Datamax-O'Neil PrintPAD AN-05 (LP) User Manual
Page 2
We begin the compression with the first two bytes of ESC B (telling the printer we are using compressed graphics):
1B 42
The first three dotlines in our example are all white space. So this can be compressed into two bytes, ‘A’ or 0x41 for
Advance and 03 for 3 dotlines:
41 03
The next line contains graphics information, so we will need to use either compressed graphics or non-compressed
graphics. We will try compressed first:
Four 00’s will compress to the byte pair 00 04 (repeat 00 four times)
One 0F stands alone but still requires the byte pair 0F 01
Similarly, 80 requires 80 01, the four 00’s compress to 00 04, the two FF’s are represented by FF 02, the D2 requires D2
01, then we have 7 00’s which compress to 00 07, making the entire string 00 04 0F 01 80 01 00 04 FF 02 D2 01 00 07.
Note that if you add up all of the byte counts (4+1+1+4+2+1+7), it totals 20, the width of the printhead. We represent this
as compressed graphics by preceding it with a ‘G’ (0x47):
47 00 04 0F 01 80 01 00 04 FF 02 D2 01 00 07
Similarly, the next line could be represented as compressed:
47 00 03 0F 01 FF 02 C2 01 00 02 78 01 45 02 D2 03 F9 02 00 03
or non-compressed (preceded with a ‘U’ (0x55) using the same number of bytes.
55 00 00 00 0F FF FF C2 00 00 78 45 45 D2 D2 D2 F9 F9 00 00 00
Since the next line is “busier” than the preceding line, using RLE will probably make it longer (and we can see that it
does):
00 01 0F 01 F8 01 00 01 0E 01 E0 01 00 02 FF 02 01 01 E0 01 FF 01 D2 01… etc.,
so it is best represented as uncompressed:
55 00 0F F8 00 0E E0 00 00 FF FF 01 E0 FF D2 00 88 73 FC C7 00
The next two lines can each best be represented using a compressed line (note that 0x13 is 19 decimal):
47 00 01 FF 13
47 00 01 FF 13
And, the last two lines again can be compressed to only two bytes:
41 02
This is followed by the end code (printer returns to normal ASCII):
1B 45
And finally, we have the final compressed graphic ready to send to our mythical 20 byte wide printer (the example is
arranged to show each line on a separate line, but this is really one continuous string of 75 bytes):
1B 42
41 03
47 00 04 0F 01 80 01 00 04 FF 02 D2 01 00 07
47 00 03 0F 01 FF 02 C2 01 00 02 78 01 45 02 D2 03 F9 02 00 03
55 00 0F F8 00 0E E0 00 00 FF FF 01 E0 FF D2 00 88 73 FC C7 00
47 00 01 FF 13
47 00 01 FF 13
41 02
1B 45