将图片的绝对路径转化成base64编码

function getBase64Image(img) {
        var canvas = document.createElement("canvas");
        canvas.width = img.width;
        canvas.height = img.height;
        var ctx = canvas.getContext("2d");
        ctx.drawImage(img, 0, 0, img.width, img.height);
        //图片的格式
        var ext = img.src.substring(img.src.lastIndexOf(".")+1).toLowerCase();
        var dataURL = canvas.toDataURL("image/"+ext);
        return dataURL;
    }
    var img = "img/bd_logo1.png";
    var image = new Image();
    image.src = img;
    image.onload = function(){
        var base64 = getBase64Image(image);
        console.log(base64);
    }