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/*
Readers and writers for `PBM`, `PGM`, `PPM`, `PAM` and `PFM` images.
Formats:
PBM (P1, P4): Portable Bit Map, stores black and white images (1 channel)
PGM (P2, P5): Portable Gray Map, stores greyscale images (1 channel, 1 or 2 bytes per value)
PPM (P3, P6): Portable Pixel Map, stores colour images (3 channel, 1 or 2 bytes per value)
PAM (P7 ): Portable Arbitrary Map, stores arbitrary channel images (1 or 2 bytes per value)
PFM (Pf, PF): Portable Float Map, stores floating-point images (Pf: 1 channel, PF: 3 channel)
Reading:
- All formats fill out header fields `format`, `width`, `height`, `channels`, `depth`.
- Specific formats use more fields:
PGM, PPM, and PAM set `maxval` (maximum of 65535)
PAM sets `tupltype` if there is one, and can set `channels` to any value (not just 1 or 3)
PFM sets `scale` (float equivalent of `maxval`) and `little_endian` (endianness of stored floats)
- Currently doesn't support reading multiple images from one binary-format file.
Writing:
- You can use your own `Netpbm_Info` struct to control how images are written.
- All formats require the header field `format` to be specified.
- Additional header fields are required for specific formats:
PGM, PPM, and PAM require `maxval` (maximum of 65535)
PAM also uses `tupltype`, though it may be left as default (empty or nil string)
PFM requires `scale`, and optionally `little_endian`
Some syntax differences from the specifications:
- `channels` stores the number of values per pixel, what the PAM specification calls `depth`
- `depth` instead is the number of bits for a single value (32 for PFM, 16 or 8 otherwise)
- `scale` and `little_endian` are separated, so the `header` will always store a positive `scale`
- `little_endian` will only be true for a negative `scale` PFM, every other format will be false
- `little_endian` only describes the netpbm data being read/written, the image buffer will be native
*/
package netpbm
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