Paxar 9474 manual E a r I m a g e B u f f e r, M p r e s s i n g t h e D a t a S t r e a m

C l e a r I m a g e B u f f e r

This command clears all or selective graphics from the image buffer. Once graphic data is sent to the printer, that graphic stays in memory until a clear image buffer command is sent.

Syntax	{ C## }
F i e l d	Contents
C	Must be the letter ‘C’ to identify the clear image buffer
	command.
##	This optional parameter specifies a particular graphic to be
	cleared from memory. It must match the number assigned in
	the graphic data stream. If omitted, ALL graphics in memory
	will be deleted.
Example	{C} Clears all graphics from the printer.
	{C4} Clears only graphic number 4.

C o m p r e s s i n g t h e D a t a S t r e a m

Image data usually consists of a large amount of repetitive data. Therefore, the printer uses a data compression algorithm for the graphic message structure. Here’s how it works.

1.Any image is defined as a matrix of cells.

2.Each row of the matrix consists of a series of consecutive ON (black) or OFF (white) cells. The range is 1-26, represented by adding either a hex 40 (black) or hex 60 (white). Cells that print black are represented by the upper case letters ‘A’ through ‘Z’ in the file sent to the printer. Cells that print white are represented by the lowercase letters ‘a’ through ‘z’ in the file. Consecutive cells greater than 26 require multiple letters.

Example: 39 consecutive white cells are represented by the letters ‘zm’ (i.e. ‘z’ produces 26 white cells followed by ‘m’ or 13 more white cells).

4-8 Using Graphics