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

1. Upload an image, or select an example image from the pulldown.

2. Choose a target format.

3. Play with the sliders until you're happy with the result.

4. 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

To clone just the main branch:

git clone -b master --single-branch git@github.com:sehugg/8bitworkshop.git

Install modules:

npm i

Build:

make setup      (or "make setupwin" on Windows)
npm run build

Watch:

make watch

Then open http://localhost:8189 in browser.

Dev version: https://sehugg.github.io/dithertron

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

License

Copyright © 2016-2023 Steven Hugg.

This project is GPL-3.0 licensed.

Dependencies retain their original licenses.

All exported code is licensed under CC0.

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/