==  GRAPHICS INTERCHANGE FORMAT

GrafX2 format of predilection is GIF.

GrafX2 uses the GIF89a spec for saving :
https://www.w3.org/Graphics/GIF/spec-gif89a.txt

it supports a few extensions :
* NETSCAPE animation extension
* GFX2PATH original path saving extension
* GFX2MODE Special Drawing mode saving extension
* CRNG     Color cycling extension


== NETSCAPE animation extension
see http://www.vurdalakov.net/misc/gif/netscape-looping-application-extension

== GFX2PATH
Stores the original file path.
This is used by the backup system.

The format is :

{{{
0x21       Extension Label
0xFF       Application Extension Label
0x0B       Block Size
"GFX2PATH" Application Identifier (8 bytes)
"\0\0\0"   Application Authentication Code (3 bytes)
0xll       Sub-block Data Size : path size (including null)
"..path.." path (null-terminated)
0xll       Sub-block Data Size : filename size (including null)
"..file.." file name (null-terminated)
0x00       Block terminator
}}}

== GFX2MODE
extension to store ::IMAGE_MODES :

{{{

0x21       Extension Label
0xFF       Application Extension Label
0x0B       Block Size
"GFX2MODE" Application Identifier (8 bytes)
"2.6"      Application Authentication Code (3 bytes)
0xll       Sub-block Data Size
string     label
...        More sub blocks can be added in the future
0x00 Block terminator
}}}

Supported values (as of GrafX2 2.6) :
* "LAYERED" (not written)
* "ANIMATION" (not written)
* "ZX_SPECTRUM"
* "GAMEBOYCOLOR"
* "THOMSON40COL"
* "CPC_EGX"
* "CPC_EGX2"
* "CPC_MODE5"
* "CPC_RASTER"
* "C64_HIRES"
* "C64_MULTICOLOR"
* "C64_FLI"
* "APPLE2_HGR"
* "APPLE2_DHGR"

== CRNG color cycling extension
Same content as a CRNG [wiki:Develop/FileFormats/IFF IFF] chunk


{{{
0x21       Extension Label
0xFF       Application Extension Label
0x0B       Block Size
"CRNG\0\0\0\0" "CRNG" Application Identifier (8 bytes)
"1.0"      Application Authentication Code (3 bytes)
0xll       Sub-block Data Size (6 bytes per color cycle)
For each color cycle :
  0xRRRR   (big endian) Rate
  0xFFFF   (big endian) Flags
  0xSS     start (lower color index)
  0xEE     end (higher color index)
0x00       Block terminator

}}}