Function blur

plugins/plugin-blur/src/index.ts:46–172

* A fast blur algorithm that produces similar effect to a Gaussian blur - but MUCH quicker * @param r the pixel radius of the blur * @example * ```ts * import { Jimp } from "jimp"; * * const image = await Jimp.read("test/image.png"); * * image.blur(5); * ```

(image: I, r: number)

   * ```
   */
  blur<I extends JimpClass>(image: I, r: number) {
    if (typeof r !== "number") {
      throw new Error("r must be a number");
    }

    if (r < 1) {
      throw new Error("r must be greater than 0");
    }

    let rsum: number;
    let gsum: number;
    let bsum: number;
    let asum: number;
    let x: number;
    let y: number;
    let i: number;
    let p: number;
    let p1: number;
    let p2: number;
    let yp: number;
    let yi: number;
    let yw: number;

    const wm = image.bitmap.width - 1;
    const hm = image.bitmap.height - 1;
    // const wh = image.bitmap.width * image.bitmap.height;
    const rad1 = r + 1;

    const mulSum = mulTable[r]!;
    const shgSum = shgTable[r]!;

    const red = [];
    const green = [];
    const blue = [];
    const alpha = [];

    const vmin = [];
    const vmax = [];

    let iterations = 2;

    while (iterations-- > 0) {
      yi = 0;
      yw = 0;

      for (y = 0; y < image.bitmap.height; y++) {
        rsum = image.bitmap.data[yw]! * rad1;
        gsum = image.bitmap.data[yw + 1]! * rad1;
        bsum = image.bitmap.data[yw + 2]! * rad1;
        asum = image.bitmap.data[yw + 3]! * rad1;

        for (i = 1; i <= r; i++) {
          p = yw + ((i > wm ? wm : i) << 2);
          rsum += image.bitmap.data[p++]!;
          gsum += image.bitmap.data[p++]!;
          bsum += image.bitmap.data[p++]!;
          asum += image.bitmap.data[p]!;
        }