plan9 man page for picfile

PICFILE(9.6)															      PICFILE(9.6)

NAME
       picfile - raster graphic image format

DESCRIPTION
       Files  in  this	format	store  images  represented as two-dimensional arrays of multiple-channel pixels.  A picfile consists of an textual
       header followed by binary data encoding the pixels in row-major order.  The header is a list of attribute/value	pairs  separated  by  new-
       lines,  terminated  by  an  empty  line.  Each header line has the form name=value.  The name may not contain an ASCII NUL, newline, or the
       value may not contain NUL or newline.  The last line of a header is empty.

       The standard attributes are described below; all but TYPE and WINDOW are optional.  TYPE must come first; otherwise  order  is  irrelevant.
       As  any unrecognized attribute is passed over uninterpreted by all standard software, applications are welcome to include arbitrary annota-
       tions, such as SHOESIZE=101/2, if they wish.

       TYPE=type
	      How the pixels are encoded.  Standard types are
	      runcode
		     A run-length encoding.  The data are a sequence of (nchan+1)-byte records each containing a count k and nchan bytes giving  a
		     pixel value to be repeated k+1 times.  A run may not span scanlines.
	      dump   A two-dimensional array of nchan-byte records in row major order.
	      bitmap One-bit pixels, packed into bytes high bit leftmost.  Zero bits are white, one bits are black.  Rows are padded with zeros to
		     a multiple of 16 bits.
	      ccitt-g4
		     A black-and-white image under CCITT FAX Group 4 compression.  This format is highly compressive on images of  text  and  line
		     art.  Similarly, and for Group 3, 1-D and 2-D.
	      pico   A sequence of nchan two-dimensional arrays of single bytes.
	      ccir601
		     Pixels are in dump order, 2 bytes per pixel encoded according to the IEEE digital component video standard.
       WINDOW=x0 y0 x1 y1
	      The  x,y	coordinates  of  the  upper  left corner and the point just diagonally outside the lower right corner, x increasing to the
	      right, y down.
       NCHAN=nchan
	      The number of channels, default 1.
       CHAN=channels
	      The names of the channels.  Channels should be nchan characters long.  Certain substrings of channels are conventionally	understood
	      by  most programs that read and write picture files: m is a monochrome image channel, rgb is a full-color image, a is an alpha chan-
	      nel, and z...  is a floating point (four-byte, single precision) z value.  Some very old	monochrome  pictures  have  CHAN=r.   This
	      usage is deprecated but still recognized by some programs.
       RES=x y
	      The digitizing resolution horizontally and vertically, in pixels/inch.

       CMAP=  (The  value  is empty.)  A color map, a 256x3-byte translation table for color values, follows the header.  In a full-color picture,
	      each color-map row maps pixel values of the corresponding channel.  In a monochrome picture, pixel values index  the  color  map	to
	      yield red, green and blue, like this:

	      uchar cmap[256][3];
	      red = cmap[pixel][0];
	      green = cmap[pixel][1];
	      blue = cmap[pixel][2];

EXAMPLES
       sed '/^$/q' image
	      Print a header.  A sample header follows.

       TYPE=dump
       WINDOW=0 0 512 512
       NCHAN=1
       CHAN=m
       RES=300 300
       CMAP=
       COMMAND= antiquantize 'halftone CLASSIC' 512.halftone LIBERTY.anticlassic
       COMMAND=  halftone CLASSIC 512.liberty 512.halftone 1.75 512.halftone
       COMMAND=   transpose IN OUT
       COMMAND=    resample 512 IN OUT
       COMMAND=     transpose IN OUT
       COMMAND=      resample 512 IN OUT
       COMMAND=       clip 400 400 LIBERTY OUT

SEE ALSO
       bitmap(6)
       Tom Duff, ``Raster Graphics in Plan 9''

																      PICFILE(9.6)