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Editorial Team
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Asked: 2026-05-30T15:21:01+00:00

I have the Java Script that would grey images automatically and fade up to

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I have the Java Script that would grey images automatically and fade up to colour on Mouse over !

i have added the code below to the header of my html page ! But it is’nt working i have tried changing the target images.

Is there anything to do in the HTML or CSS after adding this Code.

How should the the images be set to work

<script src="jquery.js" type="text/javascript"></script>
<script type="text/javascript">

// On window load. This waits until images have loaded which is essential
$(window).load(function(){

    // Fade in images so there isn't a color "pop" document load and then on window load
    $(".menu img").fadeIn(500);

    // clone image
    $('.menu img').each(function(){
        var el = $(this);
        el.css({"position":"absolute"}).wrap("<div class='img_wrapper' style='display: inline-block'>").clone().addClass('img_grayscale').css({"position":"absolute","z-index":"998","opacity":"0"}).insertBefore(el).queue(function(){
            var el = $(this);
            el.parent().css({"width":this.width,"height":this.height});
            el.dequeue();
        });
        this.src = grayscale(this.src);
    });

    // Fade image 
    $('.menu img').mouseover(function(){
        $(this).parent().find('img:first').stop().animate({opacity:1}, 1000);
    })
    $('.img_grayscale').mouseout(function(){
        $(this).stop().animate({opacity:0}, 1000);
    });     
});

// Grayscale w canvas method
function grayscale(src){
    var canvas = document.createElement('canvas');
    var ctx = canvas.getContext('2d');
    var imgObj = new Image();
    imgObj.src = src;
    canvas.width = imgObj.width;
    canvas.height = imgObj.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();
}

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1 Answer

  1. Editorial Team

    As you can see – it works perfectly http://jsfiddle.net/8aSmM/

    The problem may arise from:

    1. Your browser does not support canvas
    2. Your images are loading from another domain. Read this https://developer.mozilla.org/en/Canvas_tutorial/Using_images#Using_images_from_other_domains The image at the example above is from jsfiddle.

    Although you can use images without CORS approval in your canvas,
    doing so taints the canvas. Once a canvas has been tainted, you can no
    longer pull data back out of the canvas. For example, you can no
    longer use the canvas toBlob(), toDataURL(), or getImageData()
    methods; doing so will throw a security error.

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