Comparing Adobe Acrobat vs. Ghostscript ATS Compare

To compare rendering created by Adobe Acrobat with Ghostscript the following process was performed:

• The ATS files were transformed from their current state to a PDF format that forced the embedding of the fonts.
• Adobe Acrobat DC was used to generate a 300dpi SWOP CMYK TIFF file for each PDF page.
• Ghostscript was used to also generate a 300dpi SWOP CMYK TIFF files for each PDF page.
• Since Acrobat SWOP CMYK TIFF format does not support overprint, Ghostscript TIFF files were generated with oveprint turned off.
• The resulting Ghostscript and Acrobat generated TIFF files were compared using bmpcmp -w5 -l -t33 which does a comparison with a 5x5 window in CIELAB delta E color space with the a delta E threshold of sqrt(33).
• The resulting output from bmpcmp was transformed to a form that was suitable for web viewing (thanks Robin!).
• The results are available at http://peeved.ghostscript.com/mvrhel/bmpout/compare.html
• At the top of the page and the bottom of the page, you can see a navigation bar to each web page (463 pages).
• There is also a Next>> link at the top and bottom right handside that will navigate you to the next page.
• When viewing you will see that each PDF page is broken into smaller parts to allow easier viewing.
• Each set of three is (from left to right) the Acrobat output, Ghostscript output, a difference file.
• The difference file shows a colorful encoding of black, green and red.
• Black regions are no different, green regions have small differences and red regions have large differences.
• At the top of each PDF page section you will see a link like 5: tests_private/pdf/PDF_1.7_ATS_2013/TestFiles/AC9Z61EC_A-1B.pdf
• This hyperlink would take you to the actual PDF file that was used to generate the TIFF files
• The page number of the PDF file for a particular image is shown at the bottom of the image. For example Page=01 PageSize=2550x3300 TopLeft=(1879,59) W=512 H=901 XY
• Note that each page has a simple html address. For example page 10 is compare10.html

To do:

• Review each page.
• For pages that have red content make a note of

1. The html page (e.g. compare10.html)
2. Reference number of the image (e.g. item 5 for 5: tests_private/pdf/PDF_1.7_ATS_2013/TestFiles/AC9Z61EC_A-1B.pdf)
3. Make a visual comparison. Do you see a difference in those red regions?
4. Click on the link associated with the file, open in Acrobat and navigate to the page. Do you notice any differences?
5. What appears to be the difference? Is there missing content, extra content, item in wrong place, is the color wrong?

As an example, go to http://peeved.ghostscript.com/mvrhel/bmpout/compare2.html and scroll down to item 53. Note that there is s difference. The issue is that the text in Acrobat is bolder than the text in Ghostscript.

Another example is http://peeved.ghostscript.com/mvrhel/bmpout/compare3.html. Scroll to item 77. Note that there is a color difference in the images. The AR image is lighter and has a different hue than the Ghostscript rendering.

Both of these should show up in a written list with consistent usage so that we can readily see the most common problems. If you can put in the links that would be great. For example:

http://peeved.ghostscript.com/mvrhel/bmpout/compare2.html , item 53, Acrobat text bolder than ghostscript text

http://peeved.ghostscript.com/mvrhel/bmpout/compare3.html, item 77, color difference in images

We can then readily navigate and do a deeper assement of any issues.

-- Michael Vrhel - 2020-07-06

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