HTML5 canvas 合成图片并保存

function draw() {
    var canvas = document.getElementById("thecanvas");
    var ctx = canvas.getContext("2d");
    var day = $('.bc_date').val();
    var myDate = new Date();
    if(day!=''){
        myDate = new Date(day);
    }

    var day = myDate.getFullYear() + "年" + (myDate.getMonth() + 1) + "月" + myDate.getDate() + "日";
    var number = "J430404-201";
    var photo = new Image();
    photo.src = "../assets/image/back.jpg";
    var name = $('.name').val();
    photo.onload = function() {
        ctx.drawImage(photo, 0, 0);
        // ctx.save();
        // ctx.rotate(-Math.PI/100);
        ctx.fillStyle = "rgba( 27, 27, 27, 0.5)";
        ctx.font = "23px simsun";
        ctx.fillText(name, 213, 213);
        ctx.fillText(day, 216, 307);
        // ctx.font = "24px simsun";
        // ctx.fillText(number,236,401);
        fit(ctx);
        saveImageInfo();

        // ctx.restore();

    };

}

function saveImageInfo() {
    var mycanvas = document.getElementById("thecanvas");
    var image = mycanvas.toDataURL("image/jpeg");
    var img = $('.image img');
    
    $(".loading").css("display", "none");
    img.attr("src", image);
    img.parent().css("display", "block");
    setTimeout(function() {
      window.location.href = image;
    }, 5000);
}
$('.commit').on('click', function() {
    draw();
});
$('.btn_close').on('click', function() {
    $(".image").css("display", "none");
});
function fit(canvas) {
    if (!browser.versions.android) {
        canvas.font = "24px simsun";
        canvas.fillText("J430404-2016", 236, 401);
    } else {
        canvas.fillText("J430404-201", 236, 401);
    }
}

demo：
结婚证生成神器