localStorage 和 图片database64字符串转换（canvas toDataURL("image/png")）

小技巧

var src = 'public/images/sam.png';
function set(key) {
    var img = document.createElement('img');
    img.addEventListener('load', function () {
        var imgCanvas = document.createElement("canvas"),
            imgContext = imgCanvas.getContext('2d');
        imgCanvas.width = this.width;
        imgCanvas.height = this.height;
        imgContext.drawImage(this, 0, 0, this.width, this.height);
        var imgAsDataURL = imgCanvas.toDataURL("image/png");
        try {
            localStorage.setItem(key, imgAsDataURL);
        } catch (e) {
            console.log("storage failed: " + e);
        }
    }, false);
    img.src = src;//图片加载
}
function get(key) {
    var srcStr = localStorage.getItem(key);
    var imgObj = document.createElement('img');
    imgObj.src = srcStr;
    document.body.appendChild(imgObj)
}