Draw part of a circle

Question

For an iPhone application I want to draw a circle, that is only for an x percentage filled.

Something like this:

Answer 1

Try this:

CGContextMoveToPoint(the center point)
CGContextAddLineToPoint(the starting point of the fill path on the circumference)
CGContextAddArcToPoint(the ending point of the fill path on the circumference)
CGContextAddLineToPoint(the center point)
CGContextFillPath

Answer 2

Below is a full method I am using that does this with Core Graphics, adapting and expanding on mharper's comment above.

This code is for OSX Cocoa, but could easily be changed to iOS, by modifying how you get the context.

- (void)drawPieShapedCircleWithRadius:(CGFloat)radius
                      strokeColor:(CGColorRef)strokeColor
                        fillColor:(CGColorRef)fillColor
                        lineWidth:(CGFloat)lineWidth
                   currentDegrees:(float)currentDegrees
                     startDegrees:(float)startDegrees {
    // get the context
    CGContextRef context = [[NSGraphicsContext currentContext] graphicsPort];

    // Set the color of the circle stroke and fill
    CGContextSetStrokeColorWithColor(context, strokeColor);
    CGContextSetFillColorWithColor(context, fillColor);

    // Set the line width of the circle
    CGContextSetLineWidth(context, 1);

    // Calculate the middle of the circle
    CGPoint circleCenter = CGPointMake(self.frame.size.width / 2, self.frame.size.height / 2);

    // Move the bezier to the center of the circle
    CGContextMoveToPoint(context, circleCenter.x, circleCenter.y);  // move to the center point

    // Draw the arc from the start point (hardcoded as the bottom of the circle) to the center
    CGContextAddLineToPoint(context, circleCenter.x, circleCenter.y + radius);

    // Draw the arc around the circle from the start degrees point to the current degrees point
    CGContextAddArc(context, circleCenter.x , circleCenter.y, radius, [self radians:startDegrees], [self radians:startDegrees + currentDegrees], 0);

    // Draw the line back into the center of the circle
    CGContextAddLineToPoint(context, circleCenter.x, circleCenter.y);

    // Fill the circle
    CGContextFillPath(context);

    // Draw the line around the circle
    CGContextStrokePath(context);
}