Re: Panther, sRGB, web browsers
Re: Panther, sRGB, web browsers
- Subject: Re: Panther, sRGB, web browsers
- From: John Fieber <email@hidden>
- Date: Thu, 18 Dec 2003 15:55:43 -0500
On Dec 15, 2003, at 5:59 PM, Chris Murphy wrote:
On Dec 15, 2003, at 12:37 PM, John Fieber wrote:
Okay, I'm now puzzled by this. In "ColorSync on Mac OS X"
(http://developer.apple.com/technotes/tn/tn2035.html) under the
heading "ColorSync Changes for Mac OS 10.2"
Profile Changes when Printing or Displaying Untagged Data
PDF Display
On Mac OS 10.2, untagged RGB data in PDF will be tagged with the
Generic RGB profile, and as a result it will be color-matched to the
screen.
This isn't how it works in Panther's Preview or Mail applications. I
have an RGB test file, which is a PDF, with specific RGB values
(solids), and digital color meter shows those values that are in the
file. If I make a copy of this image, assign Generic RGB, embed and
save, then hand it over to Preview or Mail the numeric values differ
from what's in the file. So I conclude in the first case that untagged
documents, including PDF, assume monitor RGB in Panther, not Generic
RGB, nor per the message in the ColorSync Utility>Preferences window.
I'm not sure I follow the methodology. I'm not sure how the color
meter works and even less sure of the situations where it even should
match the values stored in the file. But my an independent methodology
I've verified that it sure seems to be the display profile that is
used.
I just took a raster RGB file with some color patches and saved three
versions: tagged with Generic RGB, tagged with the display profile and
untagged. Same RGB numbers in all three. Preview renders the
no-profile case the same as the tagged-with-display profile case.
Same behavior with Safari, TextEdit and OmniGraffle (a rare no-adobe
third party application that seems to properly handle ICC tagged images
both for display and printing.) Applications, such as Netscape and
QuickTime Player, that don't attempt to read and use profiles render
the same colors as the color managed applications render the
tagged-with-display case. From this sampling of applications I
conclude that IF it is true that untagged data is assumed to be Generic
RGB, then the higher level APIs (Cocoa NSImage, QuickTime, QuickDraw,
etc.) must be overriding that by tagging the data with the display
profile by the time it gets to Quartz rendering.
In the face of untagged data, you can only guess what to do to bring it
into a color managed universe (and MacOS X claims to be a color managed
universe). The choice of Generic RGB (or sRGB or MyFunkyRGB) is
rather arbitrary, but it really seems a at least somewhat less
arbitrary than the display profile. And since nobody seems to have
found an actually useful function for the "default profile" colorsync
settings, maybe they should just disappear so as to avoid confusing
people?
Can we look forward to a New and Improved version of the ColorSync on
MacOS X document in the future to clarify some of this? Or is the
current implementation state just as confusing as it seems such that
more documentation would just reaffirm the confusion?
-john
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| References: | |
| | >Panther, sRGB, web browsers (From: Chris Murphy <email@hidden>) |
| | >Re: Panther, sRGB, web browsers (From: Steve Upton <email@hidden>) |
| | >Re: Panther, sRGB, web browsers (From: Chris Murphy <email@hidden>) |
| | >Re: Panther, sRGB, web browsers (From: John Gnaegy <email@hidden>) |
| | >Re: Panther, sRGB, web browsers (From: John Fieber <email@hidden>) |
| | >Re: Panther, sRGB, web browsers (From: Chris Murphy <email@hidden>) |