rgbpix(2) [plan9 man page]

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)

BALLOC(2)							System Calls Manual							 BALLOC(2)

NAME

       balloc, bfree, rdbitmap, wrbitmap, rdbitmapfile, wrbitmapfile - allocating, freeing, reading, writing bitmaps

SYNOPSIS

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

       Bitmap *balloc(Rectangle r, int ldepth)

       void   bfree(Bitmap *b)

       void   rdbitmap(Bitmap *b, int ymin, int ymax, uchar *data)

       void   wrbitmap(Bitmap *b, int ymin, int ymax, uchar *data)

       Bitmap *rdbitmapfile(int fd)

       void   wrbitmapfile(int fd, Bitmap *b)

DESCRIPTION

       A  new  bitmap is allocated with balloc; it will have the extent and ldepth (log base 2 of the number of bits per pixel) given by its argu-
       ments, and will be filled with zeros. The id field will have been set to the identifying number used by /dev/bitblt (see bit(3)),  and  the
       cache  field will be zero.  Balloc returns 0 if the server has run out of bitmap resources.  Bfree frees the resources used by its argument
       bitmap.

       The remaining functions deal with moving groups of pixel values between bitmaps and user space or external files.  There is a fixed  format
       for the exchange and storage of bitmap data (see bitmap(6)).

       Rdbitmap reads rows of pixels from bitmap b into data.  The rows read have y=ymin,ymin+1, ...  ymax-1.  Those rows must be within the range
       allowed by b.r.

       Wrbitmap replaces the specified rows of pixels in bitmap b with data.

       Rdbitmapfile creates a bitmap from data contained an external file (see bitmap(6) for the file format); fd is a file descriptor obtained by
       opening such a file for reading.  The returned bitmap is allocated using balloc.

       Wrbitmapfile writes bitmap b onto file descriptor fd, which should be open for writing.	The format is as described for rdbitmapfile.

       Rdbitmapfile and wrbitmapfile do not close fd.

SOURCE

       /sys/src/libg

SEE ALSO

       graphics(2), bitblt(2), bit(3), bitmap(6)

DIAGNOSTICS

       These functions return 0 on failure, usually due to insufficient memory.

       May set errstr.

BUGS

       Ldepth must be 0, 1, 2, or 3.

																	 BALLOC(2)