Quartz 2D 画贝塞尔曲线

- (void)drawRect:(CGRect)rect {
    
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    // Drawing with a white stroke color
    CGContextSetRGBStrokeColor(context, 1.0, 1.0, 1.0, 1.0);
    // Draw them with a 2.0 stroke width so they are a bit more visible.
    CGContextSetLineWidth(context, 2.0);
    
    // Draw a bezier curve with end points s,e and control points cp1,cp2
    CGPoint s = CGPointMake(30.0, 120.0);
    CGPoint e = CGPointMake(300.0, 120.0);
    CGPoint cp1 = CGPointMake(120.0, 30.0);
    CGPoint cp2 = CGPointMake(210.0, 210.0);
    CGContextMoveToPoint(context, s.x, s.y);
    CGContextAddCurveToPoint(context, cp1.x, cp1.y, cp2.x, cp2.y, e.x, e.y);
    CGContextStrokePath(context);
    
    // Show the control points.
    CGContextSetRGBStrokeColor(context, 1.0, 0.0, 0.0, 1.0);
    CGContextMoveToPoint(context, s.x, s.y);
    CGContextAddLineToPoint(context, cp1.x, cp1.y);
    CGContextMoveToPoint(context, e.x, e.y);
    CGContextAddLineToPoint(context, cp2.x, cp2.y);
    CGContextStrokePath(context);
    
    // Draw a quad curve with end points s,e and control point cp1
    CGContextSetRGBStrokeColor(context, 1.0, 1.0, 1.0, 1.0);
    s = CGPointMake(30.0, 300.0);
    e = CGPointMake(270.0, 300.0);
    cp1 = CGPointMake(150.0, 180.0);
    CGContextMoveToPoint(context, s.x, s.y);
    CGContextAddQuadCurveToPoint(context, cp1.x, cp1.y, e.x, e.y);
    CGContextStrokePath(context);
    
    // Show the control point.
    CGContextSetRGBStrokeColor(context, 1.0, 0.0, 0.0, 1.0);
    CGContextMoveToPoint(context, s.x, s.y);
    CGContextAddLineToPoint(context, cp1.x, cp1.y);
    CGContextStrokePath(context);
}