var url = "car.png"
var img = new Image();
img.src = url;
img.onload = function() {
console.log(getBase64(img,'AAAA'));
console.log(getBase64(img,'BBBB'))
}
function getBase64(img,text) {
var body = document.getElementsByTagName('body')[0];
var canvas = document.createElement("canvas");
var width = 64;
var imgWidth = 48;
var imgLeft = (width - imgWidth) / 2;
canvas.width = width;
canvas.height = width;
body.appendChild(canvas)
var cxt = canvas.getContext("2d")
cxt.drawImage(img, imgLeft, imgLeft,imgWidth,imgWidth);
cxt.font = "14px Microsoft YaHei";
cxt.textBaseline = 'top';
cxt.textAlign = 'center';
cxt.fillStyle = "#000";
cxt.fillText(text, width / 2, 0);
var dataUrl = canvas.toDataURL("image/png");
body.removeChild(canvas);
return dataUrl
}