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import { isNodePattern, throwError } from "@jimp/utils";
/**
* Masks a source image on to this image using average pixel colour. A completely black pixel on the mask will turn a pixel in the image completely transparent.
* @param {Jimp} src the source Jimp instance
* @param {number} x the horizontal position to blit the image
* @param {number} y the vertical position to blit the image
* @param {function(Error, Jimp)} cb (optional) a callback for when complete
* @returns {Jimp} this for chaining of methods
*/
export default () => ({
mask(src, x = 0, y = 0, cb) {
if (!(src instanceof this.constructor)) {
return throwError.call(this, "The source must be a Jimp image", cb);
}
if (typeof x !== "number" || typeof y !== "number") {
return throwError.call(this, "x and y must be numbers", cb);
}
// round input
x = Math.round(x);
y = Math.round(y);
const w = this.bitmap.width;
const h = this.bitmap.height;
const baseImage = this;
src.scanQuiet(
0,
0,
src.bitmap.width,
src.bitmap.height,
function (sx, sy, idx) {
const destX = x + sx;
const destY = y + sy;
if (destX >= 0 && destY >= 0 && destX < w && destY < h) {
const dstIdx = baseImage.getPixelIndex(destX, destY);
const { data } = this.bitmap;
const avg = (data[idx + 0] + data[idx + 1] + data[idx + 2]) / 3;
baseImage.bitmap.data[dstIdx + 3] *= avg / 255;
}
}
);
if (isNodePattern(cb)) {
cb.call(this, null, this);
}
return this;
},
});
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