showimage(7) [plan9 man page]

SHOWIMAGE(7)						 Miscellaneous Information Manual					      SHOWIMAGE(7)

NAME

       showimage - bitmap displayer, colormap changer

SYNOPSIS

       showimage [ option ] [ file ...	]

DESCRIPTION

       Showimage  displays the bitmap contained in file in the top left corner of the current window.  It goes to the next file when any character
       is typed, exiting when there are no more files.	The options, all of which require no file, are:

       -c     Load the standard Plan 9 colormap, if this is an 8-bit display.  The standard colormap takes the value of a pixel byte and uses  the
	      top 3 bits for red darkness, the next 3 bits for green darkness, and the final 2 for blue darkness.  So 0 is white and 255 is black.
	      Exceptions: pixels 85 and 170 are intermediate grey values, so that 2-bit-per-pixel grey scale images look right.

       -g     Load the colormap with a linear grey scale, from 0 (white) to max (black).

       -r     Load the colormap with a reverse linear grey scale, from 0 (black) to max (white).

       -mmapfile
	      Load the colormap from the file mapfile.	See rgbpix(2) for the format.

       -d     Dump the current colormap to standard output in the format of rgbpix(2).

FILES

       /lib/image
	      Some sample pictures.

SOURCE

       /sys/src/cmd/showimage.c

SEE ALSO

       graphics(2), rgbpix(2), intro(9), getmap(9.1)

																      SHOWIMAGE(7)

RGBPIX(2)							System Calls Manual							 RGBPIX(2)

NAME

       RGB, rgbpix, rdcolmap, wrcolmap - handle color screens

SYNOPSIS

       #include <u.h>
       #include <libc.h>
       #include <libg.h>

       ulong rgbpix(Bitmap *b, RGB rgb)

       void  rdcolmap(Bitmap *b, RGB *map)

       void  wrcolmap(Bitmap *b, RGB *map)

DESCRIPTION

       Colors are described by the red, green, and blue light intensities, in an RGB datum:

	      typedef
	      struct RGB {
		    ulong red;
		    ulong green;
		    ulong blue;
	      } RGB;

       Black is represented by zero in all three positions and white has the maximum unsigned long value in all three positions.

       Some  of  the graphics functions, such as point (see bitblt(2)), take a pixel value argument, which is a single unsigned long.  For a given
       bitmap, rgbpix returns the pixel value with a color closest to the color represented by the rgb argument.

       There is a colormap associated with each Bitmap.  A colormap is an array of RGBs, of length 2^(2^ldepth), giving the colors for	pixels	0,
       1, 2, etc.

       Rdcolmap  reads	the colormap for the given bitmap into the provided map, which must have enough space to hold it.  Wrcolmap associates the
       given colormap with the given bitmap, if possible.  (The hardware might not allow this.)

SOURCE

       /sys/src/libg

SEE ALSO

       graphics(2)

BUGS

       These functions work only for the screen bitmap.  This interface will have to be refined for screens with more than 8 bits per pixel.

																	 RGBPIX(2)