SVG Print 1.2, Part 2: Language

Abstract

This Working Draft defines features of the Scalable Vector Graphics (SVG) Language that are specifically for printing environments.

Status of This Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

This document is a Last Call Working Draft. The W3C Membership and other interested parties are invited to review the document and send comments to to public-svg-print@w3.org (archives) until 8 February 2008. There is an accompanying SVG Print 1.2, Part 1: Primer that lists the ways SVG Print, along with other SVG documents, may be used for SVG Printing.

This document has been produced by the W3C SVG Working Group as part of the W3C Graphics Activity within the Interaction Domain. The Working Group expects to advance this Working Draft to Recommendation Status.

Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

How to read this document and give feedback

This draft of SVG Print is a snapshot of a work-in-progress.

The main purpose of this document is to encourage public feedback. The best way to give feedback is by sending an email to public-svg-print@w3.org. Please identify in the subject line of your message the part of the specificationto which your comment refers (e.g "Print compositing" or "Print render formats"). If you have comments on multiple areas of this document, then it is preferable to send several separate comments.

The public are welcome to comment on any aspect in this document, but there are a few areas in which the SVG Working Group are explicitly requesting feedback. These areas are noted in place within this document. There is also a specific area related to the specification that is listed here:

Interaction with other print standards. The SVG Working Group believe that some design decisions would be best made in collaboration with other print standards bodies, and would welcome liaison statements in this area.

Table of Contents

• 1 Introduction
• 2 User Agents
• 3 Printing using Pages
  • 3.1 The pageSet element
  • 3.2 The page element
  • 3.3 The masterPage element
  • 3.4 The rendering-order attribute
  • 3.5 Default Master Pages
  • 3.6 Job Control
  • 3.7 Printing Pages
  • 3.8 The page-orientation property
  • 3.9 The use-master-page attribute
  • 3.10 The print-display attribute
  • 3.11 CSS and pages
• 4 Animation and Scripting
• 5 Color
  • 5.1 Color interpolation
  • 5.2 Specifying paint
    • 5.2.1 sRGB colors
    • 5.2.2 ICC colors
    • 5.2.3 Named color
    • 5.2.4 Uncalibrated device colors
  • 5.3 Color profile descriptions
    • 5.3.1 Overview of color profile descriptions
    • 5.3.2 Alternative ways for defining a color profile description
    • 5.3.3 The 'color-profile' element
    • 5.3.4 @color-profile when using CSS styling
    • 5.3.5 'color-profile' property
  • 5.4 deviceColor Element
• 6 Definitions
• 7 References
  • 7.1 Normative References
  • 7.2 Informative References

1 Introduction

This document lists features that may be used in the context of printing. The various usage scenarios are listed in the SVG Print Requirements document.

This document is normative.

This document contains explicit conformance criteria that overlap with some RNG definitions in requirements. If there is any conflict between the two, the explicit conformance criteria are the definitive reference.

This document contains conformance criteria for a number of different entities:

• The Content (ie. conformance criteria on the document author).
• A User Agent for Printing.
• A User Agent for Print Preview.

Some conformance criteria allow or require the User Agent for Printing and the User Agent for Print Preview to communicate with each other.

The conformance criteria have awkward names - any suggestions for replacing "A User Agent for Printing", "A User Agent for Print Preview", and "A User Agent for Printing or Print Preview" would be welcome.

2 User Agents

3 Printing using Pages

3.1 The pageSet element

The pageSet element is the container for a set of page elements.

    <define name='pageSet'>
      <element name='pageSet'>
        <ref name='pageSet.AT'/>
        <zeroOrMore><ref name='page'/></zeroOrMore>
      </element>
    </define>

    <define name='pageSet.AT' combine='interleave'>
      <ref name='svg.Core.attr'/>
    </define>
    

3.2 The page element

The page element appears only as a child of a pageSet element.

    <define name='page'>
      <element name='page'>
        <ref name='page.AT'/>
        <zeroOrMore><ref name='svg.G.group'/></zeroOrMore>
      </element>
    </define>

    <define name='page.AT' combine='interleave'>
      <ref name='svg.Core.attr'/>
      <ref name='svg.page-orientation.attr'/>
    </define>
    

Conceptually, the page element is similar to an svg element but without transformation and positioning. All pages are in the coordinate system of their pageSet, which is in the coordinate system of the root svg element.

3.3 The masterPage element

The masterPage element appears only as a child of a pageSet element.

    <define name='masterPage'>
      <element name='masterPage'>
        <ref name='masterPage.AT'/>
        <zeroOrMore><ref name='svg.G.group'/></zeroOrMore>
      </element>
    </define>

    <define name='masterPage.AT' combine='interleave'>
      <ref name='svg.Core.attr'/>
      <ref name='svg.rendering-order.attr'/>
    </define>
    

3.4 The rendering-order attribute

A Foreground Master Page is a Master Page with rendering-order set to "over".

A Background Master Page is a Master Page with rendering-order set to "under".

It is possible to have multiple Background Master Pages and/or Foreground Master Pages in an SVG Print document, though only one of each can be active at any given time. Whenever the renderer encounters a Background or Foreground Master Page, it replaces the current Background or Foreground Master Page with the new one, and subsequent pages use the newer one.

3.5 Default Master Pages

The default master pages are made available as a simple default that gives sensible printing behaviour for documents that do not have pageSet elements.

Note that, as a consequence of the foregoing conformance statements, the default background master page (all the elements between the svg element and the pageSet element) is no longer used as a default master page when another background master page is set. Elements in the defs element of an svg document will be available to all pages in the pageSet element.

3.6 Job Control

3.7 Printing Pages

If an SVG document fragment with multiple pages is embedded in, or referenced by, a document from another namespace, such as XHTML, then typically it is up to that namespace to define the processing of pages.

3.8 The page-orientation property

The orientation of each page element can be controlled by the page-orientation property. This enables the content to define whether a portrait or landscape mode is used for display and printing.

When displaying a page on a User Agent for Print Preview, the value of the page-orientation property introduces the following transform before the top-level viewport transformation:

0

No additional transform

-90 or 270

translate(0 height) rotate(-90)

180 or -180

translate(width height) rotate(180)

90 or -270

translate(width 0) rotate(90)

The values for width and height are the dimensions of the top-level viewBox in the user coordinate system or the dimensions of the top-level viewport if there is no viewBox specified.

3.9 The use-master-page attribute

Both the current Foreground Master Page and Background Master Page of the referencing document must be used when use-master-page is set to current.

Both the current Foreground Master Page and Background Master Page of the externally referenced document must be used when use-master-page is set to external.

By default, if the use-master-page attribute is not specified on the use element referencing an external page, then both the current Foreground Master Page and Background Master Page of the referencing document must be used.

TODO: Need feedback on this feature. Are there compelling uses cases for having this extra complexity? What benefit does it provide?

3.10 The print-display attribute

3.11 CSS and pages

4 Animation and Scripting

5 Color

SVG Print extends the control of color, relative to SVG Tiny 1.2, in two ways. Firstly by adding an additional color space for interpolation and compositing; this means that colors are no longer constrained to the sRGB gamut. Secondly by extending the syntax for Paint, thus allowing colors to be specified as calibrated (ICC and named) and uncalibrated ('device') color.

5.1 Color interpolation

The color-interpolation property, not in SVG Tiny 1.2 but used in SVG 1.1 [SVG11], is extended by this specification to add new values using the CIE L*a*b* color space. Both the cartesian (CIE-Lab) and polar (CIE-LCHab) forms are supported.

auto

Indicates that the user agent can choose any of the color spaces - sRGB, linearRGB, CIE-Lab or CIE-LCHab- for color interpolation. This option indicates that the author doesn't require that color interpolation occur in a particular color space.

sRGB

Indicates that color interpolation must occur in the sRGB color space defined by [sRGB].

linearRGB

Indicates that color interpolation must occur in the linearized RGB color space (sRGB with a linear transfer function) as defined in [sRGB].

CIE-Lab

Indicates that color interpolation must occur in the cartesian L*a*b* color space defined by [CIE15].

CIE-LCHab

Indicates that color interpolation must occur in the polar L*CH_ab color space defined by [CIE15].

The 'color-interpolation' property specifies the color space for gradient interpolations and alpha compositing.

When a child element is blended into a background, the value of the 'color-interpolation' property on the child determines the type of blending, not the value of the 'color-interpolation' on the parent.

5.2 Specifying paint

The definition of paint in SVG Tiny 1.2 [SVGT12] is extended by this specification to add the icc-color values from paint in SVG Full 1.1 [SVG11] and also to add new values for named colors and uncalibrated (device) colors.

none

Indicates that no paint shall be applied.

currentColor

Indicates that painting shall be done using the color specified by the current value of the 'color' property. This mechanism is provided to facilitate sharing of color attributes between parent grammars such as other (non-SVG) XML. This mechanism allows you to define a style in your HTML which sets the 'color' property and then pass that style to the SVG user agent so that your SVG text will draw in the same color.

<color>

the explicit color (in the sRGB [rRGB] color space, see sRGB colors).

<color> icc-color(<name> [,<icccolorvalue>]*)

Indicates that the user agent searches the color profile description database for a color profile description entry whose name descriptor matches <name> and uses the last matching entry that is found; painting shall be done using the given ICC color, where the comma-separated list (with optional white space) of <icccolorvalue>'s is a set of ICC-profile-specific color values, expressed as <number>s (see ICC colors). If no match is found, then the fallback sRGB color is used.

<color> icc-named-color(<name>, <namedColor>)

Indicates that the user agent searches the color profile description database for a color profile description entry whose name descriptor matches <name> and uses the last matching entry that is found; painting shall be done using the given ICC color, where namedColor is a <strinf> indicating the named color to use.

<color> device-color(<name> [,<devicecolorvalue>]*)

Indicates that the user agent searches the device color description database for a deviceColor element entry whose name descriptor matches <name> and uses the last matching entry that is found; painting shall be done using the given the device color, where the data of <devicecolorvalue> is a value or set of values understood by the device that recognises the namesapce of the deviceColor element. If no match is found, then the fallback sRGB color is used.

TODO: Need feedback on this feature. Looking into the possibility of having ICC or Name ICC fallback for Device Color as well. ICC or Named ICC should have priority over an sRGB fallback if both types of fallback are specified.

<FuncXMLRI> [ none | currentColor | <color>]

The <FuncXMLRI> specifies a paint server such as a gradient. The fragment identifier of the <FuncXMLRI> provides a link to the paint server (e.g., a gradient or 'solidColor' ) that shall be used to paint the current object. The IRI reference must be a Local IRI reference . If the Local IRI reference is not valid (e.g., it points to an object that doesn't exist or the object is not a valid paint server), then the fallback value (if specified) is used; otherwise it must be treated as if none was specified.

<system paint>

A System Paint Server

Note that by default, color interpolation occurs in the sRGB color space, even if an ICC-based color specification is provided, unless the 'color-interpolation' property is set to one of the CIE Lab color spaces. If an sRGB color interpolation space is specified, all ICC-based colors used for the interpolation must be converted into the sRGB interpolation colorspace.

5.2.1 sRGB colors

As with SVG Tiny 1.2, colors may be specified in the sRGB color space (see [sRGB]). Since all SVG Print and SVG Print Preview User Agents are color management capable, the rendering requirements are more strict than for SVG User Agents [SVG11] where color management is optional.

5.2.2 ICC colors

As with SVG Full 1.1, SVG Print content may specify color using an ICC profile (see [ICC42]). For resiliency and for compatibility with SVG Tiny 1.2, an sRGB fallback must still be provided.

5.2.3 Named color

SVG Print introduces the ability to specify a color using a 'Named Color Profile'.

5.2.4 Uncalibrated device colors

SVG Print also introduces a method of specifying uncallibrated device colors. This is sometimes useful in print workflows. This feature utilises the deviceColor element and the device-color keyword.

As these are uncalibrated, any interpolation or compositing occurs using the fallback sRGB color space

TODO: Need feedback on this feature. Looking into the possibility of having ICC or Name ICC fallback for Device Color as well. ICC or Named ICC should have priority over an sRGB fallback if both types of fallback are specified.

5.3 Color profile descriptions

5.3.1 Overview of color profile descriptions

The International Color Consortium has established a standard, the ICC Profile [ICC32], for documenting the color characteristics of input and output devices. Using these profiles, it is possible to build a transform and correct visual data for viewing on different devices.

A color profile description provides the bridge between an ICC profile and references to that ICC profile within SVG content. The color profile description is added to the user agent's list of known color profiles and then used to select the relevant profile. The color profile description contains descriptors for the location of the color profile on the Web, a name to reference the profile and information about rendering intent.

5.3.2 Alternative ways for defining a color profile description

Color profile descriptions can be specified in either of the following ways:

• a 'color-profile' element
• an @color-profile rule within a CSS style sheet (only applicable for user agents which support using CSS [CSS2] to style the SVG content)

5.3.3 The 'color-profile' element

    <define name='color-profile'>
      <element name='color-profile'>
        <ref name='color-profile.AT'/>
        <empty/>
      </element>
    </define>

    <define name='color-profile.AT' combine='interleave'>
      <ref name='svg.Core.attr'/>
      <ref name='svg.local.attr'/>
      <ref name='svg.name.attr'/>
      <ref name='svg.rendering-intent.attr'/>
    </define>
    

5.3.4 @color-profile when using CSS styling

When the document is styled using CSS, the @color-profile rule can be used to specify a color profile description. The general form is:

@color-profile { <color-profile-description> }

where the <color-profile-description> has the form:

descriptor: value;
[...]
descriptor: value;

Each @color-profile rule specifies a value for every color profile descriptor, either implicitly or explicitly. Those not given explicit values in the rule take the initial value listed with each descriptor in this specification. These descriptors apply solely within the context of the @color-profile rule in which they are defined, and do not apply to document language elements. Thus, there is no notion of which elements the descriptors apply to, or whether the values are inherited by child elements.

The following are the descriptors for a <color-profile-description>:

sRGB

The source profile is the sRGB color space. For consistency with CSS lexical scanning and parsing rules, the keyword "sRGB" is case-insensitive; however, it is recommended that the mixed capitalization "sRGB" be used for consistency with common industry practice.

<local-profile>

The source profile is a locally-stored profile. The syntax for <local-profile> is:

"local(" + <string> + ")"

where <string> is the profile's unique ID as specified by International Color Consortium. (Note: Profile description fields do not represent a profile's unique ID. With current ICC proposals, the profile's unique ID is an MD5-encoded value within the profile header.)

<iri>

The source profile is a IRI reference to a color profile.

(<local-profile> <iri>)

Two profiles are specified. If <local-profile> cannot be found on the local system, then the <iri> is used.

<name>

See the description for the name attribute on the 'color-profile' element. Note that if <name> is not provided, it will be impossible to reference the given @color-profile definition.

See the description for the rendering-intent attribute on the 'color-profile' element.

5.3.5 'color-profile' property

auto

This is the default behavior. All colors are presumed to be defined in the sRGB color space unless a more precise embedded profile is specified within content data. For images that do have a profile built into their data, that profile is used. For images that do not have a profile, the sRGB profile is used.

sRGB

The source profile is assumed to be sRGB. This differs from auto in that it overrides an embedded profile inside an image.

For consistency with CSS lexical scanning and parsing rules, the keyword "sRGB" is case-insensitive; however, it is recommended that the mixed capitalization "sRGB" be used for consistency with common industry practice.

<name>

A name corresponding to a defined color profile that is in the user agent's color profile description database. The user agent searches the color profile description database for a color profile description entry whose name descriptor matches <name> and uses the last matching entry that is found. If a match is found, the corresponding profile overrides an embedded profile inside an image. If no match is found, then the embedded profile inside the image is used.

<iri>

A IRI reference to the source color profile. The referenced color profile overrides an embedded profile inside the image.

5.4 deviceColor Element

Certain print applications can improve printing quality by specifying colors by name or in an alternative color format. This is commonly referred to as using 'spot' colors, device colors or inks, and usually means that a particular ink will be used for the color when it is printed. Furthermore, there are applications in the printing press industry where presses can be set up with different inks for different jobs. This means that the content creator will need to create content tailored to the particular press setup in order to obtain the best results.

The deviceColor element can be used to indicate an alternative color for a particular paint. This element will be mostly used in closed workflows, since the names of the inks and the parameters (percentages of each ink's color components) rarely have meaning outside the domain of the target device.

<xs:element name="deviceColor">
  <xs:complexType>

    <xs:attribute ref="href" use="required"
        namespace="http://www.w3.org/1999/xlink"/>
    <xs:attribute ref="name" use="required" type="string"/>
    <xs:anyAttribute namespace="##any" processContents="skip"/>
  </xs:complexType>
</xs:element>      

xlink:href

A URI used to identify the device-specific information included in this element. If the User Agent does not recognize the URI (ie. is not able to recognize the particular device parameters) then the element should be ignored and should not be part of the rendering process.

Animatable:

no

name

The name of this device-specific color information. The name attribute is used within the device-color specification within <paint> to reference this deviceColor element.

Animatable:

no

The deviceColor element uses attributes from external namespaces to define the device specific properties that are to be used when the deviceColor is referenced from a <paint>.

The following example illustrates the use of deviceColor. There are two things to note:

1. The deviceColor element describes device specific setup information.
2. The device-color keyword is used as an alternative <paint> specification, achieving the desired <paint> when the output is the named device (or when the User Agent is able to understand the device specific information).

<svg xmlns="http://www.w3.org/2000/svg" version="1.2"
     xmlns:xlink="http://www.w3.org/1999/xlink"
     xmlns:ecpi="http://www.example.com/press/inks">

  <defs>
     <!-- describe a particular output device -->
     <deviceColor name="device-inks"
                  xlink:href="http://www.example.com/pressInks"
             ecpi:value="Cyan, Magenta, Yellow, Black, Silver, Gray, Green"/>
  </defs>

  <text x="100" y="150" font-family="Verdana" font-size="35"
        fill="rgb(22,33,44) device-color(device-inks, 11,55,66,77,0,0,88)" >

     Hello, out there

  </text>

</svg>    

In the example above, a supplemental attribute, value, from a private namespace has been added. This example value attribute provides the definitions of colors or inks to be interpreted in the context of the URI specified. It is in a private namespace so that content and context authors can use any understood format to convey the necessary information. When the particular deviceColor element is referenced later by a device-color keyword specification, it is generally expected that the number of parameters following the name reference (1st parameter) in the function-like representation for the value of device-color alternate in a fill or stroke attribute (for example) will have an understood one-to-one correspondence with the information specified for the value attribute in the the deviceColor element. The interpretation of the parameters is implied specifically by the context set by the URI.

6 Definitions

color appearance

Color-appearance models extend basic colorimetry, as defined by CIE tristimulus values, to the prediction of color matches and color appearance across varying viewing conditions.

gamut

The subset of colors which can be accurately represented in a given colorspace or on a given output device.

7 References

7.1 Normative References

[CIE15]

International Commission on Illumination (CIE). Colorimetry, 3rd Edition. Publication CIE 15:2004, ISBN 3-901-906-33-9
Available at http://www.cie.co.at/publ/abst/15-2004.html

[ICC42]

International Color Consortium. Specification ICC.1:2004-10 (Profile version 4.2.0.0) Image technology colour management — Architecture, profile format, and data structure.
Available at http://www.color.org/ICC1V42.pdf

[SRGB]

IEC 61966-2-1 (1999-10) - "Multimedia systems and equipment - Colour measurement and management - Part 2-1: Colour management - Default RGB colour space - sRGB, ISBN: 2-8318-4989-6 ­ ICS codes: 33.160.60, 37.080 ­ TC 100 ­ 51 pp.
Available at: http://domino.iec.ch/webstore/webstore.nsf/artnum/025408.

[SVG12]

Scalable Vector Graphics (SVG) 1.2 Specification, Dean Jackson editor, W3C, 27 October 2004 (Working Draft). See http://www.w3.org/TR/2004/WD-SVG12-20041027/

7.2 Informative References

[SVG11]

Scalable Vector Graphics (SVG) 1.1, J. Ferraiolo, 藤沢 淳 (Fujisawa Jun), D. Jackson, eds. World Wide Web Consortium,14 January 2003.
Latest version available at: http://www.w3.org/TR/SVG11/

[SVG12Reqs]

SVG 1.1/1.2/2.0 Requirements, Dean Jackson editor, W3C, 22 April 2002 (Working Draft). See http://www.w3.org/TR/2002/WD-SVG2Reqs-20020422/

[SVGPrintReqs]

SVG Printing Requirements, Jun Fujisawa, Lee Klosterman Craig Brown, Alex Danilo editors, W3C, 18 February 2003 (Working Draft). See http://www.w3.org/TR/2003/WD-SVGPrintReqs-20030218/

[SVG12PrintPrimer]

SVG Print 1.2 Primer, Anthony Grasso, Andrew Shellshear, Chris Lilley, editors, W3C, 21 December 2007 (Working Draft). See http://www.w3.org/TR/2007/WD-SVGPrintPrimer12-20071221/