HTML2canvas generates Blurry images

solution is very simple, after X hours of testing.

Set your ALL div's 2x higher, your IMG 2x higher, and finally set html zoom on 0.5, or if you want better quality yet, set 3x higher (in this case the html zoom must be 0.33) or more, (the original image sizes are assumed to be larger).

For example:

HTML

<body>
 <div class="pdf">
   <img src="image.jpg">
 </div>
</body>

CSS before

body {
    background: #b2b2b2;
}
.pdf {
   background: #fff;
   /* A4 size */
   width: 842px;
   height: 595px;
 }
img {
   width: 300px;
   height: 200px;
}

CSS after (only changes)

html {
   zoom: 0.5;
}

.pdf {
   /* A4 size before . 2 */
   width: 1684; 
   height: 1190px; 
 }
img { /* size before . 2 */
   width: 600px;
   height: 400px;
}

AND here is my result:

PDF before PDF after


I had this problem because I was on a retina display. I solved in by using MisterLamb's solution here.

$(window).load(function () {

    var scaleBy = 5;
    var w = 1000;
    var h = 1000;
    var div = document.querySelector('#screen');
    var canvas = document.createElement('canvas');
    canvas.width = w * scaleBy;
    canvas.height = h * scaleBy;
    canvas.style.width = w + 'px';
    canvas.style.height = h + 'px';
    var context = canvas.getContext('2d');
    context.scale(scaleBy, scaleBy);

    html2canvas(div, {
        canvas:canvas,
        onrendered: function (canvas) {
            theCanvas = canvas;
            document.body.appendChild(canvas);

            Canvas2Image.saveAsPNG(canvas);
            $(body).append(canvas);
        }
    });
});

HTML and PNG without scaling

enter image description here

HTML and PNG with scaling

enter image description here


you can use scale options in html2canvas.

In the latest release, v1.0.0-alpha.1, you can use the scale option to increase the resolution (scale: 2 will double the resolution from the default 96dpi).

// Create a canvas with double-resolution.
html2canvas(element, {
    scale: 2,
    onrendered: myRenderFunction
});
// Create a canvas with 144 dpi (1.5x resolution).
html2canvas(element, {
    dpi: 144,
    onrendered: myRenderFunction
});

I was facing this problem and i solved it by using domtoimage instead of html2canvas.

This HTML2CANVAS solution was not working good for me i know the scale option does increase the target div's size before capturing it but it won't work if you have something inside that div which won't resize e.g in my case it was canvas for my editing tool.

Anyway for this i opted for domtoimage and trust me i think that this is the best solution of them all.

I didn't had to face any problem of html2canvas for example:

need to be at the top of webpage so html2canvas can capture the shot completely and low dpi problem

function print()
{
    var node = document.getElementById('shirtDiv');
    var options = {
        quality: 0.95
    };

    domtoimage.toJpeg(node, options).then(function (dataUrl)
    {
        var doc = new jsPDF();
        doc.addImage(dataUrl, 'JPEG', -18, 20, 240, 134.12);
        doc.save('Test.pdf');
    });
}

Cdn for dom to image:

https://cdnjs.com/libraries/dom-to-image

Cdn for jspdf:

https://cdnjs.com/libraries/jspdf

Tags:

Javascript

Html

Canvas

Html2Canvas

Jspdf

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