站長資訊網(wǎng)在顯示馬賽克圖像時，淡入動畫是逐漸從很模糊到很清晰馬賽克的過程，淡出動畫的處理是從圖像變得清晰后又慢慢變得模糊的過程，下面我們就來看看具體的內(nèi)容。
我們先來看看馬賽克圖像的淡入效果
代碼如下
<!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>
說明：
由于body標(biāo)簽的onload事件，在頁面顯示時會通過調(diào)用loadImagen（）函數(shù)開始處理。
頁面顯示后創(chuàng)建內(nèi)部繪制的Canves對象，并讀取圖像。獲得繪制后的像素?cái)?shù)據(jù)。之后，啟動計(jì)時器處理，在計(jì)時器的事件中創(chuàng)建馬賽克圖像并將其繪制到畫面上。在執(zhí)行計(jì)時器處理時，會減少馬賽克的大小（fadeMosaicSize），從很粗的馬賽克開始變得很清晰的馬賽克動畫，以表示淡入效果。
要調(diào)整漸變速度，可以更改計(jì)時器的間隔，
fadeMosaicSize = Math.floor(fadeMosaicSize / 1.5);
運(yùn)行結(jié)果：
顯示上面的HTML文件。顯示很深的馬賽克圖像。
這是一個動態(tài)的過程，圖像會慢慢的變清晰，最后就會出現(xiàn)如下效果
看完了淡入的效果，接下來我們來看看馬賽克圖像淡入淡出的效果實(shí)現(xiàn)
代碼如下
<!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>
說明：
在處理完前一個代碼之后，它執(zhí)行2秒的間隔，然后在該間隔中執(zhí)行onFadeOut，是淡出之前執(zhí)行的代碼。
運(yùn)行結(jié)果
執(zhí)行上面的HTML文件，將顯示如下馬賽克效果
然后逐漸變得清晰，如下
之后，圖像顯示約兩秒鐘，然后圖像開始出現(xiàn)馬賽克效果，如下圖所示
然后，馬賽克逐漸變粗，最后隱藏，如下所示，頁面什么也沒有了
