Spectrum 512 Painter
A GEM-style paint program for Atari ST/STE workflows, running entirely in the browser using HTML5 Canvas and WebGL.
Supports Spectrum 512 color conversion with multiple dither presets and targets for ST (512 colors), STE (4096), and STE Enhanced (32768).
Source code and documentation:
github.com/AnimaInCorpore/Spectrum512Painter