c#图像旋转

我需要一些帮助来解决一个真正让我头疼的问题。它是一个允许用户加载图像文件，然后将图像顺时针或逆时针旋转90度的应用程序。代码运行良好，但如果用户顺时针旋转图像，然后决定通过逆时针将其旋转回初始位置，则图像不在应有的位置。我不确定我缺少了什么，因为我对c#非常陌生。以下是我用于顺时针旋转的代码。

private int cW = 0;
private void button6_Click(object sender, RoutedEventArgs e)
{
    RotateTransform rotateTransform = new RotateTransform();
    rotateTransform.CenterX = image1.ActualWidth / 2.0;
    rotateTransform.CenterY = image1.ActualHeight / 2.0;
    cW += 90;
    rotateTransform.Angle = cW;
    TransformGroup transformGroup = new TransformGroup();
    transformGroup.Children.Add(rotateTransform);
    image1.RenderTransform = transformGroup; 
}

我已经使用if/else语句完全更改了代码。下面是我想要的结果。

RotateTransform cwRotateTransform;
private void button6_Click(object sender, RoutedEventArgs e)
{
    if (cwRotateTransform == null)
    {
        cwRotateTransform = new RotateTransform();
    }
    image1.LayoutTransform = cwRotateTransform;
    if (cwRotateTransform.Angle == 360)
        cwRotateTransform.Angle = 0;
    else cwRotateTransform.Angle += 90;
}

对于逆时针方向，只需将"90"更改为"-90"即可，否则为cwRotateTransform.Angle。

Bitmap bitmapPicturebox1;
private void Form1_Load(object sender, EventArgs e)
{
    pictureBox1.ImageLocation = @"C:'Wallpaper.jpg";
}
private void btnLeft_Click(object sender, EventArgs e)
{
    bitmapPicturebox1 = new Bitmap(pictureBox1.Image);
    bitmapPicturebox1.RotateFlip(RotateFlipType.Rotate90FlipNone);
    pictureBox1.Image = bitmapPicturebox1;
}  
private void btnRight_Click(object sender, EventArgs e)
{
    bitmapPicturebox1 = new Bitmap(pictureBox1.Image);
    bitmapPicturebox1.RotateFlip(RotateFlipType.Rotate270FlipNone);
    pictureBox1.Image = bitmapPicturebox1;
}