public static void Rotate90(string fileName)
{
Image Pic;
string FileNameTemp;
System.Drawing.Imaging.Encoder Enc = System.Drawing.Imaging.Encoder.Transformation;
EncoderParameters EncParms = new EncoderParameters(1);
EncoderParameter EncParm;
ImageCodecInfo CodecInfo = GetEncoderInfo("image/jpeg");
// load the image to change
Pic = Image.FromFile(fileName);
Image Pic2 = (Image)Pic.Clone();
// we cannot store in the same image, so use a temporary image instead
FileNameTemp = fileName + ".temp";
// for rewriting without recompression we must rotate the image 90 degrees
EncParm = new EncoderParameter(Enc, (long)EncoderValue.TransformRotate90);
EncParms.Param[0] = EncParm;
// now write the rotated image with new description
Pic.Save(FileNameTemp, CodecInfo, EncParms);
Pic.Dispose();
Pic = null;
// delete the original file, will be replaced later
//System.IO.File.Delete(fileName);
//System.IO.File.Move(FileNameTemp, fileName);
}