draw something

        if (point1.x > -1) {
            double x0 = (point0.x > -1) ? point0.x : point1.x; //after 4 touches we should have a back anchor point, if not, use the current anchor point
            double y0 = (point0.y > -1) ? point0.y : point1.y; //after 4 touches we should have a back anchor point, if not, use the current anchor point
            double x1 = point1.x;
            double y1 = point1.y;
            double x2 = point2.x;
            double y2 = point2.y;
            double x3 = point3.x;
            double y3 = point3.y;
            // Assume we need to calculate the control
            // points between (x1,y1) and (x2,y2).
            // Then x0,y0 - the previous vertex,
            //      x3,y3 - the next one.

            double xc1 = (x0 + x1) / 2.0;
            double yc1 = (y0 + y1) / 2.0;
            double xc2 = (x1 + x2) / 2.0;
            double yc2 = (y1 + y2) / 2.0;
            double xc3 = (x2 + x3) / 2.0;
            double yc3 = (y2 + y3) / 2.0;

            double len1 = sqrt((x1-x0) * (x1-x0) + (y1-y0) * (y1-y0));
            double len2 = sqrt((x2-x1) * (x2-x1) + (y2-y1) * (y2-y1));
            double len3 = sqrt((x3-x2) * (x3-x2) + (y3-y2) * (y3-y2));

            double k1 = len1 / (len1 + len2);
            double k2 = len2 / (len2 + len3);

            double xm1 = xc1 + (xc2 - xc1) * k1;
            double ym1 = yc1 + (yc2 - yc1) * k1;

            double xm2 = xc2 + (xc3 - xc2) * k2;
            double ym2 = yc2 + (yc3 - yc2) * k2;
            double smooth_value = 0.9;
            // Resulting control points. Here smooth_value is mentioned
            // above coefficient K whose value should be in range [0...1].
            float ctrl1_x = xm1 + (xc2 - xm1) * smooth_value + x1 - xm1;
            float ctrl1_y = ym1 + (yc2 - ym1) * smooth_value + y1 - ym1;

            float ctrl2_x = xm2 + (xc2 - xm2) * smooth_value + x2 - xm2;
            float ctrl2_y = ym2 + (yc2 - ym2) * smooth_value + y2 - ym2;




            UIGraphicsBeginImageContext(drawImage.frame.size);
            //Albert Renshaw - Apps4Life
            [drawImage.image drawInRect:CGRectMake(0, 0, drawImage.frame.size.width, drawImage.frame.size.height)]; //originally self.frame.size.width, self.frame.size.height)];
            UIColor *color = [UIColor colorWithHue:.5 saturation:0.7 brightness:1.0 alpha:.5];
            CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); //kCGLineCapSquare, kCGLineCapButt, kCGLineCapRound
            CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 5.0); // for size
            //CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0.0, 1.0, 0.0, .5); //values for R, G, B, and Alpha
            CGContextSetStrokeColorWithColor(UIGraphicsGetCurrentContext(), [color CGColor]);
            CGContextBeginPath(UIGraphicsGetCurrentContext());
            //CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
            CGContextMoveToPoint(UIGraphicsGetCurrentContext(), point1.x, point1.y);
            //CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
            CGContextAddCurveToPoint(UIGraphicsGetCurrentContext(), ctrl1_x, ctrl1_y, ctrl2_x, ctrl2_y, point2.x, point2.y);
            CGContextStrokePath(UIGraphicsGetCurrentContext());
            drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();
            int offa = 100;
            int offb = 200;
            CGRect dirtyPoint1 = CGRectMake(point1.x-offa, point1.y-offa, offb, offb);
            CGRect dirtyPoint2 = CGRectMake(point2.x-offa, point2.y-offa, offb, offb);
            [self setNeedsDisplayInRect:CGRectUnion(dirtyPoint1, dirtyPoint2)];
        }