js 怎麼改變URL圖片的大小並生成新的URL

我想做的是要將原始圖片縮小，並且生成新的地址

var canvas1 = document.createElement("canvas");
      document.body.appendChild(canvas1);
      var context = canvas1.getContext("2d");
      var img = new Image();
      img.setAttribute("crossOrigin", "anonymous");//不加這個會連接會是空白的
      img.src = url;
      img.onload = oEvent => {
        console.log(img.width, "img.width");
        console.log(img.height, "img.height");
        canvas1.width = img.width;
        canvas1.height = img.height;
        canvas1.fillStyle = "#FF000000";
        img.height = img.height * percentage;
        img.width = img.width * percentage;
        img.crossOrigin = "anonymous";//不加這個會連接會是空白的
        canvas1.setAttribute("width", img.width + "px");
        canvas1.setAttribute("height", img.height + "px");
        console.log(img, canvas1.toDataURL());
        context.drawImage(img, 0, 0, img.width, img.height);
        let a = canvas1.toDataURL();
        url = canvas1.toDataURL();
        );
      };