Rotates the user coordinate system in a context.
SDKs
- iOS 2.0+
- macOS 10.0+
- Mac Catalyst 13.0+
- tvOS 9.0+
- watchOS 2.0+
Framework
- Core Graphics
Declaration
void CGContextRotateCTM(CGContextParameters
cA graphics context.
angleThe angle, in radians, by which to rotate the coordinate space of the specified context. Positive values rotate counterclockwise and negative values rotate clockwise.)
Discussion
The direction that the context is rotated may appear to be altered by the state of the current transformation matrix prior to executing this function. For example, on iOS, a UIView applies a transformation to the graphics context that inverts the Y-axis (by multiplying it by -1). Rotating the user coordinate system on coordinate system that was previously flipped results in a rotation in the opposite direction (that is, positive values appear to rotate the coordinate system in the clockwise direction).