Gamma correct a PS file

in Genius Bar edited January 2014
I have a postscript file on my UNIX box that I need to print. Of course the gamma of the printer is an issue. The grayscale images come out dark.

How would I go about gamma correcting the postscript file? There's got to be some way to do it using acrobat to convert it to pdf? Maybe something else?


  • Reply 1 of 5
    Nobody knows?
  • Reply 2 of 5
    I'm not aware of a method to do it without using an image editor like photoshop or graphic converter. (I've got Acrobat 4 which has horrible color management; don't know what Acrobat 5 has.)

    I'm assuming that the ps file you have started off as something like a jpeg or tiff file. I'm also assuming that you have a single image, not something like a book which has been output as postscript. If photoshop can't open the ps file directly, try distilling it into a pdf first then bringing it into photoshop. Any vector objects in the file (fonts, line art) will rasterize when you do it this way, so be sure to tell photoshop to raster it as the size and resolution you want to use it at.

    If the file started off as an illustrator or freehand file, try opening and adujusting it in one of those progams first (to preserve the vector info) before bringing it into photoshop.

    Now if you do have a long doc (a book, pamphlet, or something other than a single image on a single page) that you want to color correct globally...well, the only way I can see to do it would be to go back to the original document, color correct the original images used, and re-output the postscript file. Unless, of course, you know how to code postscript or have access to a commercial RIP, and even then I'm not sure if you'd be able to make any adjustments that wouldn't affect the entire file (text and all), and not just the images. At least, not easily...

    Good luck!
  • Reply 3 of 5
    There's way too many images in it and many are in eps files. So I'd have to go back and redo the images within each eps file. Not fun.
  • Reply 4 of 5
    I found on the google news groups archive how to do this. You add this line to the top of your postscript file.

    [code]{0.5 exp} dup dup currenttransfer setcolortransfer</pre><hr></blockquote>

    You can change use 0.5 or 0.33 or 0.75 depending on how much you want to correct. Right now my printer seems to be ignoring this chance. Ghostscrip and the PDF Distiler have no trouble though?
  • Reply 5 of 5
    Follow up.

    I had to use ghostscript to rip the PS file to a raw format for the printer and then pipe that over the raw print que. It worked though.
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