How to drag and drop an image inside a picturebox

Question

I want to be able to drag and drop an image inside a picture box, all I can find is how to drag and drop an image to a picture box but in this case I have a picture box occupying all the form height and width, the background image is a battle mat(dungeons & dragons) and what I want is to be able to move an image inside the picture box.

I have no code to display because I cannot find a way to do this.

Answer 1

Should be as simple as, saving the original image, listening for mouse events, keeping track of coordinates, and cropping on move. lacks sanity checks and fault tolerance,

private Point _origLocation;
public Bitmap _Bitmap;

private void button1_Click(object sender, EventArgs e)
{
   // create and store the original image, the one you are going to move around
   _Bitmap = new Bitmap(@"D:\Pleiades_large.jpg");
   // set it to 0,0
   SetTemp(new Point(0, 0));
}

// on mouse down capture the X/Y position so you know where to offset
private void pictureBox1_MouseDown(object sender, MouseEventArgs e) 
   => _origLocation = e.Location;

// when mouse moves do something
private void pictureBox1_MouseMove(object sender, MouseEventArgs e) 
   => SetTemp(new Point(_origLocation.X - e.Location.X, _origLocation.Y - e.Location.Y));

private void SetTemp(Point p)
{

   // if the mouse is not down, dont do anything
   if (MouseButtons != MouseButtons.Left) return;

   // Validate position, we cant move the image off the screen
   if (p.X < 0) p.X = 0;
   if (p.Y < 0) p.Y = 0;
   if (p.X > _Bitmap.Width - pictureBox1.Width) p.X = _Bitmap.Width - pictureBox1.Width;
   if (p.Y > _Bitmap.Height - pictureBox1.Height) p.X = _Bitmap.Height - pictureBox1.Height;

   // Create temp image, the size of the picture box
   var target = new Bitmap(pictureBox1.Width, pictureBox1.Height);

   using (var g = Graphics.FromImage(target))
   {
      // crop the original image to the temp image
      // thats to say, where does it need to move
      g.DrawImage(
         _Bitmap, 
         new Rectangle(0, 0, pictureBox1.Width, pictureBox1.Height), 
         new Rectangle(p.X, p.Y, pictureBox1.Width, pictureBox1.Height), 
         GraphicsUnit.Pixel);
   }

   // Dispose and assign temp image 
   pictureBox1.Image?.Dispose();
   pictureBox1.Image = target;
}