PCL
2-65
Group 3 and Group 4 Raster Compression
Since Group 4 images do not use line endings, the width of the image must be
specified using the Raster Width command (
ESC
*r#S).
The compressed image data is sent to the printer using the Transfer Raster Data
command (
ESC
*b#W). The maximum number of bytes that can be sent using the
Transfer Raster Data command is 32K bytes. Images larger than 32K bytes must be
broken up and sent using multiple commands. It does not matter where the image is
broken, or how many Transfer Raster Data commands are used. Once the image is
started (with a Transfer Raster Data command), no other commands are allowed until
the entire image has been sent.
The following example prints a Group 4 image file that is 256 bits wide and 9,645 bytes
long:
ESC
*b1002M |Set Raster Compression to Group 4
ESC
*r256S |Define width of image in input bits
ESC
*r1A |Start Raster Graphics at current position
ESC
*b9645W |9,645 bytes of a Group 4 image
...[Group 4 image data]...
ESC
*rB |End Raster Graphics
All lines of data must be the same length. If they are not, zeroes (0) must be added to
attain the same length.
Note: If the uncompressed image extends beyond the logical page dimensions or
beyond the raster width specified in the Raster Width command (
ESC
*r#S), the
image is clipped at print time.
Additional Compression Modes
When the compression mode is 1008 (Lexmark Adaptive), TIFF word and double-
word can be printed using compression scan modes 254 and 255 respectively. This
compression method sends a raster image as a block of raster data.
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