package core:image/netpbm

Source

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

Index