NES / Famicom

Color palette

The NES PPU generates color via NTSC composite video — there is no single “correct” RGB palette. bitmapped uses a 2C02 PPU reference palette. The 64-entry lookup table is organized as 4 rows of 16, encoding brightness × hue:

The key constraint: 16×16 attribute blocks

The NES nametable uses attribute bytes that assign one of four background palettes to each 16×16 pixel region (a 2×2 group of 8×8 tiles). Every pixel within that block must use colors from the same 4-color palette.

This forces color boundaries to align to a coarse grid — it’s why NES games have that distinctive blocky color look, where you can often see rectangular regions of different color sets.

bitmapped’s attribute-block constraint solver divides the image into 16×16 blocks and selects the optimal 4-color subpalette for each block, minimizing color error.

Interactive demo

Code example

import { process } from 'bitmapped';
import { getPreset } from 'bitmapped/presets';
 
const nes = getPreset('nes-ntsc')!;
 
const result = process(imageData, {
  blockSize: 4,
  palette: nes.palette!,
  dithering: 'floyd-steinberg',
  distanceAlgorithm: 'redmean',
  constraintType: 'attribute-block',
  attributeBlockConfig: {
    width: 16,
    height: 16,
    maxColors: 4,
  },
});

Presets

bitmapped includes two NES presets:

• nes-ntsc — NTSC timing (256×240), 2C02 PPU palette
• nes-pal — PAL timing (256×239), same palette