BALLOC(2) 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 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 bit-
map 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 exter-
nal 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
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BALLOC(2) BALLOC(2)
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 insuffi-
cient memory.
May set errstr.
BUGS
Ldepth must be 0, 1, 2, or 3.
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