Aseprite
Animated sprite editor & pixel art tool
... distortions when rotating tiny sprites. Create patterns repeating the image in a 3x3 grid. Create custom brushes for dithering. Composite layers to create color effects. Open or save a sequence of images. Create animations and save them as .gif files. Export your work to sprite sheets in .png and .json files. Recovery your sprites in case of crash. Integrate Aseprite in your assets pipeline with the command-line interface (CLI). Store several animations in one texture atlas.