package core:image/netpbm

Source

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

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