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HTML5 Canvas Slideshow

· Web Dev Zone

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In this tutorial we are making a HTML5 Slideshow (canvas) with its own animated transitioning effect. The main idea is: drawing images with higher contrast in the ends of transitions.

Here are our demo and downloadable packages:

Live Demo

download in package


Ok, download the source files and let's start coding !


Step 1. HTML

This is the markup of our resulting slideshow page.

index.html

<!DOCTYPE html>
<html lang="en" >
    <head>
        <meta charset="utf-8" />
        <title>HTML5 Canvas Slideshow | Script Tutorials</title>
        <link href="css/main.css" rel="stylesheet" type="text/css" />
        <script src="http://code.jquery.com/jquery-latest.min.js"></script>
        <script src="js/pixastic.custom.js"></script>
        <script src="js/script.js"></script>
    </head>
    <body>
        <header>
            <h2>HTML5 Canvas Slideshow</h2>
            <a href="http://www.script-tutorials.com/html5-canvas-slideshow/" class="stuts">Back to original tutorial on <span>Script Tutorials</span></a>
        </header>
        <div class="container">
            <div class="slides">
                <img src="images/pic1.jpg" />
                <img src="images/pic2.jpg" />
                <img src="images/pic3.jpg" />
                <img src="images/pic4.jpg" />
                <img src="images/pic5.jpg" />
                <img src="images/pic6.jpg" />
                <img src="images/pic7.jpg" />
            </div>
            <canvas id="slideshow" width="900" height="300"></canvas>
        </div>
    </body>
</html>

Step 2. CSS

Here are all the stylesheets:

css/main.css

/* page layout styles */
*{
    margin:0;
    padding:0;
}
body {
    background-color:#eee;
    color:#fff;
    font:14px/1.3 Arial,sans-serif;
}
header {
    background-color:#212121;
    box-shadow: 0 -1px 2px #111111;
    display:block;
    height:70px;
    position:relative;
    width:100%;
    z-index:100;
}
header h2{
    font-size:22px;
    font-weight:normal;
    left:50%;
    margin-left:-400px;
    padding:22px 0;
    position:absolute;
    width:540px;
}
header a.stuts,a.stuts:visited{
    border:none;
    text-decoration:none;
    color:#fcfcfc;
    font-size:14px;
    left:50%;
    line-height:31px;
    margin:23px 0 0 110px;
    position:absolute;
    top:0;
}
header .stuts span {
    font-size:22px;
    font-weight:bold;
    margin-left:5px;
}
.container {
    color: #000;
    margin: 20px auto;
    position: relative;
    width: 900px;
}
#slideshow {
    border:1px #000 solid;
    box-shadow:4px 6px 6px #444444;
    display:block;
    margin:0 auto;
    height:300px;
    width:900px;
}
.container .slides {
    display:none;
}

Step 3. JS

js/pixastic.custom.js

Pixastic – JavaScript Image Processing Library. I have used it to change the brightness and contrast of our canvas. You can download this library here. Or, you can find this library in our package too.

js/script.js

var canvas, ctx;
var aImages = [];
var iCurSlide = 0;
var iCnt = 0;
var iSmTimer = 0;
var iContr = 0;
var iEfIter = 50;

$(function(){
    // creating canvas objects
    canvas = document.getElementById('slideshow');
    ctx = canvas.getContext('2d');

    // collect all images
    $('.slides').children().each(function(i){
        var oImg = new Image();
        oImg.src = this.src;
        aImages.push(oImg);
    });

    // draw first image
    ctx.drawImage(aImages[iCurSlide], 0, 0);

    var iTimer = setInterval(changeSlideTimer, 5000); // set inner timer
});

function changeSlideTimer() {
    iCurSlide++;
    if (iCurSlide == $(aImages).length) {
        iCurSlide = 0;
    }

    clearInterval(iSmTimer);
    iSmTimer = setInterval(drawSwEffect, 40); // extra one timer
}

// draw switching effect
function drawSwEffect() {
    iCnt++;

    if (iCnt <= iEfIter / 2) {
        iContr += 0.004;

        // change brightness and contrast
        Pixastic.process(canvas, 'brightness',
            {
                'brightness': 2,
                'contrast': 0.0 + iContr,
                'leaveDOM': true
            },
            function(img) {
                ctx.drawImage(img, 0, 0);
            }
        );
    }

    if (iCnt > iEfIter / 2) {
        // change brightness
        Pixastic.process(canvas, 'brightness',
            {
                'brightness': -2,
                'contrast': 0,
                'leaveDOM': true
            },
            function(img) {
                ctx.drawImage(img, 0, 0);
            }
        );
    }

    if (iCnt == iEfIter / 2) { // switch actual image
        iContr = 0;
        ctx.drawImage(aImages[iCurSlide], 0, 0);

        Pixastic.process(canvas, 'brightness',
            {
                'brightness': iEfIter,
                'contrast': 0,
                'leaveDOM': true
            },
            function(img) {
                ctx.drawImage(img, 0, 0);
            }
        );
    } else if (iCnt == iEfIter) { // end of cycle, clear extra sub timer
        clearInterval(iSmTimer);
        iCnt = 0;
        iContr = 0;
    }
}

As you can see – the main functionality is easy. I have defined the main timer (which will change images), and one inner timer, which will change the brightness and contrast of our canvas.


Live Demo

download in package


Conclusion

I hope that today’s html5 slideshow lesson was interesting for you as always. We have made another nice html5 example. I will be glad to see your thanks and comments. Good luck!

 

Source: http://www.script-tutorials.com/html5-canvas-slideshow/

Learn why developers are gravitating towards Node and its ability to retain and leverage the skills of JavaScript developers and the ability to deliver projects faster than other languages can.  Brought to you in partnership with IBM.

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