balloc, bfree, rdbitmap, wrbitmap, rdbitmapfile, wrbitmapfile - allocating, freeing, read-
ing, writing bitmaps
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)
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.
graphics(2), bitblt(2), bit(3), bitmap(6)
These functions return 0 on failure, usually due to insufficient memory.
May set errstr.
Ldepth must be 0, 1, 2, or 3.