To construct a PictureBox Control with an irregular shape that is clickable and that does not obscure other Controls "behind" it:
1. you need to have a cleaned-up bitmap (best is a 24 bit .png file with transparency) where there is a clear area around the outline of the shape.
2. you can then create a GraphicPath from this bitmap; there's an example of code showing how to do that here on CP: [^
3. using the linked to code above, you then set the Region of the PictureBox based on the graphics path, like this:
GraphicsPath g1 = CalculateControlGraphicsPath(pbLung.Image as Bitmap);
GraphicsPath g2 = CalculateControlGraphicsPath(pbClavicle.Image as Bitmap);
pbLung.Region = new Region(g1);
pbClavicle.Region = new Region(g2);
However, if you are talking about producing user-controls whose shapes follow the visible outline of an area of content in a bitmap, you are going to struggle to get quality results unless the area you want to define the shape in the bitmap has a very clear distinction between the outline and the area that surrounds it.
In most cases the visual results of creating Control/Form shapes from bitmaps are not satisfying.
Best results will occur when the shape required is defined without curves, arcs, etc.