grafX2/misc/c64viewer/README.md

picview.asm (c) 2019 Thomas Bernard

This is a C64 image depacker and viewer designed to build self-displaying .prg pictures files. One has to concatenate the data to the viewer machine code to build a .prg file.

Data format

• 1 byte for mode
• then one or several blocks, composed of :
  1. 1 byte TP header :
     • upper nibble T is type
     • lower nibble P is packing
  2. n bytes data load, depending of type and packing

Mode byte

0EBM0000 E=Extended Background mode. B=Bitmap Mode. M=Multicolor.

TP byte

• T = type
  • 0 - end of file
  • 1 - bitmap 8000 bytes
  • 2 - screen ram 1000 bytes
  • 3 - color ram 1000 bytes at $D800
  • 4 - border/background etc. 15 bytes at $D020
• P = packing
  • 0 - no packing
  • 1 - RLE packing
  • 2 - color ram RLE packing

All other values are reserved.

border/backgrounds at $D020, 15 bytes

• BO BORDER
• BA BACKGROUND
• E1 Extra background color #1
• E2 Extra background color #2
• E3 Extra background color #3
• SE1 sprite extra color #1
• SE2 sprite extra color #2
• S0 sprite #0
• S1 sprite #1
• S2 sprite #2
• S3 sprite #3
• S4 sprite #4
• S5 sprite #5
• S6 sprite #6
• S7 sprite #7