Reveal portions of an image behind another image

问题

I have a PictureBox where I display an image (Let's call it Image1). There's a second image (Image2) which needs to be revealed as the user hovers the Image1 with the mouse. I only need to reveal part of Image2 (a 10X10 pixel size box), not the whole image as the mouse moves.

Both images are BMP.

How can I accomplish this task? I would think using overlays?

I display the Image1 in the picturebox and then I load the Image2 in memory, now I just need to display the portions of the Image2 over Image1 as the mouse moves.

Thank you,

回答1:

Here is an example:

public Form1()
{
    InitializeComponent();
    pictureBox1.Image = Bitmap.FromFile(your1stImage);
    bmp = (Bitmap)Bitmap.FromFile(your2ndImage);
    pb2.Parent = pictureBox1;
    pb2.Size = new Size(10,10);
    /* this is for fun only: It restricts the overlay to a circle: 
    GraphicsPath gp = new GraphicsPath();
    gp.AddEllipse(pb2.ClientRectangle);
    pb2.Region = new Region(gp);
    */

}

Bitmap bmp;
PictureBox pb2 = new PictureBox();

private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
{
    Rectangle rDest= pb2.ClientRectangle;
    Point tLocation =   new Point(e.Location.X - rDest.Width - 5, 
                                  e.Location.Y - rDest.Height - 5);
    Rectangle rSrc= new Rectangle(tLocation, pb2.ClientSize);

    using (Graphics G = pb2.CreateGraphics() )
    {
        G.DrawImage(bmp, rDest, rSrc, GraphicsUnit.Pixel);
    }
    pb2.Location = tLocation;
}

It uses offsets the overly to the top left of the Cursor adding a little for smooth movement..

来源：https://stackoverflow.com/questions/28501353/reveal-portions-of-an-image-behind-another-image