Sega Game Gear

Color palette

The Game Gear uses 12-bit RGB color (4 bits per channel), quadrupling the Master System’s 6-bit palette from 64 to 4,096 possible colors. Internally the VDP stores colors in BGR444 format across two CRAM (Color RAM) palettes of 16 entries each: one for background tiles and one for sprites, giving 32 simultaneous on-screen colors.

Since the Game Gear’s palette is defined by RGB bit-depth rather than a fixed lookup table, bitmapped generates the full 4,096-color gamut at runtime using enumerateColorSpace():

import { enumerateColorSpace } from 'bitmapped/presets';
 
const ggColorSpace = {
  type: 'programmable',
  bitsPerChannel: 4,
  totalBits: 12,
  format: 'BGR444',
  maxSimultaneous: 32,
};
 
// All 4,096 possible Game Gear colors
const fullPalette = enumerateColorSpace(ggColorSpace);

Each 4-bit channel maps to 16 intensity levels (0-15), expanded to 8-bit values via bit replication (e.g., 0x7 becomes 0x77). This gives a smooth, evenly spaced gamut across all three channels.

The key constraint: per-tile palette

The Game Gear inherits the Master System’s tile-based VDP (Video Display Processor). The background layer is composed of 8x8 pixel tiles, and each tile references one of the two 16-color palettes stored in CRAM. Sprites similarly draw from the second 16-color palette.

This means each 8x8 tile on screen is limited to 16 colors from its assigned palette. While the 12-bit gamut allows far more vibrant and varied color choices than the SMS, the fundamental constraint remains: only 32 colors can appear simultaneously, and each tile must commit to one palette.

bitmapped’s per-tile-palette constraint solver handles this by analyzing each 8x8 tile region and selecting the optimal subpalette assignment to minimize color error across the image:

Interactive demo

Code example

import { process } from 'bitmapped';
import { getPreset, enumerateColorSpace } from 'bitmapped/presets';
 
const gg = getPreset('game-gear')!;
 
// Enumerate the full 4,096-color gamut from the color space definition
const fullPalette = enumerateColorSpace(gg.colorSpace!).map(
  (color) => ({ color })
);
 
const result = process(imageData, {
  blockSize: 4,
  palette: fullPalette,
  dithering: 'bayer',
  distanceAlgorithm: 'redmean',
  constraintType: 'per-tile-palette',
  tilePaletteConfig: {
    tileWidth: 8,
    tileHeight: 8,
    subpaletteCount: 2,
    colorsPerSubpalette: 16,
  },
});

Presets

bitmapped includes one Game Gear preset:

• game-gear — 160x144, 12-bit BGR444 color space, backlit LCD display emulation