iOS對圖像進行尺寸壓縮

iOS Objective-C對圖像進行壓縮，最簡單的就是對圖像進行等比例縮小。代碼如下：

- (UIImage*)scaleFromImage:(UIImage*)image scaledToSize:(CGSize)newSize
{
 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<heightFactor?widthFactor:heightFactor);
      
 CGFloat scaledWidth = width * scaleFactor;
 CGFloat scaledHeight = height * scaleFactor;
 CGSize targetSize = CGSizeMake(scaledWidth,scaledHeight);
      
    UIGraphicsBeginImageContext(targetSize);
    [image drawInRect:CGRectMake(0,0,scaledWidth,scaledHeight)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}