縮放UIImage size

資料來源

+ (UIImage*)imageWithImage:(UIImage*)image 
               scaledToSize:(CGSize)newSize;
{
   UIGraphicsBeginImageContext( newSize );
   [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
   UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext();

   return newImage;
}

如果要改成存JPG檔.

NSData *dataForJPEGFile = UIImageJPEGRepresentation(theImage, 0.6);

來源中還有一個依比例縮放的方式可參考.