javaScript旋轉Base64圖片並得到新的base64數據

function rotateBase64Img(src, edg, callback) {

      var canvas = document.createElement("canvas");
      var ctx = canvas.getContext("2d");

      var imgW;//圖片寬度
      var imgH;//圖片高度
      var size;//canvas初始大小

      if (edg % 90 != 0) {
          console.error("旋轉角度必須是90的倍數!");
          throw '旋轉角度必須是90的倍數!';
      }
      (edg < 0) && (edg = (edg % 360) + 360)
      const quadrant = (edg / 90) % 4; //旋轉象限
      const cutCoor = {sx: 0, sy: 0, ex: 0, ey: 0}; //裁剪座標

      var image = new Image();
      image.crossOrigin = "anonymous"
      image.src = src;

      image.onload = function () {

          imgW = image.width;
          imgH = image.height;
          size = imgW > imgH ? imgW : imgH;

          canvas.width = size * 2;
          canvas.height = size * 2;
          switch (quadrant) {
              case 0:
                  cutCoor.sx = size;
                  cutCoor.sy = size;
                  cutCoor.ex = size + imgW;
                  cutCoor.ey = size + imgH;
                  break;
              case 1:
                  cutCoor.sx = size - imgH;
                  cutCoor.sy = size;
                  cutCoor.ex = size;
                  cutCoor.ey = size + imgW;
                  break;
              case 2:
                  cutCoor.sx = size - imgW;
                  cutCoor.sy = size - imgH;
                  cutCoor.ex = size;
                  cutCoor.ey = size;
                  break;
              case 3:
                  cutCoor.sx = size;
                  cutCoor.sy = size - imgW;
                  cutCoor.ex = size + imgH;
                  cutCoor.ey = size + imgW;
                  break;
          }


          ctx.translate(size, size);
          ctx.rotate(edg * Math.PI / 180);
          ctx.drawImage(image, 0, 0);

          var imgData = ctx.getImageData(cutCoor.sx, cutCoor.sy, cutCoor.ex, cutCoor.ey);
          if (quadrant % 2 == 0) {
              canvas.width = imgW;
              canvas.height = imgH;
          } else {
              canvas.width = imgH;
              canvas.height = imgW;
          }
          ctx.putImageData(imgData, 0, 0);
          callback(canvas.toDataURL())
      };
    }