PlayStation 1

Color palette

The PS1 GPU uses a 15-bit framebuffer in BGR555 format — 5 bits per channel, yielding 32,768 possible colors. Unlike older consoles with fixed color lookup tables, the PS1 has no palette indirection for 3D rendering. The GPU rasterizes polygons directly into the framebuffer at full 15-bit color depth.

Textures, however, support three storage formats:

• 4-bit CLUT — 16-color palette per texture, used heavily to conserve VRAM
• 8-bit CLUT — 256-color palette per texture
• 15-bit direct — full color, no palette lookup

Most PS1 games use 4-bit and 8-bit CLUT textures to fit more data into the limited 1 MB of VRAM, with the CLUT palettes themselves stored in VRAM as well.

The key constraint: PS1 ordered dither

The PS1 GPU applies a characteristic ordered dither pattern when rendering Gouraud-shaded polygons. Internal color interpolation runs at higher precision than the 15-bit framebuffer output, so the GPU uses a fixed asymmetric 4×4 dither matrix to reduce color banding. This produces the distinctive cross-hatch noise visible in virtually every PS1 game with smooth shading.

The hardware dither matrix, applied per-channel before truncating 8-bit values to 5-bit:

PS1_DITHER_MATRIX = [
  [-4,  0, -3,  1],
  [ 2, -2,  3, -1],
  [-3,  1, -4,  0],
  [ 3, -1,  2, -2],
]

Note the asymmetry — this is not a standard Bayer matrix. The values range from -4 to +3, and the pattern repeats every 4 pixels in both dimensions. Each value is added to the 8-bit channel value (then clamped to 0-255) before the 8-to-5-bit truncation. This is what gives PS1 rendering its unmistakable grainy texture, especially visible in dark gradients and Gouraud-shaded surfaces.

bitmapped reproduces this with the 'ps1-ordered' dithering algorithm, applying the same matrix used by the original hardware.

Interactive demo

Code example

import { process } from 'bitmapped';
import { getPreset } from 'bitmapped/presets';
 
const ps1 = getPreset('ps1')!;
 
const result = process(imageData, {
  blockSize: 1,
  palette: ps1.palette!,
  dithering: 'ps1-ordered',
  distanceAlgorithm: 'euclidean',
});

Presets

bitmapped includes one PS1 preset:

• ps1 — 320×240 mode, 15-bit BGR555 color space, PS1 ordered dither