uniapp图片转base64

网上试了几个原生方法，失败了，可以使用下面的这个方法，稳定可用

let img = new Image();
img.src = 图片地址;
img.onload = () => {
        let h = img.height; // 默认按比例压缩
	let w = img.width;
	let canvas = document.createElement('canvas');
	let ctx = canvas.getContext('2d');
	canvas.width = w;
	canvas.height = h;
	ctx.drawImage(img, 0, 0, w, h);
	let base64 = canvas.toDataURL('image/png', 1); //压缩比例
	canvas = null;
	console.log(base64)
      }

利用canvas绘制图片，然后转为base64