index.js
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import { isNodePattern, throwError } from '@jimp/utils';
/**
* Applies a minimum color threshold to a greyscale image. Converts image to greyscale by default
* @param {number} options object
* max: A number auto limited between 0 - 255
* replace: (optional) A number auto limited between 0 - 255 (default 255)
* autoGreyscale: (optional) A boolean whether to apply greyscale beforehand (default true)
* @param {number} cb (optional) a callback for when complete
* @return {this} this for chaining of methods
*/
export default () => ({
threshold({ max, replace = 255, autoGreyscale = true }, cb) {
if (typeof max !== 'number') {
return throwError.call(this, 'max must be a number', cb);
}
if (typeof replace !== 'number') {
return throwError.call(this, 'replace must be a number', cb);
}
if (typeof autoGreyscale !== 'boolean') {
return throwError.call(this, 'autoGreyscale must be a boolean', cb);
}
max = this.constructor.limit255(max);
replace = this.constructor.limit255(replace);
if (autoGreyscale) {
this.greyscale();
}
this.scanQuiet(0, 0, this.bitmap.width, this.bitmap.height, (x, y, idx) => {
const grey =
this.bitmap.data[idx] < max ? this.bitmap.data[idx] : replace;
this.bitmap.data[idx] = grey;
this.bitmap.data[idx + 1] = grey;
this.bitmap.data[idx + 2] = grey;
});
if (isNodePattern(cb)) {
cb.call(this, null, this);
}
return this;
}
});