js实现二维码在线解码的方法_二维码解码

$(function () {
    document.getElementById("uploadBtnd").onchange = function (e) {
        var canvas = $('#decode-canvas')[0],
           ctx = canvas.getContext('2d'),
          file = e.target.files[0],
          reader = new FileReader();
        reader.onload = (function (e) {
            var img = new Image();
            img.onload = function () {
                canvas.width = img.width;
                canvas.height = img.height;
                ctx.drawImage(img, 0, 0);
            };
            img.src = e.target.result;
        });
        file && reader.readAsDataURL(file);
    };
});
function renderLogo(canvas, url) {
    var img = new Image(),
          ctx = canvas.getContext('2d'),
          canvasSize = 200;
    if (!url) {
        ctx.fillStyle = 'rgb(255, 255, 255)';
        ctx.fillRect(0, 0, canvasSize, canvasSize);
        return;
    }
    img.onload = function () {
        var imgSize, zoom,
            imgW = img.width, imgH = img.height;
        canvas.width = canvasSize;
        canvas.height = canvasSize;
        ctx.fillStyle = 'rgb(255, 255, 255)';
        ctx.fillRect(0, 0, canvasSize, canvasSize);
        imgSize = Math.max(imgW, imgH);
        if (imgSize > canvasSize) {
            zoom = canvasSize / imgSize;
            imgW = imgW * zoom;
            imgH = imgH * zoom;
        }
        ctx.drawImage(img, (canvasSize - imgW) / 2, (canvasSize - imgH) / 2, imgW, imgH);
    };
    img.src = url;
}
$('#decode-btn').on('click', function () {
    result = $('#decode-canvas').QRDecode(function (e) {
        $("#decoderes").val(e.message);
        throw e;
    });
    if (result) {
        $("#decoderes").val(result);
    }
});
function empty() {
    $("#decoderes").val("");
    $("#uploadBtnd").val("");
}