Dithertron

Try it online!

This interactive web-based tool converts full-color images to full-screen 8-bit retro formats, performing cropping, resizing, palette selection, and dithering.

Some formats (e.g. C64 multicolor, TMS9918A, ZX Spectrum, NES 5-color) split the screen into smaller sub-blocks that each can only display 2 to 4 colors of a larger palette. Neighboring sub-blocks may affect each other when dithering is enabled, so Dithertron chooses good colors for each sub-block and iterates until they stabilize.

For modes with constrained palette choices (e.g. C64 Hires, ZX Spectrum, MSX/Coleco) it might help to reduce the Dither parameter, otherwise the dither errors will accumulate and create blocky splotches.

How To Use

Upload an image, or select an example image from the pulldown.
Choose a target format.
Play with the sliders until you're happy with the result.
Download the final image (PNG), download a binary file, or open an image viewer code sample in 8bitworkshop.

Graphics Formats

These formats will export a sample 8bitworkshop project that displays the image:

C-64 Multi - 160 x 200, 16 colors, 4 colors per 4x8 block
C-64 Hires - 320 x 200, 16 colors, 2 colors per 8x8 block
NES (4 color, 240 tiles) - 160 x 96, 4 out of 64 colors
TMS9918A (Mode 2) - 256 x 192, 16 colors, 2 colors per 8x1 block
Apple ][ Hires - 140 x 192, 6 colors, 4 colors per 7x1 block
Atari ANTIC D - 160 x 96, 4 out of 256 colors
Atari VCS - 40 x 192, 2 out of 256 colors
Bally Astrocade - 160 x 98, 4 out of 256 colors
ZX Spectrum - 256 x 192, 8 colors, 2 colors per 8x8 block
Amstrad CPC (mode 0) - 160 x 200, 16 out of 27 colors
Amstrad CPC (mode 1) - 320 x 200, 4 out of 27 colors

Other formats:

NES (4 color, full screen) - 256 x 240, 4 out of 64 colors
NES (5 color, full screen) - 256 x 240, 5 out of 64 colors
Atari 7800 (160A) - 160 x 240, 4 out of 256 colors
Atari 7800 (160B) - 160 x 240, 12 out of 256 colors
Sega Master System - 176 x 144, 16 out of 64 colors
BBC Micro (mode 2) - 160 x 256, 8 colors
Apple ][ Double-Hires - 140 x 192, 16 colors
Apple ][ Lores - 40 x 48, 16 colors
Fairchild Channel F - 102 x 58, 4 out of 4 colors
Mac 128K - 512 x 342, monochrome
PC CGA Modes - 320 x 200, 4 colors
PC EGA Mode 0Dh - 320 x 200, 16 out of 16 colors
PC EGA Mode 10h - 640 x 350, 16 out of 16 colors
Williams Arcade - 304 x 256, 16 out of 256 colors
PICO-8 - 128 x 128, 16 colors
TIC-80 - 240 x 136, 16 colors
Game Boy Classic - 160 x 144, 4 colors
Commander X16 - 320 x 240, 256 colors out of 4096
Commander X16 - 640 x 400 (cropped to fit in VRAM), 16 colors out of 4096
Amiga Lores - 320 x 256, 32 colors out of 4096
Amiga Lores HAM6 - 320 x 256, 4096 colors via HAM

Development

Install modules:

npm i

Build:

./node_modules/.bin/tsc

Then open index.html in browser.

TODO

Palette editing
Search for optimal crop window
Check pixel-exact source images
Interlaced modes (VCS color)
Refresh retains mode settings
Custom width and height (crop rect for non-full-screen)
Faster closest color lookup

SAMPLE IMAGES

https://www.pexels.com/photo/dreamy-black-woman-in-bright-headscarf-near-rough-wall-4615699/ https://www.pexels.com/photo/creative-graffiti-wall-with-portrait-of-frida-kahlo-6424244/

miniupnp / dithertron