如何使用CoreGraphics绘制半圆

Question

I am trying to draw a semicircle using Core Graphics and Filling it with some color.I want to replace color with image by using CALayer. Can any one help how to do this Thanks!

Code goes here.

CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 2);
CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);
CGContextMoveToPoint(context, 0, 500);
CGContextAddArc(context, 60, 500, 50, 90, 180, 0);
CGContextStrokePath(context);

Answer 1

You need to specify the angles in radians , not degrees. 180 degrees = π radians. So in your example:

CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 2);
CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);
CGContextMoveToPoint(context, 10, 500);
CGContextAddArc(context, 60, 500, 50, M_PI / 2, M_PI, 0);
CGContextStrokePath(context);

Note that I also moved the starting point (…MoveToPoint) 10 pixels to the right, because that's where the arc begins.

Answer 2

The given answers are not working on iOS 7 for me!
I created a little category to create a circle with the angle of a percentage. Maybe you wanna check it out.
You can still adopt the methode if you only want to create a semicircle.
Here is the: GitHub Link
And that is what its look like:

Answer 3

CGPoint circleCenter = CGPointMake(self.bounds.size.width / 2, self.bounds.size.height / 2);

CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 2);
CGContextMoveToPoint(context, circleCenter.x, circleCenter.y);


CGContextAddArc(context, circleCenter.x, circleCenter.y, 50, 90, 180, 0);
CGContextAddLineToPoint(context, circleCenter.x, circleCenter.y);
CGContextSetFillColorWithColor(context, [UIColor colorWithPatternImage:[UIImage imageNamed:@"add-icon.png"]].CGColor);
CGContextFillPath(context);

CGContextAddArc(context, circleCenter.x, circleCenter.y, 50, 180, 90, 0);
CGContextAddLineToPoint(context, circleCenter.x, circleCenter.y);
CGContextSetFillColorWithColor(context, [UIColor colorWithPatternImage:[UIImage imageNamed:@"appIcon_58.png"]].CGColor);
CGContextFillPath(context);

Answer 4

What you need, which I found the other day, is a great tool that lets you visualise Core Graphics code - after drawing it in a graphics program.

Its called Paint Code.

PaintCode