Basic usage: Press the "Load PNG" button and enter the text of a base64-encoded PNG file. (Ideally a fairly small one! Think like, small-scale pixel art, or like, icons or something.) You can also change some parameters for how to display the image; hopefully those are mostly self-explanatory, except maybe image scale being set to "0", which actually means that the scale will be chosen automatically. Once the image is loaded, you can move your mouse to the top-left corner to find a button that lets you export the image in the format used by projects such as my image editor: https://scratch.mit.edu/projects/163440219/
TurboWarp can be used to avoid size/speed limitations: https://turbowarp.org/418046248 (images bigger than the stage still aren't accounted for when rendering though) If you want to use this in your own project, look in the "png reader" sprite and read the comment in there for instructions. One thing to note though is that because of the list length limit, an RGBA image that's bigger than about 200x200 won't work and you'll get an "Unexpected end of image data" error. That's probably something that I *could* fix, but this project is kind of purposeless anyway. :-P (Not to mention impractical for big images since it's so slow.....)