站长资讯网在显示马赛克图像时，淡入动画是逐渐从很模糊到很清晰马赛克的过程，淡出动画的处理是从图像变得清晰后又慢慢变得模糊的过程，下面我们就来看看具体的内容。
我们先来看看马赛克图像的淡入效果
代码如下
<!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title></title> <meta charset="utf-8" /> <script type="text/javascript"> var imageData; var fadeMosaicSize = 0; var THandle; var mem_canvas; var mem_context; var context; var img; function loadImage() { img = new Image(); mem_canvas = document.createElement('canvas'); img.onload = function onImageLoad() { mem_canvas.width = img.width; mem_canvas.height = img.height; mem_context = mem_canvas.getContext('2d'); mem_context.drawImage(img, 0, 0); imageData = mem_context.getImageData(0, 0, mem_canvas.width, mem_canvas.height); startFadeIn(); } img.src = 'img/luffy.jpg'; var canvas = document.getElementById('SimpleCanvas'); if (!canvas || !canvas.getContext) { return false; }else{ context = canvas.getContext('2d'); } } function startFadeIn() { fadeMosaicSize = 64; THandle = setInterval(onFadeIn, 50); } function onFadeIn() { if (fadeMosaicSize <= 1) { clearInterval(THandle); context.drawImage(img, 32, 32); } else { CreateMosaic(mem_context, mem_canvas.width, mem_canvas.height, fadeMosaicSize); context.drawImage(mem_canvas, 32, 32); fadeMosaicSize = Math.floor(fadeMosaicSize / 1.5); } } function CreateMosaic(context, width,height,mosaicSize) { var x=0; var y=0; for (y = 0; y < height; y = y + mosaicSize) { for (x = 0; x < width; x = x + mosaicSize) { var cR = imageData.data[(y * width + x) * 4]; var cG = imageData.data[(y * width + x) * 4 + 1]; var cB = imageData.data[(y * width + x) * 4 + 2]; context.fillStyle = "rgb("+cR+","+cG+","+cB+")"; context.fillRect(x, y, x + mosaicSize, y + mosaicSize); } } } </script> </head> <body onload="loadImage();" style="background-color:#D0D0D0;"> <canvas id="SimpleCanvas" width="640" height="360" style="background-color:#FFFFFF;"></canvas> <div>Canvas Demo</div> <div id="output"></div> </body> </html>
说明：
由于body标签的onload事件，在页面显示时会通过调用loadImagen（）函数开始处理。
页面显示后创建内部绘制的Canves对象，并读取图像。获得绘制后的像素数据。之后，启动计时器处理，在计时器的事件中创建马赛克图像并将其绘制到画面上。在执行计时器处理时，会减少马赛克的大小（fadeMosaicSize），从很粗的马赛克开始变得很清晰的马赛克动画，以表示淡入效果。
要调整渐变速度，可以更改计时器的间隔，
fadeMosaicSize = Math.floor(fadeMosaicSize / 1.5);
运行结果：
显示上面的HTML文件。显示很深的马赛克图像。
这是一个动态的过程，图像会慢慢的变清晰，最后就会出现如下效果
看完了淡入的效果，接下来我们来看看马赛克图像淡入淡出的效果实现
代码如下
<!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title></title> <meta charset="utf-8" /> <script type="text/javascript"> var imageData; var fadeMosaicSize = 0; var THandle; var mem_canvas; var mem_context; var context; var img; function loadImage() { img = new Image(); mem_canvas = document.createElement('canvas'); img.onload = function onImageLoad() { mem_canvas.width = img.width; mem_canvas.height = img.height; mem_context = mem_canvas.getContext('2d'); mem_context.drawImage(img, 0, 0); imageData = mem_context.getImageData(0, 0, mem_canvas.width, mem_canvas.height); startFadeIn(); } img.src = 'img/luffy.jpg'; var canvas = document.getElementById('SimpleCanvas'); if (!canvas || !canvas.getContext) { return false; }else{ context = canvas.getContext('2d'); } } function startFadeIn() { fadeMosaicSize = 64; THandle = setInterval(onFadeIn, 50); } function startFadeOut() { fadeMosaicSize = 1; THandle = setInterval(onFadeOut, 50); } function onFadeIn() { if (fadeMosaicSize <= 1) { clearInterval(THandle); context.drawImage(img, 32, 32); THandle = setInterval(onShow, 2000); } else { CreateMosaic(mem_context, mem_canvas.width, mem_canvas.height, fadeMosaicSize); context.drawImage(mem_canvas, 32, 32); fadeMosaicSize = Math.floor(fadeMosaicSize / 1.5); } } function onShow() { clearInterval(THandle); startFadeOut(); } function onFadeOut() { if (64 < fadeMosaicSize) { clearInterval(THandle); context.fillStyle = "#FFFFFF"; context.fillRect(32, 32, mem_canvas.width, mem_canvas.height); } else { CreateMosaic(mem_context, mem_canvas.width, mem_canvas.height, fadeMosaicSize); context.drawImage(mem_canvas, 32, 32); fadeMosaicSize = Math.ceil(fadeMosaicSize * 1.5); } } function CreateMosaic(context, width,height,mosaicSize) { var x=0; var y=0; for (y = 0; y < height; y = y + mosaicSize) { for (x = 0; x < width; x = x + mosaicSize) { var cR = imageData.data[(y * width + x) * 4]; var cG = imageData.data[(y * width + x) * 4 + 1]; var cB = imageData.data[(y * width + x) * 4 + 2]; context.fillStyle = "rgb("+cR+","+cG+","+cB+")"; context.fillRect(x, y, x + mosaicSize, y + mosaicSize); } } } </script> </head> <body onload="loadImage();" style="background-color:#D0D0D0;"> <canvas id="SimpleCanvas" width="640" height="360" style="background-color:#FFFFFF;"></canvas> <div>Canvas Demo</div> <div id="output"></div> </body> </html>
说明：
在处理完前一个代码之后，它执行2秒的间隔，然后在该间隔中执行onFadeOut，是淡出之前执行的代码。
运行结果
执行上面的HTML文件，将显示如下马赛克效果
然后逐渐变得清晰，如下
之后，图像显示约两秒钟，然后图像开始出现马赛克效果，如下图所示
然后，马赛克逐渐变粗，最后隐藏，如下所示，页面什么也没有了
