小试牛刀，实现了六款简单常见HTML5 Canvas特效滤镜，并且封装成一个纯JavaScript可调用的API文件gloomyfishfilter.js。支持的特效滤镜分别为：
1.反色
2.灰色调
3.模糊
4.浮雕
5.雕刻
6.镜像
滤镜原理解释：
1.反色：获取一个像素点RGB值r, g, b则新的RGB值为(255-r, 255-g, 255-b)
2.灰色调：获取一个像素点RGB值r, g, b则新的RGB值为
newr = (r * 0.272) + (g * 0.534) + (b * 0.131);
newg = (r * 0.349) + (g * 0.686) + (b * 0.168);
newb = (r * 0.393) + (g * 0.769) + (b * 0.189);
3.模糊：基于一个5*5的卷积核
4.浮雕与雕刻：
基于当前像素的前一个像素RGB值与它的后一个像素的RGB值之差再加上128
5.镜像：模拟了物体在镜子中与之对应的效果。
杂项准备
1.如何获取Canvas 2d context对象
var canvas = document.getElementById("target");
canvas.width = source.clientWidth;
canvas.height = source.clientHeight;
if(!canvas.getContext) {
console.log("Canvas not supported. Please install a HTML5compatible browser.");
return;
}
// get 2D context of canvas and draw image
tempContext = canvas.getContext("2d");
2.如何绘制一个DOM img对象到Canvas对象中
var source = document.getElementById("source");
tempContext.drawImage(source, 0, 0, canvas.width,canvas.height);
3.如何从Canvas对象中获取像素数据
var canvas = document.getElementById("target");
varlen = canvas.width * canvas.height * 4;
var canvasData = tempContext.getImageData(0, 0, canvas.width, canvas.height);
var binaryData = canvasData.data;
4.如何对DOM对象实现鼠标Click事件绑定
function bindButtonEvent(element, type, handler)
{
if(element.addEventListener){
element.addEventListener(type, handler,false);
}else {
element.attachEvent('on'+type, handler);// for IE6,7,8
}
}
5.如何调用实现的gfilter API完成滤镜功能
<scriptsrc="gloomyfishfilter.js"></script> //导入API文件
gfilter.colorInvertProcess(binaryData, len); //调用 API
6.浏览器支持：IE, FF, Chrome上测试通过，其中IE上支持通过以下标签实现：
<meta http-equiv="X-UA-Compatible"content="chrome=IE8">
效果演示：
应用程序源代码：
CSS部分：
#svgContainer {
width:800px;
height:600px;
background-color:#EEEEEE;
}
#sourceDiv { float: left; border: 2px solid blue}
#targetDiv { float: right;border: 2px solid red}
filter1.html中HTML源代码：
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="X-UA-Compatible" content="chrome=IE8">
<meta http-equiv="Content-type" content="text/html;charset=UTF-8">
<title>Canvas Filter Demo</title>
<link href="default.css" rel="stylesheet" />
<script src="gloomyfishfilter.js"></scrip>
</head>
<body>
<h1>HTML Canvas Image Process - By Gloomy Fish</h1>
<div id="svgContainer">
<div id="sourceDiv">
<img id="source" src="../test.png" />
</div>
<div id="targetDiv">
<canvas id="target"></canvas>
</div>
</div>
<div id="btn-group">
<button type="button" id="invert-button">反色</button>
<button type="button" id="adjust-button">灰色调</button>
<button type="button" id="blur-button">模糊</button>
<button type="button" id="relief-button">浮雕</button>
<button type="button" id="diaoke-button">雕刻</button>
<button type="button" id="mirror-button">镜像</button>
</div>
</body>
</html>
filter1.html中JavaScript源代码：
var tempContext = null; // global variable 2d context
window.onload = function() {
var source = document.getElementById("source");
var canvas = document.getElementById("target");
canvas.width = source.clientWidth;
canvas.height = source.clientHeight;
if (!canvas.getContext) {
console.log("Canvas not supported. Please install a HTML5 compatible browser.");
return;
}
// get 2D context of canvas and draw image
tempContext = canvas.getContext("2d");
tempContext.drawImage(source, 0, 0, canvas.width, canvas.height);
// initialization actions
var inButton = document.getElementById("invert-button");
var adButton = document.getElementById("adjust-button");
var blurButton = document.getElementById("blur-button");
var reButton = document.getElementById("relief-button");
var dkButton = document.getElementById("diaoke-button");
var mirrorButton = document.getElementById("mirror-button");
// bind mouse click event
bindButtonEvent(inButton, "click", invertColor);
bindButtonEvent(adButton, "click", adjustColor);
bindButtonEvent(blurButton, "click", blurImage);
bindButtonEvent(reButton, "click", fudiaoImage);
bindButtonEvent(dkButton, "click", kediaoImage);
bindButtonEvent(mirrorButton, "click", mirrorImage);
}
function bindButtonEvent(element, type, handler)
{
if(element.addEventListener) {
element.addEventListener(type, handler, false);
} else {
element.attachEvent('on'+type, handler); // for IE6,7,8
}
}
function invertColor() {
var canvas = document.getElementById("target");
var len = canvas.width * canvas.height * 4;
var canvasData = tempContext.getImageData(0, 0, canvas.width, canvas.height);
var binaryData = canvasData.data;
// Processing all the pixels
gfilter.colorInvertProcess(binaryData, len);
// Copying back canvas data to canvas
tempContext.putImageData(canvasData, 0, 0);
}
function adjustColor() {
var canvas = document.getElementById("target");
var len = canvas.width * canvas.height * 4;
var canvasData = tempContext.getImageData(0, 0, canvas.width, canvas.height);
var binaryData = canvasData.data;
// Processing all the pixels
gfilter.colorAdjustProcess(binaryData, len);
// Copying back canvas data to canvas
tempContext.putImageData(canvasData, 0, 0);
}
function blurImage()
{
var canvas = document.getElementById("target");
var len = canvas.width * canvas.height * 4;
var canvasData = tempContext.getImageData(0, 0, canvas.width, canvas.height);
// Processing all the pixels
gfilter.blurProcess(tempContext, canvasData);
// Copying back canvas data to canvas
tempContext.putImageData(canvasData, 0, 0);
}
function fudiaoImage()
{
var canvas = document.getElementById("target");
var len = canvas.width * canvas.height * 4;
var canvasData = tempContext.getImageData(0, 0, canvas.width, canvas.height);
// Processing all the pixels
gfilter.reliefProcess(tempContext, canvasData);
// Copying back canvas data to canvas
tempContext.putImageData(canvasData, 0, 0);
}
function kediaoImage()
{
var canvas = document.getElementById("target");
var len = canvas.width * canvas.height * 4;
var canvasData = tempContext.getImageData(0, 0, canvas.width, canvas.height);
// Processing all the pixels
gfilter.diaokeProcess(tempContext, canvasData);
// Copying back canvas data to canvas
tempContext.putImageData(canvasData, 0, 0);
}
function mirrorImage()
{
var canvas = document.getElementById("target");
var len = canvas.width * canvas.height * 4;
var canvasData = tempContext.getImageData(0, 0, canvas.width, canvas.height);
// Processing all the pixels
gfilter.mirrorProcess(tempContext, canvasData);
// Copying back canvas data to canvas
tempContext.putImageData(canvasData, 0, 0);
}
滤镜源代码(gloomyfishfilter.js)：
var gfilter = {
type: "canvas",
name: "filters",
author: "zhigang",
getInfo: function () {
return this.author + ' ' + this.type + ' ' + this.name;
},
/**
* invert color value of pixel, new pixel = RGB(255-r, 255-g, 255 - b)
*
* @param binaryData - canvas's imagedata.data
* @param l - length of data (width * height of image data)
*/
colorInvertProcess: function(binaryData, l) {
for (var i = 0; i < l; i += 4) {
var r = binaryData[i];
var g = binaryData[i + 1];
var b = binaryData[i + 2];
binaryData[i] = 255-r;
binaryData[i + 1] = 255-g;
binaryData[i + 2] = 255-b;
}
},
/**
* adjust color values and make it more darker and gray...
*
* @param binaryData
* @param l
*/
colorAdjustProcess: function(binaryData, l) {
for (var i = 0; i < l; i += 4) {
var r = binaryData[i];
var g = binaryData[i + 1];
var b = binaryData[i + 2];
binaryData[i] = (r * 0.272) + (g * 0.534) + (b * 0.131);
binaryData[i + 1] = (r * 0.349) + (g * 0.686) + (b * 0.168);
binaryData[i + 2] = (r * 0.393) + (g * 0.769) + (b * 0.189);
}
},
/**
* deep clone image data of canvas
*
* @param context
* @param src
* @returns
*/
copyImageData: function(context, src)
{
var dst = context.createImageData(src.width, src.height);
dst.data.set(src.data);
return dst;
},
/**
* convolution - keneral size 5*5 - blur effect filter(模糊效果)
*
* @param context
* @param canvasData
*/
blurProcess: function(context, canvasData) {
console.log("Canvas Filter - blur process");
var tempCanvasData = this.copyImageData(context, canvasData);
var sumred = 0.0, sumgreen = 0.0, sumblue = 0.0;
for ( var x = 0; x < tempCanvasData.width; x++) {
for ( var y = 0; y < tempCanvasData.height; y++) {
// Index of the pixel in the array
var idx = (x + y * tempCanvasData.width) * 4;
for(var subCol=-2; subCol<=2; subCol++) {
var colOff = subCol + x;
if(colOff <0 || colOff >= tempCanvasData.width) {
colOff = 0;
}
for(var subRow=-2; subRow<=2; subRow++) {
var rowOff = subRow + y;
if(rowOff < 0 || rowOff >= tempCanvasData.height) {
rowOff = 0;
}
var idx2 = (colOff + rowOff * tempCanvasData.width) * 4;
var r = tempCanvasData.data[idx2 + 0];
var g = tempCanvasData.data[idx2 + 1];
var b = tempCanvasData.data[idx2 + 2];
sumred += r;
sumgreen += g;
sumblue += b;
}
}
// calculate new RGB value
var nr = (sumred / 25.0);
var ng = (sumgreen / 25.0);
var nb = (sumblue / 25.0);
// clear previous for next pixel point
sumred = 0.0;
sumgreen = 0.0;
sumblue = 0.0;
// assign new pixel value
canvasData.data[idx + 0] = nr; // Red channel
canvasData.data[idx + 1] = ng; // Green channel
canvasData.data[idx + 2] = nb; // Blue channel
canvasData.data[idx + 3] = 255; // Alpha channel
}
}
},
/**
* after pixel value - before pixel value + 128
* 浮雕效果
*/
reliefProcess: function(context, canvasData) {
console.log("Canvas Filter - relief process");
var tempCanvasData = this.copyImageData(context, canvasData);
for ( var x = 1; x < tempCanvasData.width-1; x++)
{
for ( var y = 1; y < tempCanvasData.height-1; y++)
{
// Index of the pixel in the array
var idx = (x + y * tempCanvasData.width) * 4;
var bidx = ((x-1) + y * tempCanvasData.width) * 4;
var aidx = ((x+1) + y * tempCanvasData.width) * 4;
// calculate new RGB value
var nr = tempCanvasData.data[aidx + 0] - tempCanvasData.data[bidx + 0] + 128;
var ng = tempCanvasData.data[aidx + 1] - tempCanvasData.data[bidx + 1] + 128;
var nb = tempCanvasData.data[aidx + 2] - tempCanvasData.data[bidx + 2] + 128;
nr = (nr < 0) ? 0 : ((nr >255) ? 255 : nr);
ng = (ng < 0) ? 0 : ((ng >255) ? 255 : ng);
nb = (nb < 0) ? 0 : ((nb >255) ? 255 : nb);
// assign new pixel value
canvasData.data[idx + 0] = nr; // Red channel
canvasData.data[idx + 1] = ng; // Green channel
canvasData.data[idx + 2] = nb; // Blue channel
canvasData.data[idx + 3] = 255; // Alpha channel
}
}
},
/**
* before pixel value - after pixel value + 128
* 雕刻效果
*
* @param canvasData
*/
diaokeProcess: function(context, canvasData) {
console.log("Canvas Filter - process");
var tempCanvasData = this.copyImageData(context, canvasData);
for ( var x = 1; x < tempCanvasData.width-1; x++)
{
for ( var y = 1; y < tempCanvasData.height-1; y++)
{
// Index of the pixel in the array
var idx = (x + y * tempCanvasData.width) * 4;
var bidx = ((x-1) + y * tempCanvasData.width) * 4;
var aidx = ((x+1) + y * tempCanvasData.width) * 4;
// calculate new RGB value
var nr = tempCanvasData.data[bidx + 0] - tempCanvasData.data[aidx + 0] + 128;
var ng = tempCanvasData.data[bidx + 1] - tempCanvasData.data[aidx + 1] + 128;
var nb = tempCanvasData.data[bidx + 2] - tempCanvasData.data[aidx + 2] + 128;
nr = (nr < 0) ? 0 : ((nr >255) ? 255 : nr);
ng = (ng < 0) ? 0 : ((ng >255) ? 255 : ng);
nb = (nb < 0) ? 0 : ((nb >255) ? 255 : nb);
// assign new pixel value
canvasData.data[idx + 0] = nr; // Red channel
canvasData.data[idx + 1] = ng; // Green channel
canvasData.data[idx + 2] = nb; // Blue channel
canvasData.data[idx + 3] = 255; // Alpha channel
}
}
},
/**
* mirror reflect
*
* @param context
* @param canvasData
*/
mirrorProcess : function(context, canvasData) {
console.log("Canvas Filter - process");
var tempCanvasData = this.copyImageData(context, canvasData);
for ( var x = 0; x < tempCanvasData.width; x++) // column
{
for ( var y = 0; y < tempCanvasData.height; y++) // row
{
// Index of the pixel in the array
var idx = (x + y * tempCanvasData.width) * 4;
var midx = (((tempCanvasData.width -1) - x) + y * tempCanvasData.width) * 4;
// assign new pixel value
canvasData.data[midx + 0] = tempCanvasData.data[idx + 0]; // Red channel
canvasData.data[midx + 1] = tempCanvasData.data[idx + 1]; ; // Green channel
canvasData.data[midx + 2] = tempCanvasData.data[idx + 2]; ; // Blue channel
canvasData.data[midx + 3] = 255; // Alpha channel
}
}
},
};
