TYPO3 Core

Hi folks,

I wrote a quick&dirty "workarround" - or better a proof of concept - for the cmyk images handling, look at thumbs.php, line 238:
$parameters = '-sample '.$this->size.' '.$colors.' '.$this->wrapFileName($this->input.'[0]').' '.$this->wrapFileName($this->output);

1. AST Begin: "Patch" imageMagickCommand(): Add profile option if a cmyk image is detected!
   // 1. Get colorspace from image: Tested CMYK images return "type: color separated" under T3 4.1.5 & IM 4.2.9
   $cmd = t3lib_div::imageMagickCommand('identify', '-verbose '.$this->wrapFileName($this->input.'[0]'));
   $arrImg = array();
   exec($cmd, $arrImg);
   // 2. If CMYK is detected, add profil option
   if (trim($arrImg²) == 'type: color separated') {
   $profileCMYK = $TYPO3_CONF_VARS['GFX']['im_path'].'USWebCoatedSWOP.icc';
   $profileRGB = $TYPO3_CONF_VARS['GFX']['im_path'].'ColorMatchRGB.icc';
   $parameters .= ' -profile '.$profileCMYK.' -profile '.$profileRGB;
   }
2. AST End

If you can see, adding profiles solves the problem! But therefore you have to put the needed ICC profiles on your server ... Profiles are aviable under:
http://www.adobe.com/support/downloads/detail.jsp?ftpID=3680

It seems, that there is a problem with the identify -verbose command! If you can bring in a better cmyk detection routine, just feel free!

So, let's discuss and improve the code! ;)

The Adobe profiles you mention do not have a GPL compatible license, so we can not distribute them in TYPO3. There are profiles available at eci.org, but from reports on the web I understand that using profiles only improves the colour rendering slightly.
It seems that adding -colorspace rgb or -colorspace sRGB will at least convert CMYK to RGB. If this has no visible influence on RGB images and produces acceptable results for CMYK images it might be a simple solution.

for CMYK images do you mean for example a .tiff file saved with CMYK color space?