Function getIndexedFrame

src/image/loading_displaying.js:431–449

    // key collisions.
    const paletteCache = {};
    const getIndexedFrame = frame => {
      const length = frame.length / 4;
      const index = new Uint8Array(length);
      for (let i = 0; i < length; i++) {
        const key =
          (frame[i * 4] << 24) |
          (frame[i * 4 + 1] << 16) |
          (frame[i * 4 + 2] << 8) |
          frame[i * 4 + 3];
        if (paletteCache[key] === undefined) {
          paletteCache[key] = nearestColorIndex(
            globalPalette,
            frame.slice(i * 4, (i + 1) * 4)
          );
        }
        index[i] = paletteCache[key];
      }
      return index;
    };

    // the way we designed the palette means we always take the last index for transparency
    const transparentIndex = globalPalette.length - 1;