https://padayani.com/assets/front_area/infinityslider/js/canvasgrayscale.js

1/*
2
3CanvasGrayscale - InfinitySlider Extension
4Version: 1.0
5Author: Epeo
6Website: demo.epeo.it/infinityslider
7
8*/
9function canvasGrayscale (valuecanvas, valuewidth, valueheight) {
10	var canvas  = valuecanvas;
11	var width = valuewidth;
12	var height = valueheight;
13
14	var context = canvas.getContext("2d");
15	imageData = context.getImageData(0, 0, width, height);
16	px = imageData.data;
17	length = px.length;
18
19	for (var i = 0; i < length; i += 4) {
20	gray = px[i] * .3 + px[i + 1] * .59 + px[i + 2] * .11;
21	px[i] = px[i + 1] = px[i + 2] = gray;
22	}
23
24	context.putImageData(imageData, 0, 0);
25}