⎕PNG

[Dr . Jürgen Sauermann]

    Hi,
      
      I would like to announce a new GNU APL feature: ⎕PNG
      
      PNG stands for "Portable Network Graphics" and is a file format,
      standardized
      in RFC 2083, for (still) images that is, among several other use
      cases, also
      directly understood by web browsers.
      
      Unlike some of the other image file formats around, the PNG file
      format
      has no strings attached, such as patents or copyrights. This was
      one of the
      reasons for choosing it in GNU APL.
      
      While APL appears to be the perfect choice for manipulating the
      large pixel
      arrays of images, this is not the case for the files on disc from
      which the pixel
      arrays are read or eventually stored. ⎕PNG tries to close this
      gap.
      
      ⎕PNG is comprised of three simple sub-function for:
      
      1. reading a .png file into an APL array of pixels,
      2. displaying such an array in a GTK window on the screen, and
      3. writing a (supposedly somehow manipulated) pixel array into a .png
      file.
      
      The main work in the conversions above is actually provided by libpng
      (see
      www.libpng.org)
      therefore ⎕PNG is merely a lightweight wrapper around
      libpng. ⎕PNG is supposed to support all file variants
      (colour and grayscale,
      different pixel resolutions from 1 to 16 bits, with or without
      alpha channel),
      on input and most (= all but pixel arrays using colour palettes)
      on output.
      
      SVN 1589, see also info apl section 2.32 for
      details.
      
      Enjoy,
      Jürgen