Merge pull request #2520 from lhnoah/master

Optimize when scale = 1

SDWebImage/SDWebImageCompat.m

@@ -57,10 +57,12 @@ inline UIImage *SDScaledImageForKey(NSString * _Nullable key, UIImage * _Nullabl
                 }
             }
             
+            if (scale != image.scale) {
                 UIImage *scaledImage = [[UIImage alloc] initWithCGImage:image.CGImage scale:scale orientation:image.imageOrientation];
                 scaledImage.sd_imageFormat = image.sd_imageFormat;
                 image = scaledImage;
             }
+        }
         return image;
     }
 #endif