gs-output-test.txt

Checking ghostscript output
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To easily view the difference between two images, you can use the composite tool from Image Magick (http://www.imagemagick.org).

composite <ref bmp> <target bmp> -compose Difference diff.bmp

For files that are not in bmp format, use ghostscript convert them to BMP first e.g. 
For CMYK, since this is not an encapsulated format, you need to supply the width and height.
gswin32c -dBITS=<N> -dSCALE=1 -sDEVICE=bmp256 -sOutputFile=target.bmp -dUseCIEColor -- viewcmyk.ps <filename> <width>
e.g.
$ /c/apps/gs/gs8.53/bin/gswin32c.exe -dBITS=2 -dSCALE=1 -sDEVICE=bmp256 -sOutputFile=test.bmp -dUseCIEColor -- viewcmyk.ps gs8.banner.cmyk2b 612

The output image should be mostly empty (black). Any visible pixel reflects the difference between the output image and the reference image.
Reference output can be found under oav2/gs-output.