This is a little function I've built that return an image of a round corner - by selecting the border color and the fill color, the nice thing is you can use it to generate a rounded corner on the fly in your web site, it's pretty fast!

public static Bitmap RoundedCorner(ContentAlignment position ,int height, int width, Color border, Color fill)
{
    Bitmap myBmpImage = new Bitmap(1, 1);

    // Create the graphics object
    Graphics myGraphics = Graphics.FromImage(myBmpImage);
    myBmpImage = new Bitmap(myBmpImage, new Size(width, height));
    myGraphics = Graphics.FromImage(myBmpImage);

    float pX = 0;
    float pY = 0;

    if ((position == ContentAlignment.BottomLeft) || (position == ContentAlignment.BottomRight)) pY -= height;
    if ((position == ContentAlignment.BottomRight) || (position == ContentAlignment.TopRight)) pX -= width;

    // Set Background color
    myGraphics.Clear(Color.Transparent);
    myGraphics.SmoothingMode = SmoothingMode.HighQuality;
    myGraphics.TextRenderingHint = TextRenderingHint.AntiAlias;

     if (fill != null)     
        myGraphics.FillEllipse(new SolidBrush(fill), pX, pY, width * 2, height * 2);

    if (border != null)
        myGraphics.DrawEllipse(new Pen(border), pX, pY, width * 2, height * 2);

    myGraphics.Flush();
    return (myBmpImage);
}
 

Ill upload test project later on to show how it works - right now you can pretty much copy-paste it.

Cheers,

Ofir