Fading a loaded image into Canvas with drawImage - Javascript Canvas

Javascript examples for Canvas:image

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Description

Fading a loaded image into Canvas with drawImage

Demo Code

ResultView the demo in separate window 

<html>
   <head> 
      <meta name="viewport" content="width=device-width, initial-scale=1"> 
      <script type="text/javascript" src="https://code.jquery.com/jquery-1.9.1.js"></script> 
      <style id="compiled-css" type="text/css">

body {//from  ww w. ja  v a2 s .  c  om
   background-color: ivory;
}
canvas {
   border:1px solid red;
}


      </style> 
      <script type="text/javascript">
    $(window).load(function(){
$("#fade").hide();
var imageURLs = []; // put the paths to your images here
var imagesOK = 0;
var imgs = [];
imageURLs.push("https://www.java2s.com/style/demo/InternetExplorer.png");
imageURLs.push("https://www.java2s.com/style/demo/InternetExplorer.png");
imageURLs.push("https://www.java2s.com/style/demo/Safari.png");
imageURLs.push("https://www.java2s.com/style/demo/InternetExplorer.png");
loadAllImages();
//
function loadAllImages() {
    for (var i = 0; i < imageURLs.length; i++) {
        var img = new Image();
        imgs.push(img);
        img.onload = function () {
            imagesOK++;
            if (imagesOK >= imageURLs.length) {
                $("#fade").show();
                ctx.drawImage(imgs[0], 0, 0);
            }
        };
        img.onerror = function () {
            console.log("image load failed");
        }
        img.crossOrigin = "anonymous";
        img.src = imageURLs[i];
    }
}
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var fadeOutIndex = imgs.length - 1;
var fadeInIndex = 0;
var fadePct = 0;
function animateFade() {
    if (fadePct > 100) {
        return;
    }
    requestAnimationFrame(animateFade);
    //            ctx.clearRect(0,0,canvas.width,canvas.height);
    draw(imgs[fadeInIndex], fadePct / 100);
    draw(imgs[fadeOutIndex], (1 - fadePct / 100));
    fadePct++;
}
function draw(img, opacity) {
    ctx.save();
    ctx.globalAlpha = opacity;
    ctx.drawImage(img, 0, 0);
    ctx.restore();
}
$("#fade").click(function () {
    fadePct = 0;
    if (++fadeOutIndex == imgs.length) {
        fadeOutIndex = 0;
    }
    if (++fadeInIndex == imgs.length) {
        fadeInIndex = 0;
    }
    animateFade();
});
    });

      </script> 
   </head> 
   <body> 
      <button id="fade">Fade to next Image</button>
      <br> 
      <canvas id="canvas" width="204" height="204"></canvas>
      <br>  
   </body>
</html>

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