Function autocrop

plugins/plugin-crop/src/index.ts:99–279

* Autocrop same color borders from this image. * This function will attempt to crop out transparent pixels from the image. * * @example * ```ts * import { Jimp } from "jimp"; * * const image = await Jimp.read("test/image.png"); * const cropped = image.autocrop(); * ```

(image: I, options: AutocropOptions = {})

   * ```
   */
  autocrop<I extends JimpClass>(image: I, options: AutocropOptions = {}) {
    const {
      tolerance = 0.0002,
      cropOnlyFrames = true,
      cropSymmetric = false,
      leaveBorder = 0,
      ignoreSides: ignoreSidesArg,
    } = typeof options === "number"
      ? ({ tolerance: options } as AutocropComplexOptions)
      : AutocropComplexOptionsSchema.parse(options);
    const w = image.bitmap.width;
    const h = image.bitmap.height;
    const minPixelsPerSide = 1; // to avoid cropping completely the image, resulting in an invalid 0 sized image

    // i.e. north and south / east and west are cropped by the same value
    const ignoreSides = {
      north: false,
      south: false,
      east: false,
      west: false,
      ...ignoreSidesArg,
    };

    /**
     * All borders must be of the same color as the top left pixel, to be cropped.
     * It should be possible to crop borders each with a different color,
     * but since there are many ways for corners to intersect, it would
     * introduce unnecessary complexity to the algorithm.
     */

    // scan each side for same color borders
    let colorTarget = image.getPixelColor(0, 0); // top left pixel color is the target color
    const rgba1 = intToRGBA(colorTarget);

    // for north and east sides
    let northPixelsToCrop = 0;
    let eastPixelsToCrop = 0;
    let southPixelsToCrop = 0;
    let westPixelsToCrop = 0;

    // north side (scan rows from north to south)
    colorTarget = image.getPixelColor(0, 0);
    if (!ignoreSides.north) {
      north: for (let y = 0; y < h - minPixelsPerSide; y++) {
        for (let x = 0; x < w; x++) {
          const colorXY = image.getPixelColor(x, y);
          const rgba2 = intToRGBA(colorXY);

          if (colorDiff(rgba1, rgba2) > tolerance) {
            // this pixel is too distant from the first one: abort this side scan
            break north;
          }
        }

        // this row contains all pixels with the same color: increment this side pixels to crop
        northPixelsToCrop++;
      }
    }