Problems converting CMYK to RGB with 6.9.11-19, regression?

[neekfenwick]

Description

I have a PHP app that converts a CMYK JPG to sRGB for display on the web. As far as I can see this worked up until the end of May. I believe the result would include an 'icc' profile on the image, 'identify -vebose' of the output image would include a "Profile-icc" under "Profiles". For example, the latest image being converted has a grey/white coloured appearance and has a CMYK colour profile. When converted to sRGB it ought to display the same grey/white appearance, but instead displays as a blueish tinge.

Now, 'identify -verbose' of the output image does not include an 'icc' profile, and viewing the image (on the web or via gnome Image Viewer) the colours appear wrong, the same as opening the original CMYK image.

I have a long description at https://stackoverflow.com/questions/62421778/why-would-converting-cmyk-image-to-srgb-for-display-on-web-work-locally-but-not

Steps to Reproduce

(taken from the SO post above)

    $master_img = new Imagick();
    $master_img->readImage($master_filename_abs);

    $icc_profile_contents = file_get_contents($icc_profile_file);
    $l->log('About to profileImage()...');
    $r = $master_img->profileImage('icc', $icc_profile_contents);
    $l->log("profileImage returned $r " . ($r == TRUE ? 'true' : 'false'));

    $space = $master_img->getImageColorspace();
    $l->log("Colorspace starts as $space, CMYK is " . Imagick::COLORSPACE_CMYK);
    $r = $master_img->transformImageColorspace(imagick::COLORSPACE_SRGB);
    $l->log("transformImageColorspace returned $r " . ($r == TRUE ? 'true' : 'false'));
    $space = $master_img->getImageColorspace();
    $l->log("Colorspace after conversion is $space, SRGB is " . Imagick::COLORSPACE_SRGB);

    $master_img->scaleImage(800, 0);
    $l->log('Saving RGB profile version to ' . $preview_filename_abs);
    $master_img->writeImage($preview_filename_abs);

System Configuration

CentOS 7.3 production system
ImageMagick 6.9.11-19 Q16 x86_64 2020-06-15
(ImageMagick from the remi repo)

• ImageMagick version: 6.9.11-19 (the latest available from remi repo)
• Environment (Operating system, version and so on): CentOS 7.3
• Additional information:
  I thought from the look of our yum logs that an upgrade from version 6.9.11.14-1 may have introduced the regression, however I have installed that old version (see https://forum.remirepo.net/viewtopic.php?pid=11207#p11207) and the colours still do not come out correctly.

Comparing 'identify -verbose' output for exactly the same image file produces different output with 6.9.11.14 and 6.9.11.19:

$ diff so_prod_6.9.11.14 so_prod
84,85d83
<   Profiles:
<     Profile-icc: 557168 bytes
89,90d86
<     icc:copyright: Copyright 2000 Adobe Systems, Inc.
<     icc:description: U.S. Web Coated (SWOP) v2
100,103c96,99
<   Pixels per second: 29.4645MB
<   User time: 0.020u
<   Elapsed time: 0:01.008
<   Version: ImageMagick 6.9.11-14 Q16 x86_64 2020-05-25 https://imagemagick.org
---
>   Pixels per second: 27.3785MB
>   User time: 0.010u
>   Elapsed time: 0:01.009
>   Version: ImageMagick 6.9.11-19 Q16 x86_64 2020-06-15 https://imagemagick.org

I don't see why the older 'identify' tool reports an icc profile, and the newer one does not, for the same JPG file (SO.jpg, attached here and also attached to the above mentioned Stack Overflow topic).

I am far from expert in this subject so I think adding any more attempts would muddy the water!

[neekfenwick]

Aside from my confusion with the PHP binding, which I still can't get to behave, I think I can show a problem with just the command line tools.

A little testing to demonstrate 6.9.11.14 vs 6.9.11.19, in each case I do the same conversions, 1/ just with -colorspace and 2/ with -profile and -colorspace:

Install 6.9.11.14:
$ convert src.jpg -colorspace srgb src_srgb_noprofile-6.9.11.14.jpg
$ convert src.jpg -profile AdobeRGB1998.icc -colorspace srgb src_srgb_withprofile-6.9.11.14.jpg

Install 6.9.11.19:
$ convert src.jpg -colorspace srgb src_srgb_noprofile-6.9.11.19.jpg
$ convert src.jpg-profile AdobeRGB1998.icc -colorspace srgb src_srgb_noprofile-6.9.11.19.jpg

Attached files:
Original src.jpg image..

Produced by 6.9.11.14 with just -colorspace:

Produced by 6.9.11.14 with -profile and -colorspace:

Produced by 6.9.11.19 with just -colorspace:

Produced by 6.9.11.19 with -profile and -colorspace:

This last one shows the only one that looks "right" with the grey/white colours is the one produced by 6.9.11.14. Both files produced by 6.9.11.19 show incorrect colours.

[urban-warrior]

Thanks for the problem report. We can reproduce it and will have a patch to fix it in the 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.

[neekfenwick]

I can confirm that building ImageMagick-6.9.11-22_beta20200623.tar.gz from source seems to show the issue as fixed.

$ ./configure --without-magick-plus-plus --with-jpeg --with-lcms
$ make -j4
$ ./utilities/convert src.jpg -profile AdobeRGB1998.icc -colorspace srgb src_srgb_withprofile_6.9.11-22.jpg

identify reports the image has an icc profile and it displays well in nautilus. Thank you!

[dlemstra]

And thank you for reporting this 👍