CGContextClip

CGContextClip is a function in the Core Graphics framework of Apple's operating systems, including macOS and iOS. It is used to modify the current clipping region of a graphics context. The clipping region defines the area within which subsequent drawing operations will be visible. Anything drawn outside this region will be discarded.

When CGContextClip is called, it effectively replaces the current clipping region with the path that has been defined and set as the current path for the graphics context. This means that any subsequent drawing commands, such as drawing lines, filling shapes, or drawing images, will only be rendered within the boundaries of this new path.

To use CGContextClip, you first need to define a path. This can be done using various Core Graphics path functions, such as CGPathCreateMutable, CGPathMoveToPoint, CGPathAddLineToPoint, CGPathAddRect, or CGPathAddEllipseInRect. Once the path is constructed, it is set as the current path of the graphics context using CGContextAddPath. Following this, CGContextClip is called to make this path the new clipping region.

The primary purpose of clipping is to restrict drawing to specific areas, which can be useful for various graphical effects, such as creating masks, drawing within defined shapes, or preventing drawing outside a designated boundary. It is an essential tool for controlling the rendering output in Core Graphics.