纯JavaScript实现HTML5 Canvas六种特效滤镜
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 } } }, };
