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34 lines
1.9 KiB
Odin
34 lines
1.9 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` (maximum of 65535)
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PAM sets `tupltype` if there is one, and can set `channels` to any value (not just 1 or 3)
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PFM sets `scale` (float equivalent of `maxval`) and `little_endian` (endianness of stored floats)
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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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You can use your own `Netpbm_Info` struct to control how images are written
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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` (maximum of 65535)
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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 optionally `little_endian`
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Some syntax differences from the specifications:
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`channels` stores the number of values per pixel, what the PAM specification calls `depth`
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`depth` instead is the number of bits for a single value (32 for PFM, 16 or 8 otherwise)
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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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