ios对图像进行压缩源码

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{
 CGSize imageSize = image.size;
 CGFloat width = imageSize.width;
 CGFloat height = imageSize.height;

 if (width <= newSize.width && height <= newSize.height){
  return image;
 }

 if (width == 0 || height == 0){
  return image;
 }

 CGFloat widthFactor = newSize.width / width;
 CGFloat heightFactor = newSize.height / height;
 CGFloat scaleFactor = (widthFactor