纯JS实现HTML5 Canvas 6种特效滤镜

2020年7月9日 229点热度 0人点赞 0条评论

（给前端速报加星标，提升前端技能）

来源：

https://www.kancloud.cn/digest/canvas-programming/154008

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 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                }    }  },};