Sega Digitizer System III "DIGITIZER 3 Ver2" format spec
Rich Whitehouse
2019-04-19

All atomic data is big-endian.

struct SDigHeader
{
	uint32_t mVer; //always 0x100 in known data
	uint16_t mImageCountHi; //always 0 in known data
	uint16_t mImageCount;
	uint32_t mDataSize;
	uint32_t mResv; //always 0 in known data
	char mId[16]; //"DIGITIZER 3 Ver2", not terminated
	uint8_t mPad[224];
};

//for each image:
	struct SDigImageHeader
	{
		uint16_t mDataOfsHi; //always 0 in known data
		uint16_t mDataOfs;
		uint16_t mOffsetX;
		uint16_t mOffsetY;
		uint16_t mWidth;
		uint16_t mHeight;
		uint16_t mColorIndex; //i think this is the palette entry to use for the index display, if applicable
		uint16_t mImageIndex;
		char mName[16]; //not terminated, trailed by spaces
	};

	struct SPaletteEntry
	{
		uint16_t mId; //each pixel entry will match one of these
		uint16_t mColor; //in Game Gear palette format, G4R4n4B4 
	};
	//there are at least 16 palette entries, but there may be more, which is why it's important to use mDataOfs to get to the start of pixel data.
	
	//pixel data is uint16_t * mWidth * mHeight, where each uint16_t matches one mId in the palette entries.

	//it's possible that the id bits have more significance than merely matching palette entries, perhaps with some special bit(s) to act as a mask.

	//the next SDigImageHeader will immediately follow the end of pixel data if more images are present.