adjustable canvas dimensions determined by chosen images

I would like to create a canvas image based on the selected image

<canvas id="canvas" ></canvas>
<input type="file" id="file-input">

Using JavaScript:

$(function() {
    $('#file-input').change(function(e) {
        var file = e.target.files[0],
            imageType = /image.*/;

        if (!file.type.match(imageType))
            return;

        var reader = new FileReader();
        reader.onload = fileOnload;
        reader.readAsDataURL(file);

    });

    function fileOnload(e) {
        var $img = $('<img>', { src: e.target.result });
        var canvas = $('#canvas')[0];
        var context = canvas.getContext('2d');

        $img.load(function() {
            context.drawImage(this, 0, 0);
        });
    }
});

Although the file is successfully written to the canvas, the issue I am encountering is that it only displays within the dimensions of the canvas.

Is there a way to automatically adjust the canvas size to match that of the selected image?

Here is a JSFIDDLE DEMO

Furthermore, the drawn image appears much larger compared to the original image size.

Answer №1

Unfortunately, I am unable to comment on the previous answer due to a lack of points.

Consider updating the dimensions of the canvas DOM element by adjusting the height and width.

var canvas = document.getElementsByTagName('canvas')[0];
$img.load(function() {
        canvas.width  = this.width;
        canvas.height = this.height;
        context.drawImage(this, 0, 0);
});

Check out the Working Demo: jsfiddle

Answer №2

$(document).ready(function() {
$('#file-input').on('change', function(e) {
    var file = e.target.files[0],
        imageType = /image.*/;

    if (!file.type.match(imageType))
        return;

    var reader = new FileReader();
    reader.onload = handleFileLoad;
    reader.readAsDataURL(file);

});

function handleFileLoad(e) {
    var $image = $('<img>', { src: e.target.result });
    var canvas = $('#canvas')[0];
    var context = canvas.getContext('2d');

    $image.on('load', function() {
        canvas.width  = this.width;
        canvas.height = this.height;
        context.drawImage(this, 0, 0);
    });
}
});

Answer №3

After the image has loaded, it is essential to retrieve the dimensions (specifically the width and height) of the image and then adjust the canvas dimensions accordingly:

    $img.onload = function() {
        canvas.width = this.width;
        canvas.height = this.height;
        context.drawImage(this, 0, 0);
    };

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