本文作者html5tricks，转载请注明出处
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
HTML代码如下
Change pixel resolution 32
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
* /resources/close-pixelate/
*
* Developed by
* - David DeSandro
* - John Schulz /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。
