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When combining images quality is lower

Aug 5, 2013 2:22 AM

Tags: #text_recognition #combine_images #output_quality

Often I create PDF's from screencaptures.


In case of a series of sequential screencaptures I wish to use the combine files to PDF (context menu option).


On the other hand, in cases of single screenshots, or just a very few, I use the create PDF from Clipboard.


It strikes me that the quality of the resulting 'binder1.pdf' is slightly lower than those ones created using the Clipboard option.


Acrobat-Combining vs Clipboard-quality-05082013 100520.jpg


This may have some effects on text recognition.


Above are both 200% zoom, hopefully it shows the difference.


Can this be avoided with some preference.

Note: I donot mind the size of the file, for me the best quality counts.





oh, btw, under binder options file size is set to large. makes no difference.

SnagIt-05082013 111949.jpg

  • Currently Being Moderated
    Aug 5, 2013 7:15 AM   in reply to adwul62

    If you would set your screen capture app to use PNG or Tiff instead of JPEG you would avoid this.

    This is a result of the compression used for JPEG files. JPEG is a Lossy Format and each time its compressed and re-saved you get this.


    Even just the act of opening to a view a JPEG decompresses the file and when quit recompresses the file. Each time it is recompressed detail is lost.


    Once or twice there is little perceptible effect. but after 8-10 times the effect begins to happen.


    When I see a File that looks like your second example Ican tell its JPEG file without even looking at the extension

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  • Currently Being Moderated
    Aug 5, 2013 8:01 AM   in reply to adwul62

    Looks as if Acrobat is using JPEG compression itself (though not quite as badly).


    First thing to check.


    If you take just one of these PNG files and use Create PDF from file (not From Multiple Files), do you see the same effect? If so, go back into create from file and click Settings. For Color be sure to use ZIP.

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  • Currently Being Moderated
    Aug 5, 2013 8:24 AM   in reply to adwul62

    Be sure to choose FIles of type: PNG specifically.

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  • Currently Being Moderated
    Aug 5, 2013 8:35 AM   in reply to adwul62

    No, choose ZIP. If you can't afford the size of file that results, look at highest quality JPEG, yes, but on no account to this if you plan to OCR.

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  • Currently Being Moderated
    Aug 5, 2013 8:38 AM   in reply to Test Screen Name

    More... set the Grayscale settings too if your scans are not colour (they might appear as greyscale or colour in PNG).


    More...if you are NOT doing OCR, but scanning for screen viewing and printing, 200 dpi is probably plenty; more would be extravant on disk space. Scanning at monochrome will make by far the smallest but you might want a higher resolution. Carry on with the experiments, it's always worth doing a random selection of originals before committing to a big pile of paper.

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