private void toolStripRotateClockwise_Click(object sender, EventArgs e)
 {
     Image i = pictureBox1.Image;
     i.RotateFlip(RotateFlipType.Rotate90FlipNone);
     pictureBox1.Image = i;
 }

 private void toolStripRotateCounterClockwise_Click(object sender, EventArgs e)
 {
            Image i = pictureBox1.Image;
            i.RotateFlip(RotateFlipType.Rotate270FlipNone);
            pictureBox1.Image = i;
 }

 private void toolStripButtonPreviousImage_Click(object sender, EventArgs e)
 {
     if (counter > 0)
     {
        counter -= 1;
     }
     else
     {
        counter = fileNames.Length - 1;
     }
     pictureBox1.Load(fileNames[counter]); // Exception: ImageLocation must be set.
 }

  private void toolStripButtonNextImage_Click(object sender, EventArgs e)
  {
      string directoryPath = Path.GetDirectoryName(openFileDialog1.FileName);
      DirectoryInfo di = new DirectoryInfo(directoryPath);
      FileInfo[] fi = di.GetFiles();
      fileNames = new string[fi.Length];
      int j = 0;
      foreach (FileInfo fi2 in fi)
      {
          if (fi2.Extension == ".jpg" || fi2.Extension == ".jpeg" || fi2.Extension == ".gif" || fi2.Extension ==

".bmp" || fi2.Extension == ".png")
          {
              fileNames[j] = fi2.FullName;
              j++;
          }
      }
      if (counter < fileNames.Length - 1)
      {
          counter += 1;
      }
      else
      {
          counter = 0;
      }
          pictureBox1.Load(fileNames[counter]); // Exception: ImageLocation must be set.
}