Datamax-O'Neil PrintPAD AN-05 (LP) - Manual (Page 3)

Using RLE we have compressed a 200 byte file into only 75 bytes making it only 37.5% of its original size!
THE ALGORITHM:
The input to this algorithm must be a bit mapped graphic of the same width (N BYTES) as the printhead used for
printing.
1. Start the RLE compressed graphic with ESC B (0x1B, 0x42)
2. Scan the next dotline of N bytes, replacing each byte by a byte pair where the 1
st byte is the byte in the
original graphic and the second byte is the number of times that is repeated. Call the length of this sequence
of bytes M
3. IF the line was all 00’s [result of (2) is 00 N] and the previous line was not all zeros, then add ‘A’ (0x41)
followed by a count C of 01
ELSE IF the line was all 00’s [result of 2 is 00 N] and the previous line was all zeros, then increment the count
C by 1
ELSE IF M <= (N) then add ‘G’ (0x47) followed by the NEW sequence of pairs of bytes to the compressed
graphic string (M bytes)
ELSE add ‘U’ (0x55) followed by the ORIGINAL bytes (N bytes)
4. Repeat 2 and 3 until all dotlines have been processed
5. End the RLE compressed graphic with ESC E (0x1B, 0x45)