Can a GIF have a CMYK profile?

Question

While working on an InDesign script that checks the links used in a file I decided to check what color profile has been used on images so I can output it to a log for the user however when I write my conditional to check if a link is a GIF I was unsure if a GIF could actually have a CMYK profile. When I research wikipedia:

The format supports up to 8 bits per pixel for each image, allowing a single image to reference its own palette of up to 256 different colors chosen from the 24-bit RGB color space. It also supports animations and allows a separate palette of up to 256 colors for each frame. These palette limitations make the GIF format less suitable for reproducing color photographs and other images with continuous color, but it is well-suited for simpler images such as graphics or logos with solid areas of color.

It mentions RGB only but it doesn't mention if a CMYK profile can be supported. So, can a GIF support a CMYK profile?

Answer 1

There is no mention of CMYK in the GIF specification, and it only supports color triplets. Take a peek at the syntax for color tables given by the spec:

      7 6 5 4 3 2 1 0        Field Name                    Type
     +===============+
  0  |               |       Red 0                         Byte
     +-             -+
  1  |               |       Green 0                       Byte
     +-             -+
  2  |               |       Blue 0                        Byte
     +-             -+
  3  |               |       Red 1                         Byte
     +-             -+
     |               |       Green 1                       Byte
     +-             -+
 up  |               |
     +-   . . . .   -+       ...
 to  |               |
     +-             -+
     |               |       Green 255                     Byte
     +-             -+
767  |               |       Blue 255                      Byte
     +===============+

Since CMYK values would require color quadruplets, any parser that follows the spec wouldn't know what to do with a "CMYK GIF" even if you shoehorned the values in.

Answer 2

The short answer is no, a GIF can't support a CMYK profile.

A CMYK profile is a series off curves that map the percentage value of each separation to a target. GIF images are saved as INDEXED COLOUR, which then references an RGB value for each colour. While CMYK values could be derived from the RGB values (the RGB gamut is wider than the CMYK gamut so some colours would have to be approximated), there would not be a continuous, complete 'curve' of colour values so the profile would not have the necessary freedom to adjust.

If you are supplied with GIFs or RGB files or anything other than CMYK for print work then the best route is to convert them to CMYK and issue a proof for approval. Sometimes all will be well, sometimes it will be a disaster.

Also, I take issue with the suggestion that the 'correct' pronunciation is with a soft g (as in sounds like JIF), the G in GIF stands for Graphic, with a hard G, so GIF should be pronounced with a G that sounds like the G in Graphic. I don't care what anybody (including the inventors of the format) say.