forked from josch/img2pdf
56 lines
2.4 KiB
Markdown
56 lines
2.4 KiB
Markdown
img2pdf
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Lossless conversion of images to PDF without unnecessarily re-encoding JPEG and
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JPEG2000 files. Thus, no loss of quality and no unnecessary large output file.
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background
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PDF is able to embed JPEG and JPEG2000 images as they are without re-encoding
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them (and hence loosing quality) but I was missing a tool to do this
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automatically, thus I wrote this piece of python code.
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If you know how to embed JPEG and JPEG2000 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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functionality
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-------------
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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 or JPEG2000
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file, it will be included as-is without any processing. If it is in any other
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format, the image will be included as zip-encoded RGB. As a result, this tool
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will be able to lossless wrap any image into a PDF container while performing
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better (in terms of quality/filesize ratio) than existing tools in case the
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input image is a JPEG or JPEG2000 file.
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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 or JPEG2000 file and can also not
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output a 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 JPEG and JPEG2000 files into a PDF container
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without adding more overhead than the PDF structure itself and will save all
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other graphics formats using lossless zip-compression.
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bugs
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----
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If you find a JPEG or JPEG2000 file that, when embedded can not be read by the
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Adobe Acrobat Reader, please contact me.
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For lossless conversion of other formats than JPEG or JPEG2000 files, zip/flate
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encoding is used. This choice is based on a number of tests I did on images.
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I converted them into PDF using imagemagick and all compressions it has to
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offer and then compared the output size of the lossless variants. In all my
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tests, zip/flate encoding performed best. You can verify my findings using the
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test_comp.sh script with any input image given as a commandline argument. If
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you find an input file that is outperformed by another lossless compression,
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contact me.
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