Drawing a moving sine wave anti-aliased

Question

I want to draw a moving sine wave with variable frequency and variable amplitude in a crisp and anti-aliased way. How is this possible?

Answer 1

Made a more complete, and swift version of GeneratorOfOne's version. This one also fills the bottom of the wave with a chosen color:

class WaveView: UIView {

    private var maskPath: UIBezierPath!
    @IBInspectable var fillColor: UIColor = UIColor.blueColor()
    @IBInspectable var cycles: CGFloat = 7

    override func drawRect(rect: CGRect) {

        var w: CGFloat = 0              // Starting position
        let width = rect.width
        let y: CGFloat = rect.height
        let yc: CGFloat = rect.height / 2
        let x = width/cycles

        let context = UIGraphicsGetCurrentContext();
        CGContextSetFillColorWithColor(context, UIColor.greenColor().CGColor);
        let path = CGPathCreateMutable();

        CGPathMoveToPoint(path, nil, 0, 0)

        while (w<=rect.width) {
            CGPathMoveToPoint(path, nil, w,y/2);
            CGPathAddQuadCurveToPoint(path, nil, w+x/4, -yc, (w+x/2), y/2);
            CGPathMoveToPoint(path, nil, w+x/2,y/2);
            CGPathAddQuadCurveToPoint(path, nil, w+3*x/4, y+yc, w+x, y/2);
            w+=x;
        }

        CGPathAddLineToPoint(path, nil, rect.width, rect.height)
        CGPathAddLineToPoint(path, nil, 0, rect.height)
        CGPathAddLineToPoint(path, nil, 0, y/2);
        CGPathCloseSubpath(path)

        maskPath = UIBezierPath(CGPath: path)
        maskPath.lineCapStyle = CGLineCap.Square
        maskPath.lineJoinStyle = CGLineJoin.Miter

        CGContextAddPath(context, path);
        CGContextSetFillColorWithColor(context, fillColor.CGColor)
        CGContextFillPath(context)
    }

}