[Openicc] PDF and rendering intents

[Leonard Rosenthol]

[sorry the delay in answering – been busy with a few other things]

PDF provides for the specification of a single Rendering Intents as part of the graphics state of any object.  They are required to be processed as part of the “conversion of CIE-based colours to device colours”.   The default value is RelativeColorimetric.

That said, it is true that some RIPs offer controls that let users screw with that handling (in various ways).   Doing so MAY bring the processing OUT OF COMPLIANCE with the standard (depends on what the exact change is) but that’s what users apparently want :(.

Also, as Ann said, the current spec doesn’t enable v4 profile functionality for separate input & output intents. That is something I need to get addressed for ISO 32000-2.

Hope that helps.

Leonard

From: Ann McCarthy [mailto:almccart at lexmark.com]
Sent: Monday, May 16, 2011 10:31 AM
To: Open ICC Color Managment
Cc: Leonard Rosenthol
Subject: Re: [Openicc] PDF and rendering intents

Rendering intent handling is a weak area in current PDF cm.  This might be why you see print systems ignoring or overriding the info in the file.

Leonard has agreed to work on upgrading next gen PDF std so that rendering intent will be specified for output profile separate from input profile. This is part of what is needed. Specific RI for each source content object and a separate RI for the output profile.

Think about it.

Rendering intent is essentially a transform selector.

Input profiles and output profiles each have multiple transforms available.

Certain workflow scenarios REQUIRE that the rendering intent for the input profile (source profile) not be == to the rendering intent for the output profile (destination profile).

In general, rendering intent selectors apply to one color transform operation. Once applied, the same selectors should often NOT be used in the next cm transform in a multi-stage color transform workflow.  So -- more smarts are needed around when/what RI to use. This really becomes an area where a workflow system must apply smarts to determine what is appropriate in the context of the workflow use cases.


Best regards,
Ann L McCarthy
Imaging Systems R&D
Lexmark International, Inc.


On Fri, May 13, 2011 at 10:12 PM, Chris Murphy <lists at colorremedies.com<mailto:lists at colorremedies.com>> wrote:
I am wondering from anyone, but most likely Leonard, what the various PDF specs require in terms of rendering intent handling. I know the rendering intent can be set in the PDF itself but the questions are:

1. What is Default? For example InDesign has a Default rendering intent option per object, but what is the default? Does this mean "defer to RIP's settings?" Or the application default for that object type? Or is there a default intent in a spec somewhere?

2. Are RIPs required to honor the intent setting in the PDFs, or are they just suggestions? Or is it context specific? (Suggestion for PDF, but required for PDF/X?)

I ask because I see many RIPs that support PDF documents apply their own rendering intent settings but the UI makes it ambiguous whether the RIP settings override the PDF, or the PDF object intent overrides the RIP, but in practice it appears the RIP settings always have an affect.


Chris Murphy
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