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WalterPlinge
33 lines
1.7 KiB
Odin
33 lines
1.7 KiB
Odin
/*
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Formats:
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PBM (P1, P4): Portable Bit Map, stores black and white images (1 channel)
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PGM (P2, P5): Portable Gray Map, stores greyscale images (1 channel, 1 or 2 bytes per value)
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PPM (P3, P6): Portable Pixel Map, stores colour images (3 channel, 1 or 2 bytes per value)
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PAM (P7 ): Portable Arbitrary Map, stores arbitrary channel images (1 or 2 bytes per value)
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PFM (Pf, PF): Portable Float Map, stores floating-point images (Pf: 1 channel, PF: 3 channel)
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Reading
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All formats fill out header fields `format`, `width`, `height`, `channels`, `depth`
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Specific formats use more fields
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PGM, PPM, and PAM set `maxval`
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PAM also sets `tupltype`, and is able to set `channels` to an arbitrary value
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PFM sets `scale` and `little_endian`
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Currently doesn't support reading multiple images from one binary-format file
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Writing
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All formats require the header field `format` to be specified
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Additional header fields are required for specific formats
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PGM, PPM, and PAM require `maxval`
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PAM also uses `tupltype`, though it may be left as default (empty or nil string)
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PFM requires `scale` and `little_endian`, though the latter may be left untouched (default is false)
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Some syntax differences from the specifications:
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`channels` stores what the PAM specification calls `depth`
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`depth` instead stores how many bytes will fit `maxval` (should only be 1, 2, or 4)
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`scale` and `little_endian` are separated, so the `header` will always store a positive `scale`
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`little_endian` will only be true for a negative `scale` PFM, every other format will be false
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`little_endian` only describes the netpbm data being read/written, the image buffer will be native
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*/
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package netpbm
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