canvas saving as image not working on mobile devices

Question

i have a code that combines multiple canvasses and saves them into one image file. while this works on non-mobile devices, i tested it on a mobile device and while there is an image produced, opening the file will give you a message that says that "The image _ cannot be displayed because it contains errors."

Here's the code that converts to image:

<script type='text/javascript'>
window.addEventListener('load', function() {
    'use strict';
    var src = document.getElementById('src');
    var dst = document.getElementById('dst');
    var dst1 = document.getElementById('dst1');
    var input = src.getContext('2d');
    var output = dst.getContext('2d');
    var output1 = dst1.getContext('2d');

    dst.width = dst_w;
    dst.height = dst_h;
    dst1.width = dst1_w;
    dst1.height = dst1_h;

    var img=document.getElementById("scream");
    input.drawImage(img,0,0);

    var sprkl = document.getElementById('sprkl');
    var output_s = sprkl.getContext('2d');
    input.drawImage(document.getElementById('sparkle'),0,0,150,150);

    input.drawImage(document.getElementById('circle'),0,0,<?php echo $lenssize.",".$lenssize.",".$left.",".$top.",".$dia.",".$dia; ?>);
    input.drawImage(document.getElementById('circle1'),0,0,<?php echo $lenssize.",".$lenssize.",".$left1.",".$top1.",".$dia1.",".$dia1; ?>);

    function gonext() {
    var a = document.getElementById('src');
    var dataURL = a.toDataURL();
    $.post("save.php?filen=<?php echo $filen; ?>", {data: a.toDataURL("image/png")})
    window.setTimeout(function() {
            document.frmnext.submit();
    }, 10000);
}

<div style="position: relative; z-index: 2">
            <canvas id="src" width="<?php echo $width; ?>" height="<?php echo $height; ?>"></canvas>
            <canvas id="sprkl" style="position: absolute; z-index: 3;"></canvas>
            <canvas id="dst" style='position: absolute; z-index: 3'></canvas>
            <canvas id="dst1" style='position: absolute; z-index: 3'></canvas>
</div>

Answer 1

To support toDataURL try this because i think, there is a problem with export image with data string like base64 ...

I had same problem with my project, and i found this solution

$('.jSignature').attr('id','image_b_id');
var canvas_1 = document.getElementById('image_b_id');
var image_b_base64 = canvas_1.toDataURL();

When i create jSignature Canvas , i could run in many of mobile devices. But there is an error some the other devices such as Galaxy mini ...

Answer 2

I really appreciate your time in replying to my problem, however the solution I've found is here

I simply added the js file and that was it.

Thanks again :)