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POhtml5 remove from canvas
 

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    <p>This is my first html5 project, getting the gist of it, need a bit of help. I used a jquery UI slider to send an opacity value to the canvas and it works quite nicely... but I can't get the image to completely turn off when the slider is in the off position with a value of zero. Here is a fiddle of what I'm trying to do : <a href="http://jsfiddle.net/N6wZZ/2/" rel="nofollow">http://jsfiddle.net/N6wZZ/2/</a></p> <p>Here is my JS:</p> <pre><code>$("#slider").slider({ animate: true, range: "min", value: 0, min: 0, max: 0.9, step: .01, create: function (event, ui) { var opacityValue = '0.0'; canvasFunction(opacityValue); }, slide: function (event, ui) { $('#hiddenField').attr('value', ui.value); $("#slider-result").html(ui.value); var opacityValue = $('#hiddenField').val(); if (opacityValue == 0) { var opacityValue = 0; var workAroundVar = 300; var workAroundVarTwo = 0; canvasFunction(opacityValue, workAroundVar, workAroundVarTwo); } else { var workAroundVar = 0; var workAroundVarTwo = 300; canvasFunction(opacityValue, workAroundVar, workAroundVarTwo); } } }); function canvasFunction(opacityValue, workAroundVar, workAroundVarTwo){ var canvas = document.getElementById("myCanvas"); var ctx = canvas.getContext("2d"); var img1 = loadImage('http://moosepic.com/test2.png', main); var img2 = loadImage('http://moosepic.com/test.png', main); var imagesLoaded = 0; function main() { imagesLoaded += 1; if (imagesLoaded == 2) { // composite now ctx.drawImage(img1, 0, 0, 300, 300); ctx.globalAlpha = opacityValue; ctx.drawImage(img2, workAroundVar, workAroundVar, workAroundVarTwo, workAroundVarTwo); } } function loadImage(src, onload) { var img = new Image(); img.onload = onload; img.src = src; return img; } } </code></pre> <p>as you can see I've made a bunch of workarounds to turn off the second image or just knock it out of the canvas. Any help would be awesome. </p>
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    1. COWhen you're drawing the canvas the very first time, what are workAroundVar 1 and 2 set to? I see them blank.
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      1. USRutwick Gangurde
    2. COthis is happening because your code's overall logic is wrong. do not load the images every time the slider moves, load them once and then just redraw the canvas. get rid of your workaround variables. they are wrong too.
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      1. USakonsu
    3. CO@akonsu But loading the image is redraw right?
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      1. USRutwick Gangurde
 

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