编程 Javascript

纯JavaScript实现HTML5 Canvas六种特效滤镜示例

Posted in Javascript onJune 28, 2013

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 
} 
} 
}, 
};

纯JavaScript实现HTML5 Canvas六种特效滤镜示例

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