RenderingContext如何实现canvasContext.drawImage的功能？
const ctx = canvas.getContext('2d');
let img = canvas.createImage();
img.src = imgUrl;
img.onload = (e) => {
ctx.drawImage(img, 0, 0, 60, 60);
wx.canvasGetImageData({
canvasId: canvasId,
x: 0,
y: 0,
width: 60,
height: 60,
fail(e){
// 输出canvas内容是 empty， 要如何获取imageData
}
})
};
