1.高斯模糊(Gaussian blur)

原理：将图片插入到canvas中，将canvas中的图片，getImageData得到图片的像素值，用高斯模糊函数进像素值进行处理后，再把值putImageData放到canvas中，就实现了图片的高斯模糊处理。

高斯模糊函数中的逻辑：

注意：此处是window整个页面进行加载，不可以用img来调用onload方法，会报错：高斯函数未被定义的错误。

注意：getImageData、putImageData两个方法在服务器中使用有效。

HTML代码：

gauss

#data{

width: 400px;

height: 300px;

}

var oImg = document.getElementById('data');

var canvas = document.getElementById('canvas');

var ctx = canvas.getContext('2d');

var oData,newSrc;

window.onload = function () {

ctx.drawImage(oImg,0,0,400,300);

oData = ctx.getImageData(0,0,400,300);

newSrc = gaussBlur(oData);

ctx.putImageData(newSrc, 0, 0);

}

高斯模糊函数：

function gaussBlur(imgData) {

var pixes = imgData.data;

var width = imgData.width;

var height = imgData.height;

var gaussMatrix = [],

gaussSum = 0,

x, y,

r, g, b, a,

i, j, k, len;

var radius = 10;

var sigma = 5;

a = 1 / (Math.sqrt(2 * Math.PI) * sigma);

b = -1 / (2 * sigma * sigma);

//生成高斯矩阵

for (i = 0, x = -radius; x <= radius; x++, i++){

g = a * Math.exp(b * x * x);

gaussMatrix[i] = g;

gaussSum += g;

}

//归一化, 保证高斯矩阵的值在[0,1]之间

for (i = 0, len = gaussMatrix.length; i < len; i++) {

gaussMatrix[i] /= gaussSum;

}

//x 方向一维高斯运算

for (y = 0; y < height; y++) {

for (x = 0; x < width; x++) {

r = g = b = a = 0;

gaussSum = 0;

for(j = -radius; j <= radius; j++){

k = x + j;

if(k >= 0 && k < width){//确保 k 没超出 x 的范围

//r,g,b,a 四个一组

i = (y * width + k) * 4;

r += pixes[i] * gaussMatrix[j + radius];

g += pixes[i + 1] * gaussMatrix[j + radius];

b += pixes[i + 2] * gaussMatrix[j + radius];

// a += pixes[i + 3] * gaussMatrix[j];

gaussSum += gaussMatrix[j + radius];

}

}

i = (y * width + x) * 4;

// 除以 gaussSum 是为了消除处于边缘的像素, 高斯运算不足的问题

// console.log(gaussSum)

pixes[i] = r / gaussSum;

pixes[i + 1] = g / gaussSum;

pixes[i + 2] = b / gaussSum;

// pixes[i + 3] = a ;

}

}

//y 方向一维高斯运算

for (x = 0; x < width; x++) {

for (y = 0; y < height; y++) {

r = g = b = a = 0;

gaussSum = 0;

for(j = -radius; j <= radius; j++){

k = y + j;

if(k >= 0 && k < height){//确保 k 没超出 y 的范围

i = (k * width + x) * 4;

r += pixes[i] * gaussMatrix[j + radius];

g += pixes[i + 1] * gaussMatrix[j + radius];

b += pixes[i + 2] * gaussMatrix[j + radius];

// a += pixes[i + 3] * gaussMatrix[j];

gaussSum += gaussMatrix[j + radius];

}

}

i = (y * width + x) * 4;

pixes[i] = r / gaussSum;

pixes[i + 1] = g / gaussSum;

pixes[i + 2] = b / gaussSum;

}

}

//end

return imgData;

}

2. 刮刮乐

原理：将canvas背景用图片设置，canvas内容用刮刮乐灰色效果，然后鼠标按下、鼠标移动、鼠标抬起，完成清除canvas内容的操作

Document

var oCanvas = document.getElementById('canv'),

ctx = oCanvas.getContext('2d'),

w = oCanvas.width,

h = oCanvas.height,

lastPiont = {},

nowPoint = {};

function init(){

ctx.fillStyle = '#ccc';

ctx.fillRect(0, 0,w, h);

ctx.globalCompositeOperation = 'destination-out';

var img = new Image();

img.src = './1.jpeg';

img.onload = function(){

oCanvas.style.backgroundImage = 'url(' + img.src + ')';

oCanvas.addEventListener('mousedown', downFunc, false);

}

}

init();

function downFunc(e){

lastPiont.x = e.clientX - oCanvas.offsetLeft;

lastPiont.y = e.clientY - oCanvas.offsetTop;

oCanvas.addEventListener('mousemove', moveFunc, false);

document.addEventListener('mouseup', upFunc, false);

}

function moveFunc(e){

nowPoint.x = e.clientX - oCanvas.offsetLeft;

nowPoint.y = e.clientY - oCanvas.offsetTop;

ctx.beginPath();

ctx.fillStyle = 'red';

ctx.lineWidth = 40;

ctx.lineCap = 'round';

ctx.moveTo(lastPiont.x, lastPiont.y);

ctx.lineTo(nowPoint.x, nowPoint.y);

ctx.stroke();

ctx.arc(nowPoint.x, nowPoint.y, 20, 0, Math.PI *2);

ctx.closePath();

ctx.fill();

lastPiont.x = nowPoint.x;

lastPiont.y = nowPoint.y;

}

function upFunc(){

oCanvas.removeEventListener('mousemove', moveFunc, false);

document.removeEventListener('mouseup', upFunc, false);

clearCanvas();

}

function clearCanvas(){

var d = ctx.getImageData(0, 0, w, h),

c = 0,

len = d.data.length;

for(var i = 0; i < len; i += 4){

if(d.data[i] === 0){

c++;

}

}

if(c > len/4 *0.7){

ctx.clearRect(0, 0, w, h);

}

}