any element that lies on a single page and

occupies a single rectangle.

Width

number

(Optional; not inheritable; illustrations, tables, table headers, and table

or name

cells only; should be used for table cells) The width of the element’s

content rectangle

(see

“Content and Allocation Rectangles” in

14.8.5.4, “Layout Attributes”), measured in default user space units in

the inline-progression direction. This attribute shall apply only to

elements of structure type Figure, Formula, Form, Table, TH (Table

header), or TD (Table data).

The name Auto in place of a numeric value shall indicate that no

specific width constraint is to be imposed; the element’s width shall be

determined by the intrinsic width of its content. Default value: Auto.

Height

number

(Optional; not inheritable; illustrations, tables, table headers, and table

or name

cells only) The height of the element’s content rectangle (see “Content

and Allocation Rectangles” in 14.8.5.4, “Layout Attributes”), measured

in default user space units in the block-progression direction. This

attribute shall apply only to elements of structure type Figure, Formula,

Form, Table, TH (Table header), or TD (Table data).

The name Auto in place of a numeric value shall indicate that no

specific height constraint is to be imposed; the element’s height shall

be determined by the intrinsic height of its content. Default value: Auto.

BlockAlign

name

(Optional; inheritable; table cells only) The alignment, in the block-

progression direction, of content within the table cell:

Before

Before edge of the first child’s allocation rectangle aligned

with that of the table cell’s content rectangle.

Middle

Children centered within the table cell. The distance

between the before edge of the first child’s allocation

rectangle and that of the table cell’s content rectangle

shall be the same as the distance between the after edge

of the last child’s allocation rectangle and that of the table

cell’s content rectangle.

After

After edge of the last child’s allocation rectangle aligned

with that of the table cell’s content rectangle.

Justify

Children aligned with both the before and after edges of

the table cell’s content rectangle. The first child shall be

placed as described for Before and the last child as

described for After, with equal spacing between the

children. If there is only one child, it shall be aligned with

the before edge only, as for Before.

This attribute shall apply only to elements of structure type TH (Table

header) or TD (Table data) and shall control the placement of all

BLSEs that are children of the given element. The table cell’s content

rectangle

(see

“Content and Allocation Rectangles” in

14.8.5.4,

“Layout Attributes”) shall become the reference area for all of its

descendants. Default value: Before.

602

Table 344 - Additional standard layout attributes specific to

block-level structure elements (continued)

Key

Type

Value

InlineAlign

name

(Optional; inheritable; table cells only) The alignment, in the inline-

progression direction, of content within the table cell:

Start

Start edge of each child’s allocation rectangle aligned with

that of the table cell’s content rectangle.

Center

Each child centered within the table cell. The distance

between the start edges of the child’s allocation rectangle

and the table cell’s content rectangle shall be the same as

the distance between their end edges.

End

End edge of each child’s allocation rectangle aligned with

that of the table cell’s content rectangle.

This attribute shall apply only to elements of structure type TH (Table

header) or TD (Table data) and controls the placement of all BLSEs

that are children of the given element. The table cell’s content

rectangle

(see

“Content and Allocation Rectangles” in

14.8.5.4,

“Layout Attributes”) shall become the reference area for all of its

descendants. Default value: Start.

TBorderStyle

name

or

(Optional; inheritable; PDF 1.5) The style of the border drawn on each

array

edge of a table cell. Allowed values shall be the same as those

specified for BorderStyle (see Table 343). If both TBorderStyle and

BorderStyle apply to a given table cell, BorderStyle shall supersede

TBorderStyle. Default value: None.

TPadding

integer

or

(Optional; inheritable; PDF 1.5) Specifies an offset to account for the

array

separation between the table cell’s content rectangle and the

surrounding border

(see

“Content and Allocation Rectangles” in

14.8.5.4, “Layout Attributes”). If both TPadding and Padding apply to

a given table cell, Padding shall supersede TPadding. A positive

value shall enlarge the background area; a negative value shall trim it,

and the border may overlap the element’s text or graphic. The value

shall be either a single number representing the width of the padding,

in default user space units, that applies to all four edges of the table

cell or a 4-entry array representing the padding width for the before

edge, after edge, start edge, and end edge, respectively, of the content

rectangle. Default value: 0.

14.8.5.4.4

Layout Attributes for ILSEs

The attributes described in Table 345 apply to inline-level structure elements (ILSEs). They may also be

specified for a block-level element (BLSE) and may apply to any content items that are its immediate children.

603

Table 345 - Standard layout attributes specific to inline-level structure elements

Key

Type

Value

BaselineShift

number

(Optional; not inheritable) The distance, in default user space units,

by which the element’s baseline shall be shifted relative to that of its

parent element. The shift direction shall be the opposite of the

block-progression direction specified by the prevailing

WritingMode attribute (see “General Layout Attributes” in 14.8.5.4,

“Layout Attributes”). Thus, positive values shall shift the baseline

toward the before edge and negative values toward the after edge

of the reference area

(upward and downward, respectively, in

Western writing systems). Default value: 0.

The shifted element may be a superscript, a subscript, or an inline

graphic. The shift shall apply to the element, its content, and all of

its descendants. Any further baseline shift applied to a child of this

element shall be measured relative to the shifted baseline of this

(parent) element.

LineHeight

number

(Optional; inheritable) The element’s preferred height, measured in

or name

default user space units in the block-progression direction. The

height of a line shall be determined by the largest LineHeight value

for any complete or partial ILSE that it contains.

The name Normal or Auto in place of a numeric value shall indicate

that no specific height constraint is to be imposed. The element’s

height shall be set to a reasonable value based on the content’s font

size:

Normal Adjust the line height to include any nonzero value

specified for BaselineShift.

Auto

Adjustment for the value of BaselineShift shall not be

made.

Default value: Normal.

This attribute applies to all ILSEs (including implicit ones) that are

children of this element or of its nested ILSEs, if any. It shall not

apply to nested BLSEs.

When translating to a specific export format, the values Normal and

Auto, if specified, shall be used directly if they are available in the

target format. The meaning of the term “reasonable value” is left to

the conforming reader to determine. It should be approximately 1.2

times the font size, but this value can vary depending on the export

format.

NOTE 1

In the absence of a numeric value for LineHeight or

an explicit value for the font size, a reasonable method

of calculating the line height from the information in a

Tagged PDF file is to find the difference between the

associated font’s Ascent and Descent values (see

9.8, “Font Descriptors”), map it from glyph space to

default user space (see 9.4.4, “Text Space Details”),

and use the maximum resulting value for any character

in the line.

TextDecorationColor

array

(Optional; inheritable; PDF 1.5) The colour to be used for drawing

text decorations. The value shall be an array of three numbers in

the range 0.0 to 1.0, representing the red, green, and blue values,

respectively, of an RGB colour space. If this attribute is not

specified, the border colour for this element shall be the current fill

colour in effect at the start of its associated content.

604

Table 345 - Standard layout attributes specific to inline-level structure elements (continued)

Key

Type

Value

TextDecorationThickness

number

(Optional; inheritable; PDF 1.5) The thickness of each line drawn as

part of the text decoration. The value shall be a non-negative

number in default user space units representing the thickness (0 is

interpreted as the thinnest possible line). If this attribute is not

specified, it shall be derived from the current stroke thickness in

effect at the start of the element’s associated content, transformed

into default user space units.

TextDecorationType

name

(Optional; not inheritable) The text decoration, if any, to be applied

to the element’s text.

None

No text decoration

Underline

A line below the text

Overline

A line above the text

LineThrough A line through the middle of the text

Default value: None.

This attribute shall apply to all text content items that are children of

this element or of its nested ILSEs, if any. The attribute shall not

apply to nested BLSEs or to content items other than text.

The colour, position, and thickness of the decoration shall be

uniform across all children, regardless of changes in colour, font

size, or other variations in the content’s text characteristics.

RubyAlign

name

(Optional; inheritable; PDF 1.5) The justification of the lines within a

ruby assembly:

Start

The content shall be aligned on the start edge in the

inline-progression direction.

Center

The content shall be centered in the inline-progression

direction.

End

The content shall be aligned on the end edge in the

inline-progression direction.

Justify

The content shall be expanded to fill the available width

in the inline-progression direction.

Distribute The content shall be expanded to fill the available width

in the inline-progression direction. However, space shall

also be inserted at the start edge and end edge of the

text. The spacing shall be distributed using a

1:2:1

(start:infix:end) ratio. It shall be changed to a 0:1:1 ratio

if the ruby appears at the start of a text line or to a 1:1:0

ratio if the ruby appears at the end of the text line.

Default value: Distribute.

This attribute may be specified on the RB and RT elements. When a

ruby is formatted, the attribute shall be applied to the shorter line of

these two elements. (If the RT element has a shorter width than the

RB element, the RT element shall be aligned as specified in its

RubyAlign attribute.)

605

Table 345 - Standard layout attributes specific to inline-level structure elements (continued)

Key

Type

Value

RubyPosition

name

(Optional; inheritable; PDF 1.5) The placement of the RT structure

element relative to the RB element in a ruby assembly:

Before The RT content shall be aligned along the before edge of

the element.

After

The RT content shall be aligned along the after edge of

the element.

Warichu The RT and associated RP elements shall be formatted

as a warichu, following the RB element.

Inline

The RT and associated RP elements shall be formatted

as a parenthesis comment, following the RB element.

Default value: Before.

GlyphOrientationVertical

name

(Optional; inheritable; PDF 1.5) Specifies the orientation of glyphs

when the inline-progression direction is top to bottom or bottom to

top.

This attribute may take one of the following values:

angle A number representing the clockwise rotation in degrees of

the top of the glyphs relative to the top of the reference area. Shall

be a multiple of 90 degrees between -180 and +360.

AutoSpecifies a default orientation for text, depending on whether it

is fullwidth

(as wide as it is high). Fullwidth Latin and fullwidth

ideographic text (excluding ideographic punctuation) shall be set

with an angle of 0. Ideographic punctuation and other ideographic

characters having alternate horizontal and vertical forms shall use

the vertical form of the glyph. Non-fullwidth text shall be set with an

angle of 90.

Default value: Auto.

NOTE 2

This attribute is used most commonly to differentiate

between the preferred orientation of alphabetic (non-

ideographic) text in vertically written Japanese

documents (Auto or 90) and the orientation of the

ideographic characters and/or alphabetic

(non-

ideographic) text in western signage and advertising

(90).

This attribute shall affect both the alignment and width of the glyphs.

If a glyph is perpendicular to the vertical baseline, its horizontal

alignment point shall be aligned with the alignment baseline for the

script to which the glyph belongs. The width of the glyph area shall

be determined from the horizontal width font characteristic for the

glyph.

14.8.5.4.5

Content and Allocation Rectangles

As defined in 14.8.3, “Basic Layout Model,” an element’s content rectangle is an enclosing rectangle derived

from the shape of the element’s content, which shall define the bounds used for the layout of any included child

elements. The allocation rectangle includes any additional borders or spacing surrounding the element,

affecting how it shall be positioned with respect to adjacent elements and the enclosing content rectangle or

reference area.

The exact definition of the content rectangle shall depend on the element’s structure type:

•

For a table cell (structure type TH or TD), the content rectangle shall be determined from the bounding box

of all graphics objects in the cell’s content, taking into account any explicit bounding boxes (such as the

BBox entry in a form XObject). This implied size may be explicitly overridden by the cell’s Width and

Height attributes. The cell’s height shall be adjusted to equal the maximum height of any cell in its row; its

width shall be adjusted to the maximum width of any cell in its column.

606

Table 346 - Standard column attributes

Key

Type

Value

ColumnCount

integer

(Optional; not inheritable; PDF 1.6) The number of columns in the content

of the grouping element. Default value: 1.

ColumnGap

number

(Optional; not inheritable; PDF 1.6) The desired space between adjacent

or array

columns, measured in default user space units in the inline-progression

direction. If the value is a number, it specifies the space between all

columns. If the value is an array, it should contain numbers, the first

element specifying the space between the first and second columns, the

second specifying the space between the second and third columns, and

so on. If there are fewer than ColumnCount - 1 numbers, the last

element shall specify all remaining spaces; if there are more than

ColumnCount - 1 numbers, the excess array elements shall be ignored.

ColumnWidths

number

(Optional; not inheritable; PDF 1.6) The desired width of the columns,

or array

measured in default user space units in the inline-progression direction. If

the value is a number, it specifies the width of all columns. If the value is

an array, it shall contain numbers, representing the width of each column,

in order. If there are fewer than ColumnCount numbers, the last element

shall specify all remaining widths; if there are more than ColumnCount

numbers, the excess array elements shall be ignored.

14.8.5.5

List Attribute

If present, the ListNumbering attribute, described in Table 347, shall appear in an L (List) element. It controls

the interpretation of the Lbl (Label) elements within the list’s LI (List item) elements (see “List Elements” in

14.8.4.3, “Block-Level Structure Elements”). This attribute may only be defined in attribute objects whose O

(owner) entry has the value List or is one of the format-specific owner names listed in Table 341.

Table 347 - Standard list attribute

Key

Type

Value

ListNumbering

name

(Optional; inheritable) The numbering system used to generate the

content of the Lbl (Label) elements in an autonumbered list, or the symbol

used to identify each item in an unnumbered list. The value of the

ListNumbering shall be one of the following, and shall be applied as

described here.

None

No autonumbering; Lbl elements

(if present) contain

arbitrary text not subject to any numbering scheme

Disc

Solid circular bullet

Circle

Open circular bullet

Square

Solid square bullet

Decimal

Decimal arabic numerals (1-9, 10-99, … )

UpperRoman Uppercase roman numerals (I, II, III, IV, … )

LowerRoman Lowercase roman numerals (i, ii, iii, iv, … )

UpperAlpha Uppercase letters (A, B, C, … )

LowerAlpha Lowercase letters (a, b, c, … )

Default value: None.

The alphabet used for UpperAlpha and LowerAlpha shall be determined

by the prevailing Lang entry

(see

14.9.2,

“Natural Language

Specification”).

The set of possible values may be expanded as Unicode identifies

additional numbering systems. A conforming reader shall ignore any value

not listed in this table; it shall behave as though the value were None.

608

NOTE

This attribute is used to allow a content extraction tool to autonumber a list. However, the Lbl elements within

the table should nevertheless contain the resulting numbers explicitly, so that the document can be reflowed or

printed without the need for autonumbering.

14.8.5.6

PrintField Attributes

(PDF 1.7) The attributes described in Table 348 identify the role of fields in non-interactive PDF forms. Such

forms may have originally contained interactive fields such as text fields and radio buttons but were then

converted into non-interactive PDF files, or they may have been designed to be printed out and filled in

manually. Since the roles of the fields cannot be determined from interactive elements, the roles are defined

using PrintField attributes.

NOTE

PrintField attributes enable screen readers to identify page content that represents form fields (radio buttons,

check boxes, push buttons, and text fields). These attributes enable the controls in print form fields to be

represented in the logical structure tree and to be presented to assistive technology as if they were read-only

interactive fields.

Table 348 - PrintField attributes

Key

Type

Value

Role

name

(Optional; not inheritable) The type of form field represented by this

graphic. The value of Role shall be one of the following, and a conforming

reader shall interpret its meaning as defined herein.

rb

Radio button

cb

Check box

pb Push button

tv

Text-value field

The tv role shall be used for interactive fields whose values have been

converted to text in the non-interactive document. The text that is the

value of the field shall be the content of the Form element (see Table 340).

NOTE 1

Examples include text edit fields, numeric fields, password

fields, digital signatures, and combo boxes.

Default value: None specified.

checked

name

(Optional; not inheritable) The state of a radio button or check box field.

The value shall be one of: on, off (default), or neutral.

NOTE 2

The case (capitalization) used for this key does not conform

to the same conventions used elsewhere in this standard.

Desc

text string

(Optional; not inheritable) The alternate name of the field.

NOTE 3

Similar to the value supplied in the TU entry of the field

dictionary for interactive fields (see Table 220).

14.8.5.7

Table Attributes

The value of the O (owner) entry of a Table attributes element shall be Table or one of the format-specific

owner names listed in Table 341.

609

Table 349 - Standard table attributes

Key

Type

Value

RowSpan

integer

(Optional; not inheritable) The number of rows in the enclosing table that

shall be spanned by the cell. The cell shall expand by adding rows in the

block-progression direction specified by the table’s WritingMode

attribute. If this entry is absent, a conforming reader shall assume a value

of 1.

This entry shall only be used when the table cell has a structure type of

TH or TD or one that is role mapped to structure type TH or TD (see

Table 337).

ColSpan

integer

(Optional; not inheritable) The number of columns in the enclosing table

that shall be spanned by the cell. The cell shall expand by adding

columns in the inline-progression direction specified by the table’s

WritingMode attribute. If this entry is absent, a conforming reader shall

assume a value of 1

This entry shall only be used when the table cell has a structure type of

TH or TD or one that is role mapped to structure types TH or TD (see

Table 337).

Headers

array

(Optional; not inheritable; PDF 1.5) An array of byte strings, where each

string shall be the element identifier (see the ID entry in Table 323) for a

TH structure element that shall be used as a header associated with this

cell.

This attribute may apply to header cells (TH) as well as data cells (TD)

(see Table 337). Therefore, the headers associated with any cell shall be

those in its Headers array plus those in the Headers array of any TH

cells in that array, and so on recursively.

Scope

name

(Optional; not inheritable; PDF 1.5) A name whose value shall be one of

the following: Row, Column, or Both. This attribute shall only be used

when the structure type of the element is TH. (see Table 337). It shall

reflect whether the header cell applies to the rest of the cells in the row

that contains it, the column that contains it, or both the row and the

column that contain it.

Summary

text string

(Optional; not inheritable; PDF 1.7) A summary of the table’s purpose and

structure. This entry shall only be used within Table structure elements

(see Table 337).

NOTE

For use in non-visual rendering such as speech or braille

14.9

Accessibility Support

14.9.1

General

PDF includes several facilities in support of accessibility of documents to users with disabilities. In particular,

many visually computer users with visual impairments use screen readers to read documents aloud. To enable

proper vocalization, either through a screen reader or by some more direct invocation of a text-to-speech

engine, PDF supports the following features:

•

Specifying the natural language used for text in a PDF document—for example, as English or Spanish, or

used to hide or reveal optional content (see 14.9.2, “Natural Language Specification”)

•

Providing textual descriptions for images or other items that do not translate naturally into text (14.9.3,

“Alternate Descriptions”), or replacement text for content that does translate into text but is represented in

a nonstandard way (such as with a ligature or illuminated character; see 14.9.4, “Replacement Text”)

•

Specifying the expansion of abbreviations or acronyms (Section 14.9.5, “Expansion of Abbreviations and

Acronyms”)

610

The information needed to perform these operations shall be recorded in two data structures in the PDF file:

•

The Web Capture information dictionary, which shall hold document-level information related to Web

Capture.

•

The Web Capture content database, which shall hold a complete registry of the source content resources

retrieved by Web Capture and where it came from.

NOTE 3

The Web Capture content database enables the capturing process to avoid downloading material that is

already present in the file.

14.10.2

Web Capture Information Dictionary

The optional SpiderInfo entry in the document catalogue (see 7.7.2, “Document Catalog”), if present, shall hold

Web Capture information dictionary.

Table 350 - Entries in the Web Capture information dictionary

Key

Type

Value

V

number

(Required) The Web Capture version number. The version number shall be 1.0 in a

conforming file.

This value shall be a single real number, not a major and minor version number.

EXAMPLE

A version number of 1.2 would be considered greater than 1.15.

C

array

(Optional) An array of indirect references to Web Capture command dictionaries

(see 14.10.5.3, “Command Dictionaries”) describing commands that were used in

building the PDF file. The commands shall appear in the array in the order in which

they were executed in building the file.

14.10.3

Content Database

14.10.3.1

General

When a PDF file, or part of a PDF file, is built from a content resource stored in another format, such as an

HTML page, the resulting PDF file (or portion thereof) may contain content from more than the single content

resources. Conversely, since many content formats do not have static pagination, a single content resource

may give rise to multiple PDF pages.

To keep track of the correspondence between PDF content and the resources from which the content was

derived, a PDF file may contain a content database that maps URLs and digital identifiers to PDF objects such

as pages and XObjects.

NOTE 4

By looking up digital identifiers in the database, Web Capture can determine whether newly downloaded

content is identical to content already retrieved from a different URL. Thus, it can perform optimizations such

as storing only one copy of an image that is referenced by multiple HTML pages.

Web Capture’s content database shall be organized into content sets. Each content set shall be a dictionary

holding information about a group of related PDF objects generated from the same source data. A content set

shall have for the value of its S (subtype) entry either the value SPS, for a page set, or SIS, for an image set.

The mapping from a source content resource to a content set in a PDF document may be saved in the PDF file.

The mapping may be an association from the resource's URL to the content set, stored in the PDF document's

URLS name tree. The mapping may also be an association from a digital identifier (14.10.3.3, “Digital

Identifiers”) generated from resource's data to the content set, stored in the PDF document's IDS name tree.

Both associations may be present in the PDF file.

617

Document catalog

Dictionary

Name dictionary

Name tree

URLS

IDS

http://www.adobe.com/

904B…1EA2

Page set

Page

Page

Page

Figure 84 - Simple Web Capture file structure

Entries in the URLS and IDS name trees may refer to an array of content sets or a single content set. If the

entry is an array, the content sets need not have the same subtype; the array may include both page sets and

image sets.

618

Document catalog

Dictionary

Names dictionary

Name tree

Array

URLS

IDS

http://www.adobe.com/getacro.gif

BF70…14D8

Content set array

Page set

Image set

Page

Image XObject

Figure 85 - Complex Web Capture file structure

14.10.3.2

URL Strings

URLs associated with Web Capture content sets shall be reduced to a predictable, canonical form before being

used as keys in the URLS name tree. The following steps describe how to perform this reduction, using

terminology from Internet RFCs 1738, Uniform Resource Locators, and 1808, Relative Uniform Resource

Locators (see the Bibliography). This algorithm shall be applied for HTTP, FTP, and file URLs:

Algorithm: URL strings

a) If the URL is relative, it shall be converted into an absolute URL.

b) If the URL contains one or more NUMBER SIGN (02h3) characters, it shall be truncated before the first

NUMBER SIGN.

c) Any uppercase ASCII characters within the scheme section of the URL shall be replaced with the

corresponding lowercase ASCII characters.

d) If there is a host section, any uppercase ASCII characters therein shall be converted to lowercase ASCII.

619

Furthermore, when updating an existing file, a conforming processor shall ensure that each destination or field

is given a unique name that shall be derived from its original name but constructed so that it avoids conflicts

with similarly named items elsewhere.

The unique name shall be formed by appending an encoded form of the page set’s digital identifier string to the

original name of the destination or field. The identifier string shall be encoded to remove characters that have

special meaning in destinations and fields. The characters listed in the first column of Table 351 have special

meaning and shall be encoded using the corresponding byte values from second column of Table 351.

Table 351 - Characters with special meaning in destinations and fields and their byte values

Character

Byte value

Escape sequence

(nul)

0x00

\0 (0x5c 0x30)

(PERIOD)

0x2e

\p (0x5c 0x70)

\

(backslash)

0x5c

\\ (0x5c 0x5c)

EXAMPLE

Since the PERIOD character (2Eh) is used as the field separator in interactive form field names, it does

not appear in the identifier portion of the unique name.

If the name is used for an interactive form field, there is an additional encoding to ensure uniqueness and

compatibility with interactive forms. Each byte in the source string, encoded as described previously, shall be

replaced by two bytes in the destination string. The first byte in each pair is 65 (corresponding to the ASCII

character A) plus the high-order 4 bits of the source byte; the second byte is 65 plus the low-order 4 bits of the

source byte.

14.10.4

Content Sets

14.10.4.1

General

A Web Capture content set is a dictionary describing a set of PDF objects generated from the same source

data. It may include information common to all the objects in the set as well as about the set itself. Table 352

defines the contents of this type of dictionary.

14.10.4.2

Page Sets

A page set is a content set containing a group of PDF page objects generated from a common source, such as

an HTML file. The pages shall be listed in the O array of the page set dictionary (see Table 352) in the same

order in which they were initially added to the file. A single page object shall not belong to more than one page

set. Table 353 defines the content set dictionary entries specific to Page Sets.

The TID (text identifier) entry may be used to store an identifier generated from the text of the pages belonging

to the page set (see 14.10.3.3, “Digital Identifiers”). A text identifier may not be appropriate for some page sets

(such as those with no text) and may be omitted in these cases.

EXAMPLE

This identifier may be used to determine whether the text of a document has changed.

Table 352 - Entries common to all Web Capture content sets

Key

Type

Value

Type

name

(Optional) The type of PDF object that this dictionary describes; if present, shall

be SpiderContentSet for a Web Capture content set.

S

name

(Required) The subtype of content set that this dictionary describes. The value

shall be one of:

SPS

(“Spider page set”) A page set

SIS

(“Spider image set”) An image set

621

Table 352 - Entries common to all Web Capture content sets (continued)

Key

Type

Value

ID

byte string

(Required) The digital identifier of the content set

(see 14.10.3.3,

“Digital

Identifiers”).

O

array

(Required) An array of indirect references to the objects belonging to the

content set. The order of objects in the array is restricted when the content set

subtype (S entry) is SPS (see 14.10.4.2, “Page Sets”).

SI

dictionary

(Required) A source information dictionary (see 14.10.5, “Source Information”)

or array

or an array of such dictionaries, describing the sources from which the objects

belonging to the content set were created.

CT

ASCII string

(Optional) The content type, an ASCII string characterizing the source from

which the objects belonging to the content set were created. The string shall

conform to the content type specification described in Internet RFC 2045,

Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet

Message Bodies (see the Bibliography).

EXAMPLE

for a page set consisting of a group of PDF pages created

from an HTML file, the content type would be text / html.

TS

date

(Optional) A time stamp giving the date and time at which the content set was

created.

Table 353 - Additional entries specific to a Web Capture page set

Key

Type

Value

S

name

(Required) The subtype of content set that this dictionary describes; shall be

SPS.

T

text string

(Optional) The title of the page set, a human-readable text string.

TID

byte string

(Optional) A text identifier generated from the text of the page set, as described

in 14.10.3.3, “Digital Identifiers.”

14.10.4.3

Image Sets

An image set is a content set containing a group of image XObjects generated from a common source, such as

multiple frames of an animated GIF image. A single XObject shall not belong to more than one image set.

Table 354 shows the content set dictionary entries specific to Image Sets.

Table 354 - Additional entries specific to a Web Capture image set

Key

Type

Value

S

name

(Required) The subtype of content set that this dictionary describes; shall be SIS.

R

integer

(Required) The reference counts for the image XObjects belonging to the image

or array

set. For an image set containing a single XObject, the value shall be the integer

reference count for that XObject. For an image set containing multiple XObjects,

the value shall be an array of reference counts parallel to the O array (see

Table 352); that is, each element in the R array shall hold the reference count for

the image XObject at the corresponding position in the O array.

Each image XObject in an image set has a reference count indicating the number of PDF pages referring to

that XObject. The reference count shall be incremented whenever Web Capture creates a new page referring

to the XObject (including copies of already existing pages) and decremented whenever such a page is

destroyed. The reference count shall be incremented or decremented only once per page, regardless of the

number of times the XObject may be referenced by that page. If the reference count reaches 0, it shall be

622

assumed that there are no remaining pages referring to the XObject and that the XObject can be removed from

the image set’s O array. When removing an XObject from the O array of an image set, the corresponding entry

in the R array shall be removed also.

14.10.5

Source Information

14.10.5.1

General

The SI entry in a content set dictionary (see Table 352) shall contain one or more source information

dictionaries, each containing information about the locations from which the source data for the content set was

retrieved.

Table 355 - Entries in a source information dictionary

Key

Type

Value

AU

ASCII string

(Required) An ASCII string or URL alias dictionary (see 14.10.5.2, “URL Alias

or

Dictionaries”) which shall identify the URLs from which the source data was

dictionary

retrieved.

TS

date

(Optional) A time stamp which, if present, shall contain the most recent date

and time at which the content set’s contents were known to be up to date with

the source data.

E

date

(Optional) An expiration stamp which, if present, shall contain the date and time

at which the content set’s contents shall be considered out of date with the

source data.

S

integer

(Optional) A code which, if present, shall indicate the type of form submission, if

any, by which the source data was accessed (see 12.7.5.2, “Submit-Form

Action”). If present, the value of the S entry shall be 0, 1, or 2, in accordance

with the following meanings:

0

Not accessed by means of a form submission

1

Accessed by means of an HTTP GET request

2

Accessed by means of an HTTP POST request

This entry may be present only in source information dictionaries associated

with page sets. Default value: 0.

C

dictionary

(Optional; if present, shall be an indirect reference) A command dictionary (see

14.10.5.3, “Command Dictionaries”) describing the command that caused the

source data to be retrieved. This entry may be present only in source

information dictionaries associated with page sets.

A content set's SI entry may contain a single source information dictionary. However, a PDF processor may

attempt to detect situations in which the same source data has been located via two or more distinct URLs. If a

processor detects such a situation, it may generate a single content set from the source data, containing a

single copy of the relevant PDF pages or image XObjects. In this case, the SI entry shall be an array containing

one source information dictionary for each distinct URL from which the original source content was found.

The determination that distinct URLs produce the same source data shall be made by comparing digital

identifiers for the source data.

A source information dictionary’s AU (aliased URLs) entry shall identify the URLs from which the source data

was retrieved. If there is only one such URL, the v value of this entry may be a string. If multiple URLs map to

the same location through redirection, the AU value shall be a URL alias dictionary (see 14.10.5.2, “URL Alias

Dictionaries”).

NOTE 1

For file size efficiency, the entire URL alias dictionary (excluding the URL strings) should be represented as a

direct object because its internal structure should never be shared or externally referenced.

623

The TS (time stamp) entry allows each source location associated with a content set to have its own time

stamp.

NOTE 2

This is necessary because the time stamp in the content set dictionary (see Table 352) merely refers to the

creation date of the content set. A hypothetical “Update Content Set” command might reset the time stamp in

the source information dictionary to the current time if it found that the source data had not changed since the

time stamp was last set.

The E (expiration) entry specifies an expiration date for each source location associated with a content set. If

the current date and time are later than those specified, the contents of the content set shall be considered out

of date with respect to the original source.

14.10.5.2

URL Alias Dictionaries

When a URL is accessed via HTTP, a response header may be returned indicating that the requested data is at

a different URL. This redirection process may be repeated in turn at the new URL and can potentially continue

indefinitely. It is not uncommon to find multiple URLs that all lead eventually to the same destination through

one or more redirections. A URL alias dictionary represents such a set of URL chains leading to a common

destination. Table 356 shows the contents of this type of dictionary.

Table 356 - Entries in a URL alias dictionary

Key

Type

Value

U

ASCII

(Required) The destination URL to which all of the chains specified by the C entry

string

lead.

C

array

(Optional) An array of one or more arrays of strings, each representing a chain of

URLs leading to the common destination specified by U.

The C (chains) entry may be omitted if the URL alias dictionary contains only one URL. If C is present, its value

shall be an array of arrays, each representing a chain of URLs leading to the common destination. Within each

chain, the URLs shall be stored as ASCII strings in the order in which they occur in the redirection sequence.

The common destination (the last URL in a chain) may be omitted, since it is already identified by the U entry.

14.10.5.3

Command Dictionaries

A Web Capture command dictionary represents a command executed by Web Capture to retrieve one or more

pieces of source data that were used to create new pages or modify existing pages. The entries in this

dictionary represent parameters that were originally specified interactively by the user who requested that the

Web content be captured. This information is recorded so that the command can subsequently be repeated to

update the captured content. Table 357 shows the contents of this type of dictionary.

Table 357 - Entries in a Web Capture command dictionary

Key

Type

Value

URL

ASCII string

(Required) The initial URL from which source data was requested.

L

integer

(Optional) The number of levels of pages retrieved from the initial URL.

Default value: 1.

F

integer

(Optional) A set of flags specifying various characteristics of the

command (see Table 357). Defaut value: 0.

P

string or stream

(Optional) Data that was posted to the URL.

CT

ASCII string

(Optional) A content type describing the data posted to the URL. Default

value: application / x-www-form-urlencoded.

H

string

(Optional) Additional HTTP request headers sent to the URL.

624

Table 357 - Entries in a Web Capture command dictionary (continued)

Key

Type

Value

S

dictionary

(Optional) A command settings dictionary containing settings used in the

conversion process (see 14.10.5.4, “Command Settings”).

The URL entry shall contain the initial URL for the retrieval command. The L (levels) entry shall contain the

number of levels of the hyperlinked URL hierarchy to follow from this URL, creating PDF pages from the

retrieved material. If the L entry is omitted, its value shall be assumed to be 1, denoting retrieval of the initial

URL only.

The value of the command dictionary’s F entry shall be an integer that shall be interpreted as an array of flags

specifying various characteristics of the command. The flags shall be interpreted as defined in Table 358. Only

those flags defined in Table 358 may be set to 1; all other flags shall be 0. Flags not defined in Table 358 are

reserved for future use, and shall not be used by a conforming reader.

NOTE 3

The low-order bit of the flags value is referred to as being at bit-position 1.

Table 358 - Web Capture command flags

Bit position

Name

Meaning

1

SameSite

If set, pages were retrieved only from the host specified in the initial

URL.

2

SamePath

If set, pages were retrieved only from the path specified in the initial

URL.

3

Submit

If set, the command represents a form submission.

The SamePath flag shall be set if the retrieval of source content was restricted to source content in the same

path as specified in the initial URL. Source content shall be considered to be in the same path if its scheme and

network location components (as defined in Internet RFC 1808, Relative Uniform Resource Locators) match

those of the initial URL and its path component matches up to and including the last forward slash ( / ) character

in the initial URL.

EXAMPLE 1

the URL

http : / / www. adobe . com / fiddle / faddle / foo . html

is considered to be in the same path as the initial URL

http : / / www. adobe . com / fiddle /initial . html

The comparison shall be case-insensitive for the scheme and network location components and case-sensitive

for the path component.

The Submit flag shall be set when the command represents a form submission. If no P (posted data) entry is

present, the submitted data shall be encoded in the URL (an HTTP GET request). If P is present, the command

shall be an HTTP POST request. In this case, the value of the Submit flag shall be ignored.

NOTE 4

If the posted data is small enough, it may be represented by a string. For large amounts of data, a stream

should be used because it can be compressed.

The CT (content type) entry shall only be present for POST requests. It shall describe the content type of the

posted data, as described in Internet RFC 2045, Multipurpose Internet Mail Extensions (MIME), Part One:

Format of Internet Message Bodies (see the Bibliography).

625

The H (headers) entry, if present, shall specify additional HTTP request headers that were sent in the request

for the URL. Each header line in the string shall be terminated with a CARRIAGE RETURN and a LINE FEED,

as in this example:

EXAMPLE 2

( Referer : http : / / frumble . com \ 015 \ 012From : veeble@ frotz . com \ 015 \ 012 )

The HTTP request header format is specified in Internet RFC 2616, Hypertext Transfer Protocol—HTTP/1.1

(see the Bibliography).

The S (settings) entry specifies a command settings dictionary (see 14.10.5.4, “Command Settings”). Holding

settings specific to the conversion engines.

14.10.5.4

Command Settings

The S (settings) entry in a command dictionary, if present, shall contain a command settings dictionary, which

holds settings for conversion engines that shall be used in converting the results of the command to PDF.

Table 359 shows the contents of this type of dictionary. If this entry is omitted, default values are assumed.

Command settings dictionaries may be shared by any command dictionaries that use the same settings.

Table 359 - Entries in a Web Capture command settings dictionary

Key

Type

Value

G

dictionary

(Optional) A dictionary containing global conversion engine settings relevant to

all conversion engines. If this entry is absent, default settings shall be used.

C

dictionary

(Optional) Settings for specific conversion engines. Each key in this dictionary is

the internal name of a conversion engine. The associated value is a dictionary

containing the settings associated with that conversion engine. If the settings for

a particular conversion engine are not found in the dictionary, default settings

shall be used.

Each key in the C dictionary represents the internal name of a conversion engine, which shall be a name object

of the following form:

/company : product : version : contentType

where

company denotes the name (or abbreviation) of the company that created the conversion engine.

product denotes the name of the conversion engine. This field may be left blank, but the trailing COLON

character (3Ah) is still required.

version denotes the version of the conversion engine.

contentType denotes an identifier for the content type the associated settings. shall be used because some

converters may handle multiple content types.

EXAMPLE

/ADBE : H2PDF : 1 . 0 : HTML

All fields in the internal name are case-sensitive. The company field shall conform to the naming guidelines

described in Annex E. The values of the other fields shall be unrestricted, except that they shall not contain a

COLON.

The directed graph of PDF objects rooted by the command settings dictionary shall be entirely self-contained;

that is, it shall not contain any object referred to from elsewhere in the PDF file.

NOTE

This facilitates the operation of making a deep copy of a command settings dictionary without explicit

knowledge of the settings it may contain.

626

Headline

Art box

Trim box

Tis might be a caption

Bleed: 10.75x8.25

Trim: 10.5x8

Printer’s marks

Bleed box

Media box

Figure 86 - Page boundaries

NOTE 1

How the various boundaries are used depends on the purpose to which the page is being put. The following

are typical purposes:

Placing the content of a page in another application. The art box determines the boundary of the content that is

to be placed in the application. Depending on the applicable usage conventions, the placed content may be

clipped to either the art box or the bleed box. For example, a quarter-page advertisement to be placed on a

magazine page might be clipped to the art box on the two sides of the ad that face into the middle of the page

and to the bleed box on the two sides that bleed over the edge of the page. The media box and trim box are

ignored.

Printing a finished page. This case is typical of desktop or shared page printers, in which the page content is

positioned directly on the final output medium. The art box and bleed box are ignored. The media box may be

used as advice for selecting media of the appropriate size. The crop box and trim box, if present, should be the

same as the media box.

Printing an intermediate page for use in a prepress process. The art box is ignored. The bleed box defines the

boundary of the content to be imaged. The trim box specifies the positioning of the content on the medium; it

may also be used to generate cut or fold marks outside the bleed box. Content falling within the media box but

outside the bleed box may or may not be imaged, depending on the specific production process being used.

629

Building an imposition of multiple pages on a press sheet. The art box is ignored. The bleed box defines the

clipping boundary of the content to be imaged; content outside the bleed box is ignored. The trim box specifies

the positioning of the page’s content within the imposition. Cut and fold marks are typically generated for the

imposition as a whole.

NOTE 2

In the preceding scenarios, an application that interprets the bleed, trim, and art boxes for some purpose

typically alters the crop box so as to impose the clipping that those boxes prescribe.

14.11.2.2

Display of Page Boundaries

Conforming readers may offer the ability to display guidelines on the screen for the various page boundaries.

The optional BoxColorInfo entry in a page object (see 7.7.3.3, “Page Objects”) holds a box colour information

dictionary (PDF 1.4) specifying the colours and other visual characteristics to be used for such display.

Conforming readers typically provide a user interface to allow the user to set these characteristics interactively.

NOTE

This information is page-specific and may vary from one page to another.

As shown in Table 360, the box colour information dictionary contains an optional entry for each of the possible

page boundaries other than the media box. The value of each entry is a box style dictionary, whose contents

are shown in Table 361. If a given entry is absent, the conforming reader shall use its own current default

settings instead.

14.11.3

Printer’s Marks

Printer’s marks are graphic symbols or text added to a page to assist production personnel in identifying

components of a multiple-plate job and maintaining consistent output during production. Examples commonly

used in the printing industry include:

•

Registration targets for aligning plates

•

Gray ramps and colour bars for measuring colours and ink densities

•

Cut marks showing where the output medium is to be trimmed

Although conforming writers traditionally include such marks in the content stream of a document, they are

logically separate from the content of the page itself and typically appear outside the boundaries (the crop box,

trim box, and art box) defining the extent of that content (see 14.11.2, “Page Boundaries”).

Printer’s mark annotations (PDF 1.4) provide a mechanism for incorporating printer’s marks into the PDF

representation of a page, while keeping them separate from the actual page content. Each page in a PDF

document may contain any number of such annotations, each of which represents a single printer’s mark.

NOTE 1

Because printer’s marks typically fall outside the page’s content boundaries, each mark is represented as a

separate annotation. Otherwise—if, for example, the cut marks at the four corners of the page were defined in

a single annotation—the annotation rectangle would encompass the entire contents of the page and could

interfere with the user’s ability to select content or interact with other annotations on the page. Defining

printer’s marks in separate annotations also facilitates the implementation of a drag-and-drop user interface for

specifying them.

Table 360 - Entries in a box colour information dictionary

Key

Type

Value

CropBox

dictionary

(Optional) A box style dictionary

(see Table 361) specifying the visual

characteristics for displaying guidelines for the page’s crop box. This entry

shall be ignored if no crop box is defined in the page object.

BleedBox

dictionary

(Optional) A box style dictionary

(see Table 361) specifying the visual

characteristics for displaying guidelines for the page’s bleed box. This entry

shall be ignored if no bleed box is defined in the page object.

630

Table 360 - Entries in a box colour information dictionary (continued)

Key

Type

Value

TrimBox

dictionary

(Optional) A box style dictionary

(see Table 361) specifying the visual

characteristics for displaying guidelines for the page’s trim box. This entry

shall be ignored if no trim box is defined in the page object.

ArtBox

dictionary

(Optional) A box style dictionary

(see Table 361) specifying the visual

characteristics for displaying guidelines for the page’s art box. This entry

shall be ignored if no art box is defined in the page object.

Table 361 - Entries in a box style dictionary

Key

Type

Value

C

array

(Optional) An array of three numbers in the range 0.0 to 1.0, representing the

components in the DeviceRGB colour space of the colour to be used for

displaying the guidelines. Default value: [ 0.0

0.0 0.0 ].

W

number

(Optional) The guideline width in default user space units. Default value: 1.

S

name

(Optional) The guideline style:

S

(Solid) A solid rectangle.

D

(Dashed) A dashed rectangle. The dash pattern shall be specified by the

D entry.

Other guideline styles may be defined in the future. Default value: S.

D

array

(Optional) A dash array defining a pattern of dashes and gaps to be used in

drawing dashed guidelines (guideline style D). The dash array shall be

specified in default user space units, in the same format as in the line dash

pattern parameter of the graphics state (see 8.4.3.6, “Line Dash Pattern”).

The dash phase shall not be specified and shall be assumed to be 0.

EXAMPLE

A D entry of [ 3 2 ] specifies guidelines drawn with 3-point

dashes alternating with 2-point gaps.

Default value: [ 3 ].

The visual presentation of a printer’s mark shall be defined by a form XObject specified as an appearance

stream in the N

(normal) entry of the printer’s mark annotation’s appearance dictionary

(see

12.5.5,

“Appearance Streams”). More than one appearance may be defined for the same printer’s mark to meet the

requirements of different regions or production facilities. In this case, the appearance dictionary’s N entry holds

a subdictionary containing the alternate appearances, each identified by an arbitrary key. The AS (appearance

state) entry in the annotation dictionary designates one of them to be displayed or printed.

NOTE 2

The printer’s mark annotation’s appearance dictionary may include R (rollover) or D (down) entries, but

appearances defined in either of these entries are never displayed or printed.

Like all annotations, a printer’s mark annotation shall be defined by an annotation dictionary (see 12.5.2,

“Annotation Dictionaries”); its annotation type is PrinterMark. The AP (appearances) and F (flags) entries

(which ordinarily are optional) shall be present, as shall the AS (appearance state) entry if the appearance

dictionary AP contains more than one appearance stream. The Print and ReadOnly flags in the F entry shall be

set and all others clear (see 12.5.3, “Annotation Flags”). Table 362 shows an additional annotation dictionary

entry specific to this type of annotation.

631

Table 362 - Additional entries specific to a printer’s mark annotation

Key

Type

Value

Subtype

name

(Required) The type of annotation that this dictionary describes; shall be

PrinterMark for a printer’s mark annotation.

MN

name

(Optional) An arbitrary name identifying the type of printer’s mark, such as

ColorBar or RegistrationTarget.

The form dictionary defining a printer’s mark may contain the optional entries shown in Table 363 in addition to

the standard ones common to all form dictionaries (see 8.10.2, “Form Dictionaries”).

Table 363 - Additional entries specific to a printer’s mark form dictionary

Key

Type

Value

MarkStyle

text string

(Optional; PDF 1.4) A text string representing the printer’s mark in

human-readable form and suitable for presentation to the user.

Colorants

dictionary

(Optional; PDF 1.4) A dictionary identifying the individual colorants

associated with a printer’s mark, such as a colour bar. For each

entry in this dictionary, the key is a colorant name and the value is an

array defining a Separation colour space for that colorant (see

8.6.6.4,

“Separation Colour Spaces”). The key shall match the

colorant name given in that colour space.

14.11.4

Separation Dictionaries

In high-end printing workflows, pages are ultimately produced as sets of separations, one per colorant (see

8.6.6.4, “Separation Colour Spaces”). Ordinarily, each page in a PDF file shall be treated as a composite page

that paints graphics objects using all the process colorants and perhaps some spot colorants as well. In other

words, all separations for a page shall be generated from a single PDF description of that page.

In some workflows, however, pages are preseparated before generating the PDF file. In a preseparated PDF

file, the separations for a page shall be described as separate page objects, each painting only a single

colorant (usually specified in the DeviceGray colour space). In this case, additional information is needed to

identify the actual colorant associated with each separation and to group together the page objects

representing all the separations for a given page. This information shall be contained in a separation dictionary

(PDF 1.3) in the SeparationInfo entry of each page object (see 7.7.3.3, “Page Objects”). Table 364 shows the

contents of this type of dictionary.

Table 364 - Entries in a separation dictionary

Key

Type

Value

Pages

array

(Required) An array of indirect references to page objects representing

separations of the same document page. One of the page objects in the

array shall be the one with which this separation dictionary is associated,

and all of them shall have separation dictionaries

(SeparationInfo

entries) containing Pages arrays identical to this one.

DeviceColorant

name or

(Required) The name of the device colorant to be used in rendering this

string

separation, such as Cyan or PANTONE 35 CV.

632

Content      ..     14      15      16      17     ..