-clone converts grayscale image to sRGB

[datro]

Please see the following thread for all the details:

viewtopic.php?f=1&t=33440

[datro]

For anyone following this bug:
There have been a number of additional updates to the linked thread above which include important new information.

[magick]

We require a minimal command line to reproduce the problem before we will investigate further. These commands prove -clone does not affect the image colorspace:

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convert logo: logo.pgm
convert logo.pgm -clone 0 -delete 0 logo.mpc
identify -verbose logo.mpc
head logo.mpc
...
type=Grayscale
colorspace=Gray
...

What are the fewest command-line options you can come up with that illustrates the problem you are having. We will investigate further once we see what you come up with.

[datro]

OK, try this (IM 7.0.7-22 Q16 HDRI) on Windows 10:

This fails:

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magick input.tif -write input.icc ^
-profile Gray-elle-V2-g10.icc -distort Resize 500 ^
( -clone 0 -gamma 3 -gamma 0.33333 ) ( -clone 0 ) -delete 0  ( -clone 1 ) -compose over -composite ^
-profile input.icc output.tif

Result:

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magick: color profile operates on another colorspace `icc' @ error/profile.c/ProfileImage/1018.

This is as simple as I can make it. As explained in my last post of the above referenced thread, the problem is not with clone per se, but with how the resize and the first clone (with the gamma conversion) in the sequence above interact.

If you take out the resize, it works:

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magick input.tif -write input.icc ^
-profile Gray-elle-V2-g10.icc ^
( -clone 0 -gamma 3 -gamma 0.33333 ) ( -clone 0 ) -delete 0  ( -clone 1 ) -compose over -composite ^
-profile input.icc output.tif

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magick identify output.tif
output.tif TIFF 600x761 600x761+0+0 16-bit Grayscale Gray 942600B 0.000u 0:00.000

"input.tif" and "Gray-elle-V2-g10.icc" can be obtained here for testing:
https://www.dropbox.com/sh/svxba869nhqa ... lD-za?dl=0

(Edit: Fixed dropbox link)

Hope this helps.

[fmw42]

I have some further simpler tests that show it is related to adding -evaluate pow 0.5 in combination with -distort Resize, but works using -evaluate pow 2

This works in IM 7 -- no -evaluate pow 0.5

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magick input.tif -write input.icc \
-profile Gray-elle-V2-g10.icc -distort Resize 500 \
\( -clone 0  \) -compose over -composite \
-profile input.icc output.tif

This fails in IM 7 -- with -evaluate pow 0.5

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magick input.tif -write input.icc \
-profile Gray-elle-V2-g10.icc -distort Resize 500 \
\( -clone 0 -evaluate pow 0.5  \) -compose over -composite \
-profile input.icc output.tif

This works in IM 7 -- with -evaluate pow 2

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im7 magick input.tif -write input.icc \
-profile Gray-elle-V2-g10.icc -distort Resize 500 \
\( -clone 0 -evaluate pow 2  \) -compose over -composite \
-profile input.icc output.tif

This works in IM 6 -- with -evaluate pow 0.5

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convert input.tif -write input.icc \
-profile Gray-elle-V2-g10.icc -distort Resize 500 \
\( -clone 0 -evaluate pow 0.5  \) -compose over -composite \
-profile input.icc output.tif

It also works if one takes out the -distort Resize but keep the -evaluate pow 0.5

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magick input.tif -write input.icc \
-profile Gray-elle-V2-g10.icc \
\( -clone 0 -evaluate pow 0.5  \) -compose over -composite \
-profile input.icc output.tif

[magick]

Thanks for the problem report. We can reproduce it and will have a patch to fix it in GIT master branch @ https://github.com/ImageMagick/ImageMagick later today. The patch will be available in the beta releases of ImageMagick @ https://www.imagemagick.org/download/beta/ by sometime tomorrow.