Question

好的，我要做的是使用下面的示例制作幻灯片。问题是动画不起作用。设计明智它看起来不错，但图像不会在我的浏览器中旋转。是因为我必须使用window.setTimeout（）谢谢！

http://tutorialzine.com/2010/09/html5-canvas-slideshow-jquery/

也有人似乎遇到了类似的问题但与我的代码不完全相同：

继承人HTML：

<!DOCTYPE html>
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>An HTML5 Slideshow w/ Canvas & jQuery | Tutorialzine Demo</title>

    <link rel="stylesheet" type="text/css" href="styles.css" />

    </head>

    <body>

    <div id="slideshow">

        <ul class="slides">
            <li><img src="img/photos/1.jpg" width="620" height="320" alt="Marsa Alam" /></li>
            <li><img src="img/photos/2.jpg" width="620" height="320" alt="Turrimetta Beach" /></li>
            <li><img src="img/photos/3.jpg" width="620" height="320" alt="Power Station" /></li>
            <li><img src="img/photos/4.jpg" width="620" height="320" alt="Colors of Nature" /></li>
        </ul>

        <span class="arrow previous"></span>
        <span class="arrow next"></span>
    </div>

    <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
    <script src="script.js"></script>
    </body>
    </html>

然后我们有CSS：

#slideshow{
    background-color:#F5F5F5;
    border:1px solid #FFFFFF;
    height:340px;
    margin:150px auto 0;
    position:relative;
    width:640px;

    -moz-box-shadow:0 0 22px #111;
    -webkit-box-shadow:0 0 22px #111;
    box-shadow:0 0 22px #111;
}

#slideshow ul{
    height:320px;
    left:10px;
    list-style:none outside none;
    overflow:hidden;
    position:absolute;
    top:10px;
    width:620px;
}

#slideshow li{
    position:absolute;
    display:none;
    z-index:10;
}

#slideshow li:first-child{
    display:block;
    z-index:1000;
}

#slideshow .slideActive{
    z-index:1000;
}

#slideshow canvas{
    display:none;
    position:absolute;
    z-index:100;
}

#slideshow .arrow{
    height:86px;
    width:60px;
    position:absolute;
    background:url('img/arrows.png') no-repeat;
    top:50%;
    margin-top:-43px;
    cursor:pointer;
    z-index:5000;
}

#slideshow .previous{ background-position:left top;left:0;}
#slideshow .previous:hover{ background-position:left bottom;}

#slideshow .next{ background-position:right top;right:0;}
#slideshow .next:hover{ background-position:right bottom;}

现在javascript：

$(window).load(function(){

    // We are listening to the window.load event, so we can be sure
    // that the images in the slideshow are loaded properly.

    // Testing wether the current browser supports the canvas element:
    var supportCanvas = 'getContext' in document.createElement('canvas');

    // The canvas manipulations of the images are CPU intensive,
    // this is why we are using setTimeout to make them asynchronous
    // and improve the responsiveness of the page.

    var slides = $('#slideshow li'),
        current = 0,
        slideshow = {width:0,height:0};

    setTimeout(function(){

        if(supportCanvas){
            $('#slideshow img').each(function(){

                if(!slideshow.width){
                    // Saving the dimensions of the first image:
                    slideshow.width = this.width;
                    slideshow.height = this.height;
                }

                // Rendering the modified versions of the images:
                createCanvasOverlay(this);
            });
        }

        $('#slideshow .arrow').click(function(){
            var li            = slides.eq(current),
                canvas        = li.find('canvas'),
                nextIndex    = 0;

            // Depending on whether this is the next or previous
            // arrow, calculate the index of the next slide accordingly.

            if($(this).hasClass('next')){
                nextIndex = current >= slides.length-1 ? 0 : current+1;
            }
            else {
                nextIndex = current <= 0 ? slides.length-1 : current-1;
            }

            var next = slides.eq(nextIndex);

            if(supportCanvas){

                // This browser supports canvas, fade it into view:

                canvas.fadeIn(function(){

                    // Show the next slide below the current one:
                    next.show();
                    current = nextIndex;

                    // Fade the current slide out of view:
                    li.fadeOut(function(){
                        li.removeClass('slideActive');
                        canvas.hide();
                        next.addClass('slideActive');
                    });
                });
            }
            else {

                // This browser does not support canvas.
                // Use the plain version of the slideshow.

                current=nextIndex;
                next.addClass('slideActive').show();
                li.removeClass('slideActive').hide();
            }
        });

    },100);

// This function takes an image and renders
    // a version of it similar to the Overlay blending
    // mode in Photoshop.

    function createCanvasOverlay(image){

        var canvas            = document.createElement('canvas'),
            canvasContext    = canvas.getContext("2d");

        // Make it the same size as the image
        canvas.width = slideshow.width;
        canvas.height = slideshow.height;

        // Drawing the default version of the image on the canvas:
        canvasContext.drawImage(image,0,0);

        // Taking the image data and storing it in the imageData array:
        var imageData    = canvasContext.getImageData(0,0,canvas.width,canvas.height),
            data        = imageData.data;

        // Loop through all the pixels in the imageData array, and modify
        // the red, green, and blue color values.

        for(var i = 0,z=data.length;i<z;i++){

            // The values for red, green and blue are consecutive elements
            // in the imageData array. We modify the three of them at once:

            data[i] = ((data[i] < 128) ? (2*data[i]*data[i] / 255) :
                        (255 - 2 * (255 - data[i]) * (255 - data[i]) / 255));
            data[++i] = ((data[i] < 128) ? (2*data[i]*data[i] / 255) :
                        (255 - 2 * (255 - data[i]) * (255 - data[i]) / 255));
            data[++i] = ((data[i] < 128) ? (2*data[i]*data[i] / 255) :
                        (255 - 2 * (255 - data[i]) * (255 - data[i]) / 255));

            // After the RGB channels comes the alpha value, which we leave the same.
            ++i;
        }

        // Putting the modified imageData back on the canvas.
        canvasContext.putImageData(imageData,0,0,0,0,imageData.width,imageData.height);

        // Inserting the canvas in the DOM, before the image:
        image.parentNode.insertBefore(canvas,image);
    }

});

Answer 1

仅供参考，谷歌的cnd目前处于关闭状态：http://www.websitedown.info/ajax.googleapis.com，因此可能无法加载jquery。

google's cnd results

为什么这个幻灯片不会起作用

1 个答案: