Gretchen Leigh

Starting to dig into City Connection arcade's inner workings for... reasons, and the MAME driver has a hook into the init to convert text character graphics because the color for text characters isn't set per character but per scanline.

MAME citycon.cpp
void citycon_state::init_citycon()
{
	uint8_t *rom = memregion("gfx1")->base();

	/*
	  City Connection controls the text color code for each _scanline_, not
	  for each character as happens in most games. To handle that conveniently,
	  I convert the 2bpp char data into 5bpp, and create a virtual palette so
	  characters can still be drawn in one pass.
	  */
	for (int i = 0x0fff; i >= 0; i--)
	{
		rom[3 * i] = rom[i];
		rom[3 * i + 1] = 0;
		rom[3 * i + 2] = 0;
		int mask = rom[i] | (rom[i] << 4) | (rom[i] >> 4);
		if (i & 0x01) rom[3 * i + 1] |= mask & 0xf0;
		if (i & 0x02) rom[3 * i + 1] |= mask & 0x0f;
		if (i & 0x04) rom[3 * i + 2] |= mask & 0xf0;
	}
}

GitHub link