Graphic filters

I begin to fall in love with JavaScript and HTML5. You can access your Webcam with JS! As an example, I've implemented some graphic filters.

Basics

HTML5

You need:

This is the bare minimum HTML code you need for valid HTML:

<!DOCTYPE html>
<html>
    <head>
        <title>Some title</title>
    </head>
    <body>
        <video autoplay id="vid" style="display:none;"></video>
        <canvas id="canvas" width="640" height="480"></canvas>
        <script type="text/javascript" src="graphic-filter.js">
        </script>
    </body>
</html>

JavaScript

Important functions / datastructures are:

getUserMedia: see support by browsers
ImageData: WTF? The image is a ONE dimensional array of integers in 0, ..., 255. So the first 4 array elements describe the pixel (0|0) with its RGBA value

A starting point for your code might be:

'use strict';

var video = document.querySelector("#vid");
var canvas = document.querySelector('#canvas');
var context = canvas.getContext('2d');
var localMediaStream = null;

var onCameraFail = function (e) {
    console.log('Camera did not work.', e);
};

setInterval(function snapshot() {
    if (localMediaStream) {
        context.drawImage(video, 0, 0);
        var width = 640;
        var height = 480;
        var imgDataNormal = context.getImageData(0, 0, width, height);
        var imgData = context.createImageData(width, height);

        // convert image to grayscale
        for (var i = 0; i < imgData.width*imgData.height*4; i += 4) {
            var r = imgDataNormal.data[i + 0];
            var g = imgDataNormal.data[i + 1];
            var b = imgDataNormal.data[i + 2];
            var brightness = (3*r+4*g+b)>>>3;
            imgData.data[i] = brightness;
            imgData.data[i+1] = brightness;
            imgData.data[i+2] = brightness;
        }

        context.putImageData(imgData, 0, 0);
    }
}, 500);

navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia;
window.URL = window.URL || window.webkitURL;
navigator.getUserMedia({video:true}, function (stream) {
    video.src = window.URL.createObjectURL(stream);
    localMediaStream = stream;
}, onCameraFail);
console.log(localMediaStream);