HTML5 Canvas图片马赛克模糊动画

布满荆棘的人生 2022-07-30 13:12 231阅读 0赞

经常可以在网上或者电视上看到被马赛克模糊的图片或者视频，今天我们要利用[HTML5][] Canvas技术来实现图片的马赛克模糊效果。在演示中我们可以拖动滑竿来设置马赛克模糊的程度，你可以在不同的值下观察图片被马赛克后的效果。HTML5的确非常强大。

[![html5-canvas-image-mosaics][]][html5-canvas-image-mosaics 1]

## HTML代码如下 ##

定义了一个滑竿和3张待模糊的图片。

## JavaScript代码如下 ##

/*!
     * Close Pixelate v2.0.00 beta
     * http://desandro.com/resources/close-pixelate/
     * 
     * Developed by
     * - David DeSandro  http://desandro.com
     * - John Schulz  http://twitter.com/jfsiii
     * 
     * Licensed under MIT license
     */
    
    /*jshint asi: true, browser: true, eqeqeq: true, forin: false, immed: false, newcap: true, noempty: true, strict: true, undef: true */
    
    ( function( window, undefined ) {
    
    //
    'use strict';
    
    // util vars
    var TWO_PI = Math.PI * 2
    var QUARTER_PI = Math.PI * 0.25
    
    // utility functions
    function isArray( obj ) {
      return Object.prototype.toString.call( obj ) === "[object Array]"
    }
    
    function isObject( obj ) {
      return Object.prototype.toString.call( obj ) === "[object Object]"
    }
    
    var console = window.console
    
    // check for canvas support
    var canvas = document.createElement('canvas')
    var isCanvasSupported = canvas.getContext && canvas.getContext('2d')
    
    // don't proceed if canvas is no supported
    if ( !isCanvasSupported ) {
      return
    }
    
    function ClosePixelation( img, options ) {
      this.img = img
      // creat canvas
      var canvas = this.canvas = document.createElement('canvas')
      this.ctx = canvas.getContext('2d')
      // copy attributes from img to canvas
      canvas.className = img.className
      canvas.id = img.id
    
      this.render( options )
    
      // replace image with canvas
      img.parentNode.replaceChild( canvas, img )
    
    }
    
    ClosePixelation.prototype.render = function( options ) {
      this.options = options
      // set size
      var w = this.width = this.canvas.width = this.img.width
      var h = this.height = this.canvas.height = this.img.height
      // draw image on canvas
      this.ctx.drawImage( this.img, 0, 0 )
      // get imageData
    
      try {
        this.imgData = this.ctx.getImageData( 0, 0, w, h ).data
      } catch ( error ) {
        if ( console ) {
          console.error( error )
        }
        return
      }
    
      this.ctx.clearRect( 0, 0, w, h )
    
      for ( var i=0, len = options.length; i < len; i++ ) {
        this.renderClosePixels( options[i] )
      }
    
    }
    
    ClosePixelation.prototype.renderClosePixels = function( opts ) {
      var w = this.width
      var h = this.height
      var ctx = this.ctx
      var imgData = this.imgData
    
      // option defaults
      var res = opts.resolution || 16
      var size = opts.size || res
      var alpha = opts.alpha || 1
      var offset = opts.offset || 0
      var offsetX = 0
      var offsetY = 0
      var cols = w / res + 1
      var rows = h / res + 1
      var halfSize = size / 2
      var diamondSize = size / Math.SQRT2
      var halfDiamondSize = diamondSize / 2
    
      if ( isObject( offset ) ){ 
        offsetX = offset.x || 0
        offsetY = offset.y || 0
      } else if ( isArray( offset) ){
        offsetX = offset[0] || 0
        offsetY = offset[1] || 0
      } else {
        offsetX = offsetY = offset
      }
    
      var row, col, x, y, pixelY, pixelX, pixelIndex, red, green, blue, pixelAlpha
    
      for ( row = 0; row < rows; row++ ) {
        y = ( row - 0.5 ) * res + offsetY
        // normalize y so shapes around edges get color
        pixelY = Math.max( Math.min( y, h-1), 0)
    
        for ( col = 0; col < cols; col++ ) {
          x = ( col - 0.5 ) * res + offsetX
          // normalize y so shapes around edges get color
          pixelX = Math.max( Math.min( x, w-1), 0)
          pixelIndex = ( pixelX + pixelY * w ) * 4
          red   = imgData[ pixelIndex + 0 ]
          green = imgData[ pixelIndex + 1 ]
          blue  = imgData[ pixelIndex + 2 ]
          pixelAlpha = alpha * ( imgData[ pixelIndex + 3 ] / 255)
    
          ctx.fillStyle = 'rgba(' + red +','+ green +','+ blue +','+ pixelAlpha + ')'
    
          switch ( opts.shape ) {
            case 'circle' :
              ctx.beginPath()
                ctx.arc ( x, y, halfSize, 0, TWO_PI, true )
                ctx.fill()
              ctx.closePath()
              break
            case 'diamond' :
              ctx.save()
                ctx.translate( x, y )
                ctx.rotate( QUARTER_PI )
                ctx.fillRect( -halfDiamondSize, -halfDiamondSize, diamondSize, diamondSize )
              ctx.restore()
              break
            default :
              // square
              ctx.fillRect( x - halfSize, y - halfSize, size, size )
          } // switch
        } // col
      } // row
    
    }
    
    // enable img.closePixelate
    HTMLImageElement.prototype.closePixelate = function ( options ) {
      return new ClosePixelation( this, options )
    }
    
    // put in global namespace
    window.ClosePixelation = ClosePixelation
    
    })( window );

以上这个JS文件是马赛克模糊效果的具体实现。

下面是页面上调用的JS代码：

var dolly1 = document.getElementById('dolly1')
    	  var dolly2 = document.getElementById('dolly2')
    	  var dolly3 = document.getElementById('dolly3')
    	  var pixelOpts = [ { resolution: 8 } ]
    	  var pixelDolly1 = dolly1.closePixelate( pixelOpts )
    	  var pixelDolly2 = dolly2.closePixelate( pixelOpts )
    	  var pixelDolly3 = dolly3.closePixelate( pixelOpts )
    	  var range = document.getElementById('range')
    	  var output = document.getElementById('output')
    
    	  range.addEventListener( 'change', function( event ) {
    	    var res = parseInt( event.target.value, 10 )
    	    res = Math.floor( res / 2 ) * 2
    	    res = Math.max( 4, Math.min( 100, res ) )
    	    output.textContent = res
    	    // console.log( res );
    	    pixelOpts = [ { resolution: res } ]
    	    pixelDolly1.render( pixelOpts )
    	    pixelDolly2.render( pixelOpts )
    	    pixelDolly3.render( pixelOpts )
    	  }, false )

以上就是实现这款HTML5 Canvas图片马赛克模糊动画的全部过程。

来源：http://www.html5tricks.com/html5-canvas-image-mosaics.html       
来个实例：http://qmzg.qq.com/cp/a20150604qmzg/

[HTML5]: http://www.html5tricks.com/
[html5-canvas-image-mosaics]: /images/20220724/ce164e7f128d4b80ab6f0cec6d07d96b.png
[html5-canvas-image-mosaics 1]: http://www.html5tricks.com/demo/html5-canvas-image-mosaics/index.html