Netpbm (PBM, PGM, PPM, PAM, PFM)

Egami reads and writes the Netpbm formats: P1 to P6, plain and binary, at maxval 1 to 65,535, P7 PAM with alpha, and the PF and Pf float maps.

A file loads as Gray8, Gray16, GrayAlpha8, Rgb8, Rgba8 or Rgba16, and a float map as RgbF32 or GrayF32.

// Auto: P5 (PGM) for gray, P6 (PPM) for color, P7 (PAM) when the pixel type has alpha.
image.Save("duck.ppm");

// The plain-text forms, for tools that read them; lines are at most 70 characters.
image.Save("duck-plain.ppm", new PnmWriterOptions { PlainText = true });

// A 1-bit bitmap, thresholded at 50% gray.
image.Save("duck.pbm", new PnmWriterOptions { Kind = PnmKind.Bitmap });

Maxvals other than 255 and 65,535 are scaled exactly, as round(v × 255 / maxval). A PAM with an unknown tuple type is read by its depth, with a warning. A stream with several images reads the first and warns. # comments become Comment text entries and are written back. Saving to a .pbm, .pgm, .ppm, .pam or .pfm path writes that variant unless PnmWriterOptions.Kind names one; .pnm chooses from the pixel type.

PFM float maps load as RgbF32 (PF) or GrayF32 (Pf), marked as linear light, with their scale and byte order in PnmDetails; values outside 0..1 are kept. Writing uses PFM for float types without alpha, or when PnmKind.FloatMap is asked for: little-endian, scale −1, as Netpbm and ImageMagick write it.