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I have a TIFF image and a JPG image. http://regex.info/exif.cgi says that they both use a CMYK color space labelled as "SWOP (Coated), 20%". How do I accurately and losslessly convert the TIFF image into an sRGB PNG and the JPG image into an sRGB JPG?

Hiccup
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1 Answers1

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It's unlikely you will be able to do this losslessly if for no other reason than CMYK covers a different (but overlapping) color space than sRGB. Additionally, there are several algorithms for converting between the two color spaces, each of which produces slightly different results.

From Understanding Color:

Graphs of the color spaces for CMYK, sRGB, and AppleRGB

Converting the TIFF to PNG along with the color space may be done relatively losslessly. As you can see from the graph, blue-greens and bright yellows may be a problem when converting from CMYK to sRGB.

Converting the color space on a JPG will be lossy since changing the colors necessarily changes the compression due to the nature of JPEG compression.

Adobe has these instructions for doing color space changes in Photoshop:

  1. Choose Edit > Convert To Profile.
  2. Under Destination Space, choose the color profile to which you want to convert the document’s colors. The document will be converted to and tagged with this new profile.
  3. Under Conversion Options, specify a color management engine, a rendering intent, and black point and dither options (if available). (See Color conversion options.)
  4. To flatten all layers of the document onto a single layer upon conversion, select Flatten Image.
  5. To preview the effects of the conversion in the document, select Preview.

Adobe Illustrator, InDesign, and Lightroom can also do color space conversions.

Ouroborus
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