What is the difference between CGContextAddLineToPoint and addLineToPoint function in UIBezierPath?

Question

I have rendered some basic shapes using quartz-2d. I came across two methods to draw a line. First is to get a context using UIGraphicsGetCurrentContext() and then draw the line using CGContextAddLineToPoint.

And other way is to define a UIBezierPath object and draw using its function addLineToPoint

[bezierPath addLineToPoint:CGPointMake(10, 10)];

And then I have to add bezierPath to the context using CGContextAddPath.

So I wanted to know the difference between these two approaches as both are used to draw only a line. Is there a performance issue between these two? Also which method is better under what circumstances.

Answer 1

The UIBezierPath is an object from the UIKit, and allow you to use a set of function mixing particular curve with control point but also with a normal line.

Being an object from the UIKit you are not able to use CGContextAddLineToPoint, but anyway at the end you need to add the path in the context with CGContextAddPath.

With CGContexAddLineToPoint instead you draw directly on the context.

So my suggest is to use this last way if you have not particular reasons (like amazing curve with different control point). Otherwise, use UIBezierPath.

Answer 2

The CGContextAdd.. functions are lower-level C Quartz2D API that bridge between CGContext and CGPathRef instances. You use a CGContext when you want to draw something, while CGPathRef is the structure that manages geometric shapes.

On the other hand, UIBezierPath is an Objective-C UIKit class that wraps around CGPath, and provides also some bridge to CGContext functions, for example with setFill, setStroke, fill or stroke methods.

Is totally safe to mix the two approaches, but it's sure that CGContext gives you more tools. Performance and memory are better with direct CGContext calls, but performance difference are absolutely negligible in 99% of the cases.