前端
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.合理
滤镜原理解释：
2.灰色调：获取一个预期点rgb值r，g，b则新的rgb值
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：
根据当前预期的前一个预期rgb值与它的后一个重新的rgb值之差再加上128
5.总体：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、如何添加一个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对象中获取预定数据
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;4、如何对dom对象实现鼠标clickevent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 api6、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
}
}
},
};
