6.3.13. Horizontal 1200-dpi image format mode (Raster Graphic Mode 1027)- Page 119

CHAPTER 2 PCL - 99 

<Compressed Image Data> 

Data compression compresses the original image data word by word (16 bits). 

The compressed data consists of both horizontal compression which uses 16 bit, 8 bit and 4 bit repeating 
patterns within 1 word or 2 words of data and vertical compression which indicates how many times to repeat 
the same data as in the previous line within 1 word of data. 



 Non-compressed data 

When the most significant bit in the first 2 bytes is 0, the printer goes into non-compression mode. The 
following 11 bits then indicate the number of words of data, the least significant 4 bits are not used. After that, 
the image data follows word by word. 

   15    14 

   4   3   

   0 

0 

data word count (11 bits) 

not used 

data 1 (16 bits) 

: 

data n (16 bits) 



 16 bit repeating compressed data 

When the most significant 3 bits in the first 2 bytes are in the order 1, 0, 0, the remaining 13 bits indicate the 
number of times to repeat 16 bit data. The following 2 bytes should be the 16 bit data to repeat. 

   15     14    13    12 

  0 

1 

0 

0 

number of repeats(13 bits) 

data to repeat(16 bits) 



 8 bit repeating compressed data 

When the most significant 3 bits in the first 2 bytes are in the order 1, 1, 0, the following 5 bits indicate the 
number of times to repeat 16 bit (two by 8 bits) data. The remaining 8 bits should be the 8 bit data to repeat. 

   15    14    13    12 

           8    7 

0 

1 

1 

0 

number of repeats 

data to repeat(8 bits) 

   (5 

bits) 



 4 bit repeating compression data 

When the most significant 3 bits in the first 2 bytes are in the order 1, 0, 1, the following 4 bits are the 4 bit data 
to repeat. The remaining 9 bits indicate the number of times to repeat the 16 bit (4 by 4 bits) data. 

   15    14    13    12 

           9    8 

0 

1 

0 

1 

data to repeat 

number or repeats(9 bits) 

   (4 

bits) 



 Vertical repeating compressed data 

When the most significant 3 bits in the first 2 bytes are in the order 1, 1, 1, the remaining 13 bits indicate the 
same data words as in the previous line. 

   15    14    13    12 

0 

1 

1 

1 

the same data words as in the previous line (13 bits) 

The printer cannot support the APT and HRC function in the 1200 dpi printing mode.