void HatchTrellis(CGContext context)
{
var hatchWidth = getHatchWidth (hatchStyle);
var hatchHeight = getHatchHeight (hatchStyle);
var lineWidth = getLineWidth (hatchStyle);
initializeContext(context, hatchHeight, false);
/* draw background */
drawBackground (context, foreColor, hatchWidth, hatchHeight);
context.SetFillColor(backColor.ToCGColor());
CGRect rect = new CGRect (0,0,2,1);
setPixels(context, rect);
rect.X = hatchWidth / 2.0f;
rect.Y = hatchHeight / 2.0f;
setPixels(context, rect);
}