How is an ICC profile embedded or built into an image?

Question

If I were to analyze or change an ICC profile embedded in an image, how should I proceed?

I'd also be glad to understand how an "end-user" is able to create these with a tristimulus colorimeter or a spectrophotometer and if/how this new profile can be added to a color capturing device (i.e. a camera).

My curiosity comes from images that were taken by a professional photographer. When I open them in GIMP, there's a pop-up referring "there is an embedded ICC profile" and if I "would like to convert the image to RGB (sRGB built-in)". I always convert all of them before using them, since the colors are slightly improved.

This is the image as it was provided by the photographer:

And this is after the embedded ICC profile was applied:

@joojaa This is great! They actually say: "lcms is a CMM engine; it implements fast transforms between ICC profiles". And by their trial of the professional solution, they provide a lot of options ("input for RGB, Gray, and CMYK spaces", "intents", "destination color space", etc.)... I never imagined that it could be so vast. — Armfoot, Aug 10 '15 at 16:07
The international color consortium defines 4 transformation intents for the colors that can not fit the gamut, read the tutorial. — joojaa, Aug 10 '15 at 16:08
@joojaa actually, in their own program they have a small description associated to all of the 7 types of "rendering intents" we can choose from when converting. — Armfoot, Aug 10 '15 at 16:13
hey allow for more intents and different white point/ blackpoint combinations. (adobe thus has 3*4 intents) — joojaa, Aug 10 '15 at 16:33
@joojaa I am impressed with the quantity of destination spaces they provide, for the conversions I tested there are shocking differences when ProPhotoRGB is used, [it's very hard to tell the differences when different intents are applied though], EDIT: in some situations intents are also very noticeable. — Armfoot, Aug 10 '15 at 16:44

score 2 · Answer 1 · edited Apr 13 '17 at 13:00

I realized that littlecms, suggested by joojaa in a comment above is very complete in dealing with the ICC profiles.

I did a few tests in their color translator program with different destination color spaces and the differences are great as you can see:

Original

sRGB-like

adobeRGB1998 (it seems it's the original color space)

appleRGB

And the most desirable results in my case are within the ProPhotoRGB color space:

linearProPhotoRGB

All of the above were following an automatic rendering intent but other intents bring slight variations (samples applied together with linearProPhotoRGB destination color space):

Absolute Colorimetric

Legacy Unadapted Absolute Colorimetric

I also realized that GIMP was actually restoring the original profile (not the opposite as I thought, i.e. instead of applying an embedded ICC profile, it was taking it off) and with this littlecms, now it does seem much simpler to "translate" color spaces than I thought.

How is an ICC profile embedded or built into an image?

1 Answers1