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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4046;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 imagetempContext = 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

 //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：

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：

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 = tempCanvasData.width) {                    colOff = 0;                  }                  for(var subRow=-2; subRow= 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 255) ? 255 : nr);                ng = (ng 255) ? 255 : ng);                nb = (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 255) ? 255 : nr);                ng = (ng 255) ? 255 : ng);                nb = (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