先说下canvas绘图的基本方法,如下：
const myCanvas = document.createElement('canvas');
myCanvas.width = 400;
myCanvas.height = 400;
const ctx = myCanvas.getContext('2d');
const img = new Image();
img.src = "1.jpg";
//当图片加载完毕的时候在drawImage,否则可能图片还没有加载完毕
img.onload=()=>{
ctx.drawImage(img,100,50);
}
