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)

voidbfree(Bitmap ∗b)

voidrdbitmap(Bitmap ∗b, int ymin, int ymax, uchar ∗data)

voidwrbitmap(Bitmap ∗b, int ymin, int ymax, uchar ∗data)

Bitmap∗rdbitmapfile(int fd)

voidwrbitmapfile(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 arguments, 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. 

Plan 9  —  April 04, 1995