CPC Guide - Graphics formatGraphics
Defining graphics
This shows how the pixels are formed. 
  Mode 0 
  Mode 1 
  Mode 2 



Mode 0
In mode 0, there are 2 pixels per byte. Each pixel can be one of 16 colours. 
(The pixel is 4 times the size of a mode 2 pixel). 

The pixels are numbered p1 and p2. p1 is the left pixel, p2 is the right pixel. 
p1 and p2 contain a number in the range 0..15. 
        Screen Byte
                +--+--+--+--+--+--+--+--+
                |7.|6 |5.|4 |3.|2 |1.|0 |
                |..|  |..|  |..|  |..|  |
                +--+--+--+--+--+--+--+--+
                 ^     ^     ^     ^
                 |     |     |     |
                 |  ___|     |     |
                 |  |  ______|     |
                 |__|__|___        |
                    |  |  |        |
                  __|__|__|________|
                 |  |  |  |
                 |  |  |  |
                +--+--+--+--+
                |3 |2 |1 |0 |
                |  |  |  |  |
                +--+--+--+--+
                     p1


                        Byte
                +--+--+--+--+--+--+--+--+
                |7 |6,|5 |4,|3 |2,|1 |0,|
                |  |,,|  |,,|  |,,|  |,,|
                +--+--+--+--+--+--+--+--+
                    ^     ^     ^     ^
                    |     |     |     |
                    |  ___|     |     |
                    |  |  ______|     |
                    |__|__|___        |
                       |  |  |        |
                     __|__|__|________|
                    |  |  |  |
                    |  |  |  |
                   +--+--+--+--+
                   |3 |2 |1 |0 |
                   |  |  |  |  |
                   +--+--+--+--+
                        p2

Mode 1
In mode 1, there are 4 pixels per byte. Each pixel can be one of 4 colours. (The 
pixel is 2 times the size of a mode 2 pixel). 

The pixels are numbered p1, p2, p3 and p4. p1 is the leftmost pixel, and p4 is 
the rightmost pixel. p1,p2,p3,p4 contain a number in the range 0..3. 

Note: In this mode the pixels are square. 
        Screen Byte
                +--+--+--+--+--+--+--+--+
                |7.|6 |5 |4 |3.|2 |1 |0 |
                |..|  |  |  |..|  |  |  |
                +--+--+--+--+--+--+--+--+
                 ^           ^
                 |           |
                 |           |
                 |__         |
                    |        |
                  __|________|
                 |  |
                +--+--+ p1
                |1 |0 |
                |  |  |
                +--+--+

        Screen Byte
                +--+--+--+--+--+--+--+--+
                |7 |6,|5 |4 |3 |2,|1 |0 |
                |  |,,|  |  |  |,,|  |  |
                +--+--+--+--+--+--+--+--+
                    ^           ^
                    |           |
                    |           |
                    |__         |
                       |        |
                     __|________|
                    |  |
                   +--+--+ p2
                   |1 |0 |
                   |  |  |
                   +--+--+

        Screen Byte
                +--+--+--+--+--+--+--+--+
                |7 |6 |5-|4 |3 |2 |1-|0 |
                |  |  |--|  |  |  |--|  |
                +--+--+--+--+--+--+--+--+
                       ^           ^
                       |           |
                       |           |
                       |__         |
                          |        |
                        __|________|
                       |  |
                      +--+--+ p3
                      |1 |0 |
                      |  |  |
                      +--+--+

        Screen Byte
                +--+--+--+--+--+--+--+--+
                |7 |6 |5 |4*|3 |2 |1 |0*|
                |  |  |  |**|  |  |  |**|
                +--+--+--+--+--+--+--+--+
                          ^           ^
                          |           |
                          |           |
                          |__         |
                             |        |
                           __|________|
                          |  |
                         +--+--+ p4
                         |1 |0 |
                         |  |  |
                         +--+--+

Mode 2
In mode 2, there are 8 pixels per byte. Each pixel can be one of 2 colours. Each 
bit of the byte is a pixel. If the bit value is 0, then pen 0 is used, if the 
bit value is 1, then pen 1 is used. 

The pixels are numbered p1, p2, p3, p4, p5, p6, p7 and p8. p1 is the leftmost 
pixel and p8 is the rightmost pixel. p1,p2,p3,p4,p5,p6,p7,p8 contain 0 or 1. 

The bits for each pixel are shown below: 
                        Byte
                +--+--+--+--+--+--+--+--+
                |7 |6 |5 |4 |3 |2 |1 |0 |
                |  |  |  |  |  |  |  |  |
                +--+--+--+--+--+--+--+--+
                 ^  ^  ^  ^  ^  ^  ^  ^        +--+
                 |  |  |  |  |  |  |  |______  |0 | p8
                 |  |  |  |  |  |  |           |  |
                 |  |  |  |  |  |  |           +--+
                 |  |  |  |  |  |  |
                 |  |  |  |  |  |  |__________ +--+
                 |  |  |  |  |  |              |0 | p7
                 |  |  |  |  |  |              |  |
                 |  |  |  |  |  |              +--+
                 |  |  |  |  |  |
                 |  |  |  |  |  |_____________ +--+
                 |  |  |  |  |                 |0 | p6
                 |  |  |  |  |                 |  |
                 |  |  |  |  |                 +--+
                 |  |  |  |  |
                 |  |  |  |  |________________ +--+
                 |  |  |  |                    |0 | p5
                 |  |  |  |                    |  |
                 |  |  |  |                    +--+
                 |  |  |  |
                 |  |  |  |___________________ +--+
                 |  |  |                       |0 | p4
                 |  |  |                       |  |
                 |  |  |                       +--+
                 |  |  |
                 |  |  |______________________ +--+
                 |  |                          |0 | p3
                 |  |                          |  |
                 |  |                          +--+
                 |  |
                 |  |_________________________ +--+
                 |                             |0 | p2
                 |                             |  |
                 |                             +--+
                +--+
                |0 | p1
                |  |
                +--+