Moini: Fix heading levels

2021-06-03T15:26:46Z

Fix heading levels

Tavmjong: /* Add support to Cairo for exporting mesh shading to PDF */

2021-06-03T15:22:18Z

Add support to Cairo for exporting mesh shading to PDF

← Older revision		Revision as of 15:22, 3 June 2021
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	The algorithm for Gouraud shading is in many books on computer graphics.		The algorithm for Gouraud shading is in many books on computer graphics.

	Tav: There should be no need to write out meshes as triangle meshes or in rendering them. PostScript (Level 3) and PDF already directly support mesh gradients.		<span style="color:darkred">Tav: There should be no need to write out meshes as triangle meshes or in rendering them. PostScript (Level 3) and PDF already directly support mesh gradients.</span>

	'''TODO:'''<br>		'''TODO:'''<br>

Tavmjong: /* Add support to Cairo for exporting mesh shading to PDF */

2021-06-03T15:20:06Z

Add support to Cairo for exporting mesh shading to PDF

← Older revision		Revision as of 15:20, 3 June 2021
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	The algorithm for Gouraud shading is in many books on computer graphics.		The algorithm for Gouraud shading is in many books on computer graphics.

			Tav: There should be no need to write out meshes as triangle meshes or in rendering them. PostScript (Level 3) and PDF already directly support mesh gradients.

	'''TODO:'''<br>		'''TODO:'''<br>

Moini: Add Bryce's CMYK / Color management project writeup with his permission.

2021-06-03T13:18:20Z

Add Bryce's CMYK / Color management project writeup with his permission.

Show changes

← Older revision		Revision as of 15:26, 3 June 2021
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	=== Overview ===		== Overview ==

	This plan, developed by Bryce Harrington, defines how print services functionality could be added to Inkscape. This would include strong CMYK support, a Pre-flight checking feature, and improved PDF version support, among other things.		This plan, developed by Bryce Harrington, defines how print services functionality could be added to Inkscape. This would include strong CMYK support, a Pre-flight checking feature, and improved PDF version support, among other things.
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	The overall effort is broken into several discrete projects that can be undertaken semi-independently. Some of the projects will need to wait until post-1.0 for landing in the Inkscape codebase, but prototypes and code targeting Inkscape dependencies like Cairo and Pixman can be landed independently of Inkscape's release schedule.		The overall effort is broken into several discrete projects that can be undertaken semi-independently. Some of the projects will need to wait until post-1.0 for landing in the Inkscape codebase, but prototypes and code targeting Inkscape dependencies like Cairo and Pixman can be landed independently of Inkscape's release schedule.

	=== Background ===		== Background ==

	For Inkscape, "CMYK support" has been a frequent request by end users, needing some degree of color management for PDF export. Naively this might sound trivial - just add support for one more way to enter color values. Indeed, Inkscape already has a CMYK tab in the Fill and Stroke dialog for doing this. Inkscape's also been able to output SVG files with "icc-color(...)" paint components[1] for several years now.		For Inkscape, "CMYK support" has been a frequent request by end users, needing some degree of color management for PDF export. Naively this might sound trivial - just add support for one more way to enter color values. Indeed, Inkscape already has a CMYK tab in the Fill and Stroke dialog for doing this. Inkscape's also been able to output SVG files with "icc-color(...)" paint components[1] for several years now.
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	As each of these areas draws from distinctly different programming skillsets, we'll divide the development steps into discrete projects organized along these lines.		As each of these areas draws from distinctly different programming skillsets, we'll divide the development steps into discrete projects organized along these lines.

	=== Add support to Cairo for exporting mesh shading to PDF ===		== Add support to Cairo for exporting mesh shading to PDF ==

	Cairo already supports rendering meshes to bitmaps, which we already use in Inkscape. But what's needed is an ability to export Type 6 (Coons patch) meshes to PDF/PostScript.		Cairo already supports rendering meshes to bitmaps, which we already use in Inkscape. But what's needed is an ability to export Type 6 (Coons patch) meshes to PDF/PostScript.
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	** One or more blog posts, or a patch to cairo-www		** One or more blog posts, or a patch to cairo-www

	=== Update Cairo to support PDF 1.6 ===		== Update Cairo to support PDF 1.6 ==

	Inkscape will need to support a variety of different print export formats.<br>		Inkscape will need to support a variety of different print export formats.<br>
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	* https://helpx.adobe.com/acrobat/using/pdf-conversion-settings.html#choose_an_adobe_pdf_preset_for_converting_files		* https://helpx.adobe.com/acrobat/using/pdf-conversion-settings.html#choose_an_adobe_pdf_preset_for_converting_files

	=== Add HDR image surface type to Cairo ===		== Add HDR image surface type to Cairo ==

	The new image format will implement the scRGB colorspace[2]. This involves writing code for Porter-Duff[3] compositing on the new format and making Cairo use them. Optionally, another (better but more involved) approach might be to extend the Pixman library to support the new format, and plumb in support for it in Cairo.		The new image format will implement the scRGB colorspace[2]. This involves writing code for Porter-Duff[3] compositing on the new format and making Cairo use them. Optionally, another (better but more involved) approach might be to extend the Pixman library to support the new format, and plumb in support for it in Cairo.
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	* [6]: "Fast Half Float Conversions" ftp://www.fox-toolkit.org/pub/fasthalffloatconversion.pdf		* [6]: "Fast Half Float Conversions" ftp://www.fox-toolkit.org/pub/fasthalffloatconversion.pdf

	=== Implement Color Management API for Cairo ===		== Implement Color Management API for Cairo ==

	In order for inkscape to produce CMYK Postscript and PDF files, Cairo needs support for other color spaces[1]. Cairo currently has several ways to accept color information (e.g. cairo_set_source_rgb), but we need a method to associate with Cairo surfaces that follows ICC standards and permits specification of input and output color formats, and a way to transform from input to output.		In order for inkscape to produce CMYK Postscript and PDF files, Cairo needs support for other color spaces[1]. Cairo currently has several ways to accept color information (e.g. cairo_set_source_rgb), but we need a method to associate with Cairo surfaces that follows ICC standards and permits specification of input and output color formats, and a way to transform from input to output.
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	* [8]: CSS Color Level 4: https://www.w3.org/TR/css-color-4/		* [8]: CSS Color Level 4: https://www.w3.org/TR/css-color-4/

	=== CMYK Color Profile Loading and Embedding GUI ===		== CMYK Color Profile Loading and Embedding GUI ==

	Printing companies will provide a color profile, such as "ISO Coated v2 300% (ECI)", that is provided as a file that the user will download and install to a directory on their system.		Printing companies will provide a color profile, such as "ISO Coated v2 300% (ECI)", that is provided as a file that the user will download and install to a directory on their system.
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	* [3]: http://www.freiefarbe.de/wp-content/uploads/2017/02/OCSC_20_GPL.zip		* [3]: http://www.freiefarbe.de/wp-content/uploads/2017/02/OCSC_20_GPL.zip

	=== Color Coding GUI ===		== Color Coding GUI ==

	This project implements a GUI that helps the user convert colors in a document to CMYK equivalents, spot colors, and CIELAB.		This project implements a GUI that helps the user convert colors in a document to CMYK equivalents, spot colors, and CIELAB.
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	* [1]: http://www.klaasnotfound.com/2016/06/05/creating-cmyk-prepress-pdfs-with-inkscape-and-scribus/		* [1]: http://www.klaasnotfound.com/2016/06/05/creating-cmyk-prepress-pdfs-with-inkscape-and-scribus/

	=== Support Cairo-based Color Management in Inkscape ===		== Support Cairo-based Color Management in Inkscape ==

	Once the color management API is landed in Cairo, implement internal support in Inkscape to make use of it.		Once the color management API is landed in Cairo, implement internal support in Inkscape to make use of it.
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	** Blog post, detailed email, or similar explaining the effects of these changes, as it relates to Inkscape development.		** Blog post, detailed email, or similar explaining the effects of these changes, as it relates to Inkscape development.

	=== Font Embedding for Print ===		== Font Embedding for Print ==

	Implement routines to perform several different types of adjustments to fonts used in an SVG document.		Implement routines to perform several different types of adjustments to fonts used in an SVG document.
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	** List potential issues to expect from odd fonts, and give some guidance on how they could be dealt with.		** List potential issues to expect from odd fonts, and give some guidance on how they could be dealt with.

	=== Prototype PDF Pre-Flight Checker Script ===		== Prototype PDF Pre-Flight Checker Script ==

	Write a command line tool that takes an Inkscape SVG document and performs a selected set of PDF standards checks on it.		Write a command line tool that takes an Inkscape SVG document and performs a selected set of PDF standards checks on it.
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	* [6]: https://www.prepressure.com/pdf/basics/preflight		* [6]: https://www.prepressure.com/pdf/basics/preflight

	=== Checker/Corrector C++ Core Code ===		== Checker/Corrector C++ Core Code ==

	Within the Inkscape codebase, implement the core classes and data structures for document checking, thus laying the core of Inkscape's future 'export for print services' capabilities. Similar code exists in Inkscape for style and attribute checking, and may be worth building upon - see Tavmjong for details.		Within the Inkscape codebase, implement the core classes and data structures for document checking, thus laying the core of Inkscape's future 'export for print services' capabilities. Similar code exists in Inkscape for style and attribute checking, and may be worth building upon - see Tavmjong for details.
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	** How to add new checks and corrections		** How to add new checks and corrections

	=== Pre-flight Checker GUI Dialog Mockup ===		== Pre-flight Checker GUI Dialog Mockup ==

	Design GUI dialogs for the pre-flight analysis.		Design GUI dialogs for the pre-flight analysis.
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	*** Explain what each widget in the GUI would do		*** Explain what each widget in the GUI would do

	=== Pre-flight Checker GUI ===		== Pre-flight Checker GUI ==

	The preflight GUI is accessed by the user when they are ready to do print production work.		The preflight GUI is accessed by the user when they are ready to do print production work.
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	** Speculative ideas on how a future implementation could do this even better, written as blog post(s), emails, or similar.		** Speculative ideas on how a future implementation could do this even better, written as blog post(s), emails, or similar.

	=== Export for Printing GUI ===		== Export for Printing GUI ==

	The process of finalizing a document to send for print is termed "Pre-Press". One of the substeps of this process is automated checks/corrections; this is termed "pre-flight" and addressed in some of the other proects. But there are additional steps beyond these which are manual or need more direct involvement from the user.		The process of finalizing a document to send for print is termed "Pre-Press". One of the substeps of this process is automated checks/corrections; this is termed "pre-flight" and addressed in some of the other proects. But there are additional steps beyond these which are manual or need more direct involvement from the user.
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	** Summary of the feature with pointers to docs and references		** Summary of the feature with pointers to docs and references

	=== Users Documentation ===		== Users Documentation ==

	This writing project is to create a useful and informative end-to-end guideline for creation of professionally printable PDF documents to Inkscape.		This writing project is to create a useful and informative end-to-end guideline for creation of professionally printable PDF documents to Inkscape.

Color Management Planning - Revision history

Moini: Fix heading levels

Tavmjong: /* Add support to Cairo for exporting mesh shading to PDF */

Tavmjong: /* Add support to Cairo for exporting mesh shading to PDF */

Moini: Add Bryce's CMYK / Color management project writeup with his permission.