RLE_GETROW(3) 3 (2/2/87) RLE_GETROW(3)
NAME
rle_getrow - Read a scanline of pixels from an RLE file.
SYNOPSIS
#include <rle.h>
rle_getrow( the_hdr, rows );
rle_hdr * the_hdr;
rle_pixel ** rows;
DESCRIPTION
Rle_getrow reads information for a single scanline from the
input file each time it is called. The_hdr should point to
the structure initialized by rle_get_setup(3). The array
rows should contain pointers to arrays of characters, into
which the scanline data will be written. There should be as
many elements in rows as there are primary colors in the
input file (typically 1 or 3), and the scanline arrays must
be indexable up to the maximum X coordinate, as specified by
the_hdr->xmax. rle_getrow returns the y value of the
scanline just read. This will always be 1 greater than the
y value from the scanline previously read, and starts at
the_hdr->ymin. Only those channels enabled by the_hdr->bits
will be returned.
NOTES
If an alpha channel is present in the input and enabled (by
RLE_SET_BIT, see rle_hdr(3)), then rows should include a -1
entry. (I.e., rows[-1] should point to a valid scanline
array.) The easiest way to ensure this is to use
rle_row_alloc(3) to allocate rows.
Rle_getrow will continue to return scanlines even after the
end of the input file has been reached, incrementing the
return scanline number each time it is called. The calling
program should use some other termination criterion (such as
the scanline number reaching the_hdr->ymax, or explicitly
testing testing for end of file on the input with
feof(infile). The second test may fail if rle_getrow has
encountered a logical EOF in the file. The first will
always work eventually.)
EXAMPLE
The code below reads the first two 3 color scanlines of 512
pixels from an RLE file on the standard input.
char scanline[2][3][512], *rows[3];
int row, i;
rle_dflt_hdr.rle_file = stdin;
rle_get_setup( &rle_dflt_hdr );
for ( row = 0; row < 2; row++ )
{
Page 1 (printed 12/1/98)
RLE_GETROW(3) 3 (2/2/87) RLE_GETROW(3)
for ( i = 0; i < 3; i++ )
rows[i] = scanline[row][i];
rle_getrow( &rle_dflt_hdr, rows );
}
SEE ALSO
rle_hdr(3), rle_row_alloc(3), rle_row_free(3),
rle_get_setup(3), rle_getraw(3), rle_getskip(3),
rle_putrow(3), librle(3), RLE(5).
AUTHOR
Spencer W. Thomas, Todd Fuqua
University of Utah
Page 2 (printed 12/1/98)
