getting around to prototyping a thing. baby steps
ouuhhh yeahhh UI design is my passion
putting that number input inline with the checkbox that it's tied to felt pretty good
it's starting to look like a Gizmo. like a Doohickey
The functionality you are looking has been kicked around in various ECMAScript proposals, however it does not appear to be coming anytime soon.
aaururrghghahauagurgh 
O.K. here's a very early release. only Atkinson is implemented right now and only uploading a file to serve as palette. have fun
fixed some bugs (namely the one where a palette wouldn't load half the time) and detached the control feedback from the image processing to make moving sliders on long operations less painful at the tradeoff of not having immediate output preview
yesterday i don't think this dithering was taking a whole 3 seconds, so now i need to chase down optimizations
if for every pixel in an image i do a comprehensive color distance check for every color in a palette, a 320x240 picture takes ~3000ms
if i cache the results of the closest palette color to each color and fetch those when available instead of calculating, it takes... ~3800ms
YESSS yes yes LUTs to the rescue
i've made sliders automatically update the preview again
this version is now live at the previous link
i'm cheating a little bit truncating 8 bits of color into 6 bits to make the LUT manageable, but since the point of the tool is to reduce colorspace anyway it shouldn't be much of a problem
ohhh yeahhhh
let's see if i implement the other dithering modes tonight or if i just keep playing with this and doing no work
well floyd-steinberg was easy to implement
here's a cool little picture in 640x480 with only the 16 EGA colors. you could set this as your windows 95 wallpaper
OK OK i finally implemented bayer
if i can get some work done on palettes (add built-ins, sampling from image) i'm properly releasing an initial version
OK here is a first release!!!
https://maple.pet/ditherinator #ditherinator
i gave up for now on quantizing colors from the source image bc it's harder than i thought, but you can still upload your own palette PNGs and use the built-in ones
HAVE FUN AND SHOW ME COOL PICTURES
@mavica_again This feels like it was shared on CompuServe in the early '90s. I love it.
i need to build a palette LUT on load.