Export to a binary file

[sdsnatcher]

To make it easier to implement support in PC viewers like the RECOIL library, it would be ideal to have a standardised binary format for the SMS images and export images on this format.

It can be very a simple VRAM dump, so support can be easily implemented on emulators too. And the format allows easy binary inclusion for game development. The INCBIN would only have to skip the header and the VDP registers tail.

Here goes a humble proposal:

1. Header (6 bytes signature):
   1.1) Signature

• "MSBMP" string for the SMS
• "GGBMP" string for the GG
• "TMBMP" string for the TMS9918 (SG-1000, ColecoVision, MSX1, TI-99A, etc)
  1.2) Version (1 byte): 0 = v1.0
  1.3) File offset to the metatada area (1 byte): 9
  1.4) File offset to the data area (16bit, little endian)

2. Metadata area (if no metadata is present, must contain only the end marker)
   2.1) Author name: ASCII text, ends with 0Dh,0Ah
   2.2) Title: ASCII text, ends with 0Dh,0Ah
   2.3) Notes: ASCII text (might be empty)
   2.4) End of the metadata marker: 1Ah (mandatory)
3. Data area
   3.1) VDP registers dump: 10h bytes (SG-1000 uses only the first 7. Fill the unused bytes with zeroes)
   3.2) CRAM dump: 64 bytes (SMS uses only the first 32, SG-1000 uses none. Fill the unused bytes with zeroes)
   3.3) VRAM dump: 16384 bytes with a raw VRAM dump

The file extension could be .SBM, meaning "Sega Bitmap".

[maxim-zhao]

Interesting, a long time ago I wrote a program to support Windows thumbnails (in Windows XP, the interface has since changed) from Meka savestates using the same principle (render from VRAM contents) but it fell down because it could not restore any raster effects.

[sdsnatcher]

Indeed, raster effects won't be supported. But at least title screens and other static bitmaps could be easily dumped this way.