draw a sawtooth view

SawtoothView.m

- (void)drawRect:(CGRect)rect
{
    const CGFloat frequency = 25.0f;
    const CGFloat amplitude = 5.0f;
    const CGFloat baseLineHeight = 50.0f; // if base line height equal to amplitude, the sawtooth is on the edge of the view
    // Drawing code
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSaveGState(context);
    CGContextSetLineWidth(context, 2.0f); // set line width
    CGContextSetStrokeColorWithColor(context, [UIColor purpleColor].CGColor); // set stroke color
    CGContextSetFillColorWithColor(context, [UIColor purpleColor].CGColor); // set fill color
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathMoveToPoint(path, NULL, 0, 0);
    for (float x = 0; x < self.frame.size.width; ++x) {
        float y = sinf(frequency * x / 180*M_PI) * amplitude + baseLineHeight;
        CGPathAddLineToPoint(path, NULL, x, y);
    }
    CGPathAddLineToPoint(path, NULL, rect.size.width, 0);
    CGPathAddLineToPoint(path, NULL, 0, 0);
    CGPathCloseSubpath(path); // close path
    
    CGContextAddPath(context, path);
    CGContextDrawPath(context, kCGPathFillStroke);
    CGPathRelease(path);
    CGContextRestoreGState(context);
}