Method mask

src/image/p5.Image.js:1002–1052

(p5Image)

   */
  // TODO: - Accept an array of alpha values.
  mask(p5Image) {
    if (p5Image === undefined) {
      p5Image = this;
    }
    const currBlend = this.drawingContext.globalCompositeOperation;

    let imgScaleFactor = this._pixelDensity;
    let maskScaleFactor = 1;
    if (p5Image instanceof Renderer) {
      maskScaleFactor = p5Image._pInst._renderer._pixelDensity;
    }

    const copyArgs = [
      p5Image,
      0,
      0,
      maskScaleFactor * p5Image.width,
      maskScaleFactor * p5Image.height,
      0,
      0,
      imgScaleFactor * this.width,
      imgScaleFactor * this.height
    ];

    this.drawingContext.globalCompositeOperation = 'destination-in';
    if (this.gifProperties) {
      for (let i = 0; i < this.gifProperties.frames.length; i++) {
        this.drawingContext.putImageData(
          this.gifProperties.frames[i].image,
          0,
          0
        );
        this.copy(...copyArgs);
        this.gifProperties.frames[i].image = this.drawingContext.getImageData(
          0,
          0,
          imgScaleFactor * this.width,
          imgScaleFactor * this.height
        );
      }
      this.drawingContext.putImageData(
        this.gifProperties.frames[this.gifProperties.displayIndex].image,
        0,
        0
      );
    } else {
      this.copy(...copyArgs);
    }
    this.drawingContext.globalCompositeOperation = currBlend;
    this.setModified(true);
  }

  /**
   * Applies an image filter to the image.