Hi Steve,

Steve Stavropoulos wrote:

Whatever you do, you will have to make a compromise. The question is,

There we are in full agreement :)

You are worried about quantization errors during the conversion, but if you do the conversion in 16 bit or more I think you will not have much problems. In the littlecms site I found a command line program that does the colorspace conversion with very high accuracy. Check

I'm not worried about the conversion so much as the fact that the limited precision of the destination data (8-bit RGB) will cause us to lose colour information. A conversion of 8-bit data between two RGB profiles will not be a 1:1 mapping, so the converted data will not use the full dynamic range that 8-bit RGB can provide. Since the dynamic range of 8-bit RGB is already severly limited, I consider impairing it further to be unacceptable.

The bigger problem we will have when converting colorspaces, is the
limited gamut of sRGB in comparison with the source colorspace. For
example, if we convert from CMYK to sRGB, then almost any color with CMYK
values in the range C>90, M<10, Y<10, will have no sRGB counterpart. Would
it be feasible to switch from sRGB to something better? Maybe AdobeRGB? I found usefull the
http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html when comparing color spaces.

If the GIMP is going to hand off the colour-matching work to littlecms, then using a different profile is as trivial as providing the filename of AdobeRGB instead of sRGB!

Keep in mind though, that if we change the internal color space from sRGB
to something else there must be an option for the user to save his image
in sRGB (and maybe that should be the default on many cases). sRGB is the best option when someone tries to view an image in a computer monitor with no color profiling.

Absolutely - though under my proposal, if an sRGB image is loaded, then for that image sRGB *is* the working space.

As for the proposed conversion on save to the starting colorspace, I completely dissagree. I don't see any reason to introduce more errors coming from a less than optimal conversion.

Agreed. Subconsciously, I suppose I'd considered it "good manners" to save a modified image in the same colour space it started in, but you're right, this is not necessary.

All the best
Alastair M. Robinson

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