75 lines
5.0 KiB
Plaintext
75 lines
5.0 KiB
Plaintext
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(U<>]<5D>0 <00> J @ sz d Z ddddddddd dd
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d d d d
dd dd dd d
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dd d d dd d
dd d d d dd
dd d d d d ddd d d d d d d d d d d d d d g@dddd dd d d dddd dd d d dddddd d d d d dd
d d d d dddd d d d d d d d d d d d d d d d d d d d d d d d d d d d d g@gd<17>dddddd ddddddd dd d dddd dd d d d dd dd d d!d d"d dd d dd#d"d"dd d d!d#d"d"d"dd d d d"d"d"d"ddd d"d"d"d"d"g@d$d d$ddd d d%d d&d
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d$dd d dd$d
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dd'd ddd
dd$d'dddd
d"ddd ddd%d"d"d d ddd%d(d"d"d d dd
d"d"d"d"d%dd
d"d"d"d"d"g@gd<17>d)d*d+d+d*d,dddd+d-d-d*d.d/ddd+d-d-d*d/dd0d&d*d*d*ddd d&dd,d.d/ddddddd/dd ddddddd0d&ddddddd&dddddg@d1d1d dd dddd1dddddddd dd$dddddddddddddd dddddddddddddddddddddddddddddddg@gd<17>d)ddddd2d+d-d*ddddd2d+d-d*ddddd+d-d1d,dddd+d-d1d,dd2d2d+d-d.d/ddd+d+d-d1d/dddd-d-d1d,ddddd*d*d,dddddg@d2d2d-d,d d d d d2d+d*dd0dddd-d*d,d0ddddd,dd0dddddd d0ddddddd dddddddd dddddddd dddddddg@gd<17>d)d3d3d3d3d3d3d3d3d3d3d3d3d3d3d3d3d3d3d3d3d3d3d3dd3d3d3d3d3d3ddd3d3d3d3d3ddd2d3d3d3d3ddd2d2d3d3d3ddd2d2d2d3d3ddd2d2d2d2g@d3d3d3ddd2d2d2d3d3d3dd2d2d2d2d3d3d3d2d2d2d2d2ddd2d2d2d2d2d2dd2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2d2g@gd<17>dd
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d0d0ddd d4d$d0ddd&d d ddd0dd$dd ddddd&dd dddddd d dddddd d ddddddd4dddddddd$dddddddg@dd&d'dddd$d$d&dd d0d0dddd'd d0d0dddddd0d0ddddddd0ddddddddddddddd$dddddddd$dddddddg@gd<17>ddd.d.dd$ddd$d.d,d,dd d&ddd.d,d/dd&dddddddddddd$d d&ddddddd&ddddddddddddddd$dddddddg@d dd dddd$d$dd0d0d0d0dddd d0d0d0dddddd0d0ddddddd0ddddddddddddddd$dddddddd$dddddddg@gd<17>d)d*d+d+d*d,dddd+d-d-d*d.d/ddd+d-d-d*d/dddd*d*d*dddddd,d.d/ddddddd/ddddddddddddddddddddddg@d1d1d dddd$d$d1ddd0d0dddd dd0d0dddddd0d0ddddddd0ddddddddddddddd$dddddddd$dddddddg@gd<17>d)ddddd2d+d-d*ddddd2d+d-d*ddddd+d-d1d,dddd+d-d1d,dd2d2d+d-d.d/ddd+d+d-d1d/dddd-d-d1d,ddddd*d*d,dddddg@d2d2d-d,d d d d d2d+d*d/d0dddd-d*d,d0ddddd,d/d0dddddd d0ddddddd dddddddd dddddddd dddddddg@gd<17>d5<64> Zd6S )7ai
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JPEG quality settings equivalent to the Photoshop settings.
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More presets can be added to the presets dict if needed.
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Can be use when saving JPEG file.
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To apply the preset, specify::
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quality="preset_name"
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To apply only the quantization table::
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qtables="preset_name"
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To apply only the subsampling setting::
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subsampling="preset_name"
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Example::
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im.save("image_name.jpg", quality="web_high")
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Subsampling
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-----------
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Subsampling is the practice of encoding images by implementing less resolution
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for chroma information than for luma information.
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(ref.: https://en.wikipedia.org/wiki/Chroma_subsampling)
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Possible subsampling values are 0, 1 and 2 that correspond to 4:4:4, 4:2:2 and
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4:2:0.
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You can get the subsampling of a JPEG with the
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`JpegImagePlugin.get_subsampling(im)` function.
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Quantization tables
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-------------------
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They are values use by the DCT (Discrete cosine transform) to remove
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*unnecessary* information from the image (the lossy part of the compression).
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(ref.: https://en.wikipedia.org/wiki/Quantization_matrix#Quantization_matrices,
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https://en.wikipedia.org/wiki/JPEG#Quantization)
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You can get the quantization tables of a JPEG with::
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im.quantization
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This will return a dict with a number of arrays. You can pass this dict
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directly as the qtables argument when saving a JPEG.
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The tables format between im.quantization and quantization in presets differ in
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3 ways:
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1. The base container of the preset is a list with sublists instead of dict.
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dict[0] -> list[0], dict[1] -> list[1], ...
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2. Each table in a preset is a list instead of an array.
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3. The zigzag order is remove in the preset (needed by libjpeg >= 6a).
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You can convert the dict format to the preset format with the
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`JpegImagePlugin.convert_dict_qtables(dict_qtables)` function.
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Libjpeg ref.:
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https://web.archive.org/web/20120328125543/http://www.jpegcameras.com/libjpeg/libjpeg-3.html
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<EFBFBD> <00> <00> <00> <00>' <00>2 <00>. <00>> <00>D <00> <00> <00>& <00>5 <00>A <00> <00> <00> <00>6 <00> <00> <00>+ <00>B )Z subsamplingZ quantization<6F> <00> <00> <00> <00> <00>
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