Move cross cursor between image pixels in c# winform

Question

I have an application that will load an image into a pictureBox and will give me the value of RGB where the cross cursor is located, I can move the cursor into mutiple direction in picturebox space. Instead I want to move into image pixel space, so if I zoomed in or out I want to cursor jump from pixel to another.

any Ideas, do I need to get PixelHeight and PixelWidth of the image everytime i zoom and is Stride is how to calculate how many pixels there is?

Answer 1

Changing the Cursor.Position is simple but will interfer with actually moving the mouse.

Instead you can try this:

• Hide the real mouse cursor when you enter the picturebox
• draw a cross in the paint event while moving around
• Show the cursor again when leaving

Here is an example:

private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
    pictureBox1.Invalidate();
}

private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
    Point mouse = pictureBox1.PointToClient(Cursor.Position);
    float zoom = 1f * pictureBox1.ClientRectangle.Width / pictureBox1.Image.Width;
    int pixelWidth = (int)Math.Round(zoom);

    int x = mouse.X / pixelWidth * pixelWidth;
    int y = mouse.Y / pixelWidth * pixelWidth;

    if (pictureBox1.ClientRectangle.Contains(mouse))
    {
        e.Graphics.DrawLine(Pens.White, x, y - 4, x, y + 4);
        e.Graphics.DrawLine(Pens.White, x - 4, y, x + 4, y);
    }
}

private void pictureBox1_MouseEnter(object sender, EventArgs e)
{
    Cursor.Hide();
}

private void pictureBox1_MouseLeave(object sender, EventArgs e)
{
    Cursor.Show();
    pictureBox1.Invalidate();  // clear the last one!
}

Of course you need to calculate the pixel width only when loading or sizing the iamge. I kept it in place for clarity.