Legacy ImageMagick Discussions Archive

I've compared two image with identify. One is exactly the same as the other (even the actual images are the same). The only difference is that one shows a histogram in identify and the other doesn't. How can I fix the one image so it's the exact same as the other (AKA: remove histogram from identify reports)?

Also, How can I replace "chromaticity" with "gamma"?

danegraphics wrote:I've compared two image with identify. One is exactly the same as the other (even the actual images are the same). The only difference is that one shows a histogram in identify and the other doesn't. How can I fix the one image so it's the exact same as the other (AKA: remove histogram from identify reports)?

One image is probably pseudocolor with a colormap and the other is probably truecolor.

It would help if you could post a link to your two images. You don't even say what type of images they are?

Also what version of IM and what platform.

danegraphics wrote:Also, How can I replace "chromaticity" with "gamma"?

You will have to explain this in much more detail? In the verbose information or in the image itself. Again you need to post a link to your image, so others can see what you are trying to do.

Gamma is an exponential setting and often is not associated with an image format. Chromaticity is a channel of certain types of images.

Gamma is usually used to adjust the luminosity/luminance/luma channal for overall brightness. Chromaticity has to do with color balance. See http://www.libpng.org/pub/png/book/chapter10.html

So you need to explain in more detail what you are really trying to do and why?

Just compare the "signature" from the "identify" report.

• identify -verbose image1 | grep ignature > image1.sig
  identify -verbose image2 | grep ignature > image2.sig
  cmp image1.sig image2.sig

(I omit the "s" because I can never remember whether
it's uppercase or lowercase).

see -define histogram:unique-colors=false
at http://www.imagemagick.org/Usage/files/#histogram

but I tried to add it to:

identify -define histogram:unique-colors=false -verbose image

and to

convert image -define histogram:unique-colors=false -verbose info:

but it did not turn off the listing of the histogram

danegraphics wrote:Also, How can I replace "chromaticity" with "gamma"?

You can't replace one with the other. They are two separate parts of color management.
It would be peculiar, and probably a mistake, if your image has chromaticity but not gamma
because gamma is the more important effect. If you are asking how to report gamma instead of
chromaticity, you're out of luck. Identify reports whatever features the image has.
Usually you'd expect to see just gamma, or gamma plus chromaticity, or just an iCCP
profile, or an iCCP profile plus gamma, or an iCCP profile plus gamma plus chromaticity.