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  • Odd results from GhostScript

    From Rob Hemmings (News)@21:1/5 to All on Wed Jun 10 14:50:20 2020
    I've been playing with GhostScript (version 9.26) on RISC OS as I was
    intending to write a RISC OS front end to calculate printing costs and I
    need to use GhostScript to give an estimation of the amount of each
    colour of ink needed to print a (pdf) file. However, I'm getting some
    strange results and would appreciate any ideas or suggestions.

    I'm using the GhostScript device of ink_cov to do the calculation. An
    actual command line that demonstrates the issue is:

    gs -o - -sDEVICE=ink_cov inputfile

    (where I replace "inputfile" with the name of the file I am trying to
    analyse)

    I'm using version 9.2 of GhostScript on Windows and that is producing consistent results with any type of pdf file. On RISC OS I get a
    believable result if I use a pdf file that has been created on Windows
    with colour in CMYK format although a little oddly the results are
    slightly different from those produced on Windows with the same file
    which I would have expected to be the same.

    However, much more of a problem on RISC OS is that with a pdf file that
    has not been created in CMYK colour it reports exactly the same
    (incorrect) figure for each ink instead of giving the correct
    proportions. Running GhostScript on the same file on Windows gives a
    correct result with the usage of each ink being different. Can anyone
    suggest what might be going on?

    --
    -------------------------------------------------------------
    Rob Hemmings Southport

    [email protected]

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  • From Theo@21:1/5 to [email protected] on Wed Jun 10 17:57:11 2020
    "Rob Hemmings (News)" <[email protected]> wrote:
    I'm using version 9.2 of GhostScript on Windows and that is producing consistent results with any type of pdf file. On RISC OS I get a
    believable result if I use a pdf file that has been created on Windows
    with colour in CMYK format although a little oddly the results are
    slightly different from those produced on Windows with the same file
    which I would have expected to be the same.

    However, much more of a problem on RISC OS is that with a pdf file that
    has not been created in CMYK colour it reports exactly the same
    (incorrect) figure for each ink instead of giving the correct
    proportions. Running GhostScript on the same file on Windows gives a
    correct result with the usage of each ink being different. Can anyone suggest what might be going on?


    How strange. It appears there are two devices, 'ink_cov' and 'inkcov' which follow different code paths: https://github.com/ArtifexSoftware/ghostpdl/blob/master/devices/gdevicov.c
    Are you sure you're using the same one?
    Also, are you sure the DPI is the same (default is 75 dpi) and not getting
    set by some config file maybe?

    Otherwise I'm wondering if there's some undefined behaviour in there
    somewhere, but I can't see anything obvious...

    Theo

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Rob Hemmings (News)@21:1/5 to Theo on Wed Jun 10 19:04:31 2020
    In article <l9u*[email protected]>,
    Theo <[email protected]> wrote:
    "Rob Hemmings (News)" <[email protected]> wrote:
    I'm using version 9.2 of GhostScript on Windows and that is producing consistent results with any type of pdf file. On RISC OS I get a believable result if I use a pdf file that has been created on Windows
    with colour in CMYK format although a little oddly the results are
    slightly different from those produced on Windows with the same file
    which I would have expected to be the same.

    However, much more of a problem on RISC OS is that with a pdf file
    that has not been created in CMYK colour it reports exactly the same (incorrect) figure for each ink instead of giving the correct
    proportions. Running GhostScript on the same file on Windows gives a correct result with the usage of each ink being different. Can
    anyone suggest what might be going on?


    How strange. It appears there are two devices, 'ink_cov' and 'inkcov'
    which follow different code paths: https://github.com/ArtifexSoftware/ghostpdl/blob/master/devices/gdevicov.c Are you sure you're using the same one? Also, are you sure the DPI is
    the same (default is 75 dpi) and not getting set by some config file
    maybe?

    Otherwise I'm wondering if there's some undefined behaviour in there somewhere, but I can't see anything obvious...

    Theo

    Hi Theo, thanks for the thoughts. I'm definitely using ink_cov as inkcov
    does not report on ink usage but on which areas of the page include an
    ink (i.e. it takes no notice of density). That confused me quite a bit
    to begin with as the documentation for them is fairly thin.

    I hadn't thought about DPI but as far as I know I've done nothing to
    affect that as I've just tried running exactly the same command on the
    same file on both platforms, admittedly with a slightly different version number of GhostScript. I suppose it is possible that could affect the
    first issue I've mentioned above. However, I don't see how altering DPI
    surely could not make all ink coverage values the same when they are
    clearly not if you look at the document.

    --
    -------------------------------------------------------------
    Rob Hemmings Southport

    [email protected]

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)