46 lines
2.2 KiB
Markdown
46 lines
2.2 KiB
Markdown
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== img2pdf ==
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Lossless conversion of images to PDF without unnecessarily re-encoding JPEG
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files. Thus, no loss of quality and no unnecessary large output file.
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PDF is able to embed JPEG images as they are without re-encoding them (and
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hence loosing quality) but I was missing a tool to do this automatically, thus
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I wrote this piece of python code.
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If you know how to embed JPEG images into a PDF container without
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recompression, using existing tools, please contact me so that I can put this
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code into the garbage bin :D
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The program will take image filenames from commandline arguments and output a
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PDF file with them embedded into it. If the input image is a JPEG file, it will
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be included as-is without any processing. If it is in any other format, the
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image will be included as zip-encoded RGB. As a result, this tool will be able
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to lossless wrap any image into a PDF container while performing better (in
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terms of quality/filesize ratio) than existing tools in case the input image is
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a JPEG.
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For the record, the imagemagick command to lossless convert any image to
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PDF using zip-encoding, is:
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convert input.jpg -compress Zip output.pdf
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The downside is, that using imagemagick like this will make the resulting PDF
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files a few times bigger than the input JPEG and can also not output a
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multipage PDF.
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img2pdf is able to output a PDF with multiple pages if more than one input
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image is given, losslessly embed JPEGs into a PDF container without adding more
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overhead than the PDF structure itself and will save all other graphics formats
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using lossless zip-compression.
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If you find a JPEG that, when embedded can not be read by the Adobe Acrobat
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Reader, please contact me.
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For lossless conversion of other formats than JPEG, zip/flate encoding is used.
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This choice is based on a number of tests I did on images. I converted them
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into PDF using imagemagick and all compressions it has to offer and then
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compared the output size of the lossless variants. In all my tests, zip/flate
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encoding performed best. You can verify my findings using the test_comp.sh
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script with any input image given as a commandline argument. If you find an
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input file that is outperformed by another lossless compression, contact me.
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