[BUGFIX] Re-apply colorspace to resulting image

When using filters the colorspace is not always applied.
A quickfix is to add the colorspace-setting again before
writing the output-image.
Multiple colorspace-settings on the commandline will be
executed in order. For example the grayscale-filter uses
"-colorspace GRAY". The final output-image can then be
converted to "-colorspace sRGB" again so the brightness
appears correct (not too dark) again.

Resolves: #78816
Releases: master, 8.7
Change-Id: I3fcabf8fdbb8d43f15662532b881501ebb43b1dd
Reviewed-on: https://review.typo3.org/50791


Reviewed-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Tested-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>