纯JavaScript实现HTML5 Canvas六种特效滤镜

简介: 纯JavaScript实现HTML5 Canvas六种特效滤镜

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    
            }
    }
  },
};

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