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tiffcolor-profile
Harald K
Harald K

Reputation: 27084

How to deal with TIFF files with incompatible ICC color profiles

I'm writing a TIFFImageReader plugin for Java (ImageIO), but the question is generic:

What is the "correct" way to deal with a TIFF file that contains an ICC color profile that does not match the image data (ie. image data is RGB, but TIFF metadata contains a CMYK ICC profile)?

I recently had a user report this problem. The quick and easy fix is to just issue a warning, and ignore the color profile. However, the TIFF 6.0 specification doesn't mention ICC profiles at all, or how to deal with them. ICC Specification ICC.1:2010-12, annex B does describe how to correctly embed color profiles, but does not mention profile relation to image data (other than being in the same IFD).

Upvotes: 0

Views: 1816

Answers (1)

Mark
Mark

Reputation: 92440

There is no "correct" way to deal with this as a general problem.

The color profile tells you how to connect RGB numbers, which by themselves are just abstract values, to a device-independent space like CIE XYZ or CIELAB so you can correctly interpret them as colors and display them in a consistent way.

With an incorrect profile (or without a profile for that matter) you can't know how to interpret the RGB numbers. It's a little like getting a weight measurement without units of with incorrect units. If I have a recipe that calls for 5 units of water, and you don't know whether that should be 5 grams or 5 cups, you are kind of stuck. You can either guess or tell the user their information doesn't make sense.

In many cases you can make an educated guess based on domain-specific information. For example, we can often correctly guess that images on the web without a profile will likely be sRGB data, but that's just a guess. A lot like assuming a recipe for cookies that calls for 1 flour probably means 1 cup of flour.

It's very unusual for an RGB image to carry a CMYK profile — it's really hard to understand how that even happens. If I had to deal with this, I would throw an error with a message about the problem. If color accuracy is not critical, you could also strip the profile and let whatever downstream process needs to display the image deal with the untagged image, or guess something reasonable like sRGB with the understanding that it is just a guess.

Upvotes: 1

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