How do I rotate a picture in WinForms

Here's a method you can use to rotate an image in C#:

/// <summary>
/// method to rotate an image either clockwise or counter-clockwise
/// </summary>
/// <param name="img">the image to be rotated</param>
/// <param name="rotationAngle">the angle (in degrees).
/// NOTE: 
/// Positive values will rotate clockwise
/// negative values will rotate counter-clockwise
/// </param>
/// <returns></returns>
public static Image RotateImage(Image img, float rotationAngle)
{
    //create an empty Bitmap image
    Bitmap bmp = new Bitmap(img.Width, img.Height);

    //turn the Bitmap into a Graphics object
    Graphics gfx = Graphics.FromImage(bmp);

    //now we set the rotation point to the center of our image
    gfx.TranslateTransform((float)bmp.Width / 2, (float)bmp.Height / 2);

    //now rotate the image
    gfx.RotateTransform(rotationAngle);

    gfx.TranslateTransform(-(float)bmp.Width / 2, -(float)bmp.Height / 2);

    //set the InterpolationMode to HighQualityBicubic so to ensure a high
    //quality image once it is transformed to the specified size
    gfx.InterpolationMode = InterpolationMode.HighQualityBicubic;

    //now draw our new image onto the graphics object
    gfx.DrawImage(img, new Point(0, 0));

    //dispose of our Graphics object
    gfx.Dispose();

    //return the image
    return bmp;
}

This will work as long as the image you want to rotate is already in your Properties resources folder.

In Partial Class:

Bitmap bmp2;

OnLoad:

 bmp2 = new Bitmap(Tycoon.Properties.Resources.save2);
            pictureBox6.SizeMode = PictureBoxSizeMode.StretchImage;
            pictureBox6.Image = bmp2;

Button or Onclick

private void pictureBox6_Click(object sender, EventArgs e)
        {
            if (bmp2 != null)
            {
                bmp2.RotateFlip(RotateFlipType.Rotate90FlipNone);
                pictureBox6.Image = bmp2;
            }
        }

I have modified the function of Mr.net_prog which gets only the picture box and rotate the image in it.

    public static void RotateImage(PictureBox picBox)
    {

        Image img = picBox.Image;
        var bmp = new Bitmap(img);

        using (Graphics gfx = Graphics.FromImage(bmp))
        {
            gfx.Clear(Color.White);
            gfx.DrawImage(img, 0, 0, img.Width, img.Height);
        }

        bmp.RotateFlip(RotateFlipType.Rotate270FlipNone);
        picBox.Image = bmp;
    }

This solution assumes that you want to draw the image in a picture box and that the image orientation will follow the mouse movements over this picture box. No image is assigned to the picture box. Instead I'm getting the image from a project resource.

private float _angle;

public Form1()
{
    InitializeComponent();
}

private void PictureBox_MouseMove(object sender, MouseEventArgs e)
{
    (float centerX, float centerY) = GetCenter(pictureBox1.ClientRectangle);
    _angle = (float)(Math.Atan2(e.Y - centerY, e.X - centerX) * 180.0 / Math.PI);
    pictureBox1.Invalidate(); // Triggers redrawing
}

private void PictureBox_Paint(object sender, PaintEventArgs e)
{
    Bitmap image = Properties.Resources.ExampleImage;
    float scale = (float)pictureBox1.Width / image.Width;

    (float centerX, float centerY) = GetCenter(e.ClipRectangle);

    e.Graphics.TranslateTransform(centerX, centerY);
    e.Graphics.RotateTransform(_angle);
    e.Graphics.TranslateTransform(-centerX, -centerY);
    e.Graphics.ScaleTransform(scale, scale);
    e.Graphics.DrawImage(image, 0, 0);
}

// Uses C# 7.0 value tuples / .NET Framework 4.7.
// For previous versions, return a PointF instead.
private static (float, float) GetCenter(Rectangle rect)
{
    float centerX = (rect.Left + rect.Right) * 0.5f;
    float centerY = (rect.Top + rect.Bottom) * 0.5f;
    return (centerX, centerY);
}

Make sure to to select the mouse event handlers PictureBox_MouseMove and PictureBox_Paint in properties window of the picture box for these events, after you copy/pasted this code into the form.

Note: You could also use a simple Panel or any other control, like a label; however, the PictureBox has the advantage to use double buffering by default, which eliminates flickering.