image2datauri.html

## image2datauri.html
<!DOCTYPE html>
<section>
    <input type="file" id="input" />
    <input type="number" id="maxWidth" /> &times; <input type="number" id="maxHeight" />
    <button onclick="convert()">Convert</button>
</section>
<section><pre id="output"></pre></section>
<section><img id="outputImage"></pre></section>
<script type="application/javascript">
    function convert() {
        var image = new Image;
        image.onload = function () {
            var width = image.width;
            var height = image.height;
            var maxWidth = parseInt(document.getElementById("maxWidth").value, 10) || Infinity;
            var maxHeight = parseInt(document.getElementById("maxHeight").value, 10) || Infinity;

            var scale = Math.max(1, height / maxHeight, width / maxWidth);
            width /= scale;
            height /= scale;

            var canvas = document.createElement("canvas");
            canvas.width = width;
            canvas.height = height;

            canvas.getContext("2d").drawImage(image, 0, 0, width, height);
            URL.revokeObjectURL(image.src);

            var result = canvas.toDataURL("image/png");
            document.getElementById("output").textContent = result;
            document.getElementById("outputImage").src = result;
        };
        image.onerror = alert.bind(window, "Not an image!");
        image.src = URL.createObjectURL(document.getElementById("input").files[0]);
    }
</script>