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Cross-Browser Grayscale background image

Posted by admin at 8:59 日時 2014/03/31

This is a modified version of a tutorial “Cross-Browser Grayscale image example using CSS3 + JS“.

This original version worked well, but only for actual img objects. If you’d like to apply mouse over grayscale effect for background images, try modify functions.js like this:

if (getInternetExplorerVersion() >= 10){        $('.example ul').imagesLoaded(function(){  	    $('.example ul li').each(function(){  		// get background-image style value  	    	var backgroundImage = $(this).css('background-image');  		// get background-image src  	    	var backgroundImageSrc = backgroundImage.replace(/^url\(["']?/, '').replace(/["']?\)$/, '');  		// get grayscale data url  	    	var grayScaleImageSrc = grayscaleIE10(backgroundImageSrc);  		// set color image src to data attribute  	    	$(this).data('image-src', backgroundImageSrc);  		// set grayscale image src to data attribute  	    	$(this).data('grayscale-src', grayScaleImageSrc);  		// change grayscale to default  	    	this.style.backgroundImage = "url(" + grayScaleImageSrc + ")";  	    }).hover(function(){  		// change to the color image  	    	var src = $(this).data('image-src');  	    	this.style.backgroundImage = "url(" + src + ")";  	    }, function(){  		// change back to the grayscale image  	    	var src = $(this).data('grayscale-src');  	    	this.style.backgroundImage = "url(" + src + ")";  	    });  	});  		  	function grayscaleIE10(src){  		var canvas = document.createElement('canvas');  		var ctx = canvas.getContext('2d');  		var imgObj = new Image();  		imgObj.src = src;  		canvas.width = 300; // from your stylesheet  		canvas.height = 200; // from your stylesheet  		ctx.clearRect(0, 0, canvas.width, canvas.height);  		ctx.drawImage(imgObj, 0, 0);   		var imgPixels = ctx.getImageData(0, 0, canvas.width, canvas.height);  		for(var y = 0; y < imgPixels.height; y++){  			for(var x = 0; x < imgPixels.width; x++){  				var i = (y * 4) * imgPixels.width + x * 4;  				var avg = (imgPixels.data[i] + imgPixels.data[i + 1] + imgPixels.data[i + 2]) / 3;  				imgPixels.data[i] = avg;   				imgPixels.data[i + 1] = avg;   				imgPixels.data[i + 2] = avg;  			}  		}  		ctx.putImageData(imgPixels, 0, 0, 0, 0, imgPixels.width, imgPixels.height);  		return canvas.toDataURL();  	};  	  };

マウスオーバーするとグレイスケールの画像がカラーになる、という効果を実装するサンプル。リンク先のチュートリアルの通りにすればimgタグを使っている場合はうまくいくのですが、背景画像の場合、このIE10以降対応の部分が動きません。なのでちょいと変更してみたサンプルです。

Thanks to original blog post and wonderful tutorial!


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