using System.Drawing.Drawing2D;
private void button3_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{ this.button3.Cursor = Cursors.Hand;
Bitmap bmpBob =(Bitmap)this.button3.Image;
GraphicsPath graphicsPath = CalculateControlGraphicsPath(bmpBob);
this.button3.Region = new Region(graphicsPath);
}
private static GraphicsPath CalculateControlGraphicsPath(Bitmap bitmap)
{

GraphicsPath graphicsPath = new GraphicsPath();

Color colorTransparent = bitmap.GetPixel(0, 0);

int colOpaquePixel = 0;

for(int row = 0; row < bitmap.Height; row ++)
{
colOpaquePixel = 0;

for(int col = 0; col < bitmap.Width; col ++)
{

if(bitmap.GetPixel(col, row) != colorTransparent)
{

colOpaquePixel = col;

int colNext = col;

for(colNext=colOpaquePixel; colNext if(bitmap.GetPixel(colNext, row) == colorTransparent)
break;

graphicsPath.AddRectangle(new Rectangle(colOpaquePixel,
row, colNext - colOpaquePixel, 1));

col = colNext;
}
}
}
return graphicsPath;
}