Function

CGAffineTransformRotate

Returns an affine transformation matrix constructed by rotating an existing affine transform.

Declaration

CGAffineTransform CGAffineTransformRotate(CGAffineTransform t, CGFloat angle);

Parameters

t

An existing affine transform.

angle

The angle, in radians, by which to rotate the affine transform. In iOS, a positive value specifies counterclockwise rotation and a negative value specifies clockwise rotation. In macOS, a positive value specifies clockwise rotation and a negative value specifies counterclockwise rotation.

Return Value

A new affine transformation matrix.

Discussion

You use this function to create a new affine transformation matrix by adding a rotation value to an existing affine transform. The resulting structure represents a new affine transform, which you can use (and reuse, if you want) to rotate a coordinate system.

The actual direction of rotation is dependent on the coordinate system orientation of the target platform, which is different in iOS and macOS.

See Also

Modifying Affine Transformations

CGAffineTransformTranslate

Returns an affine transformation matrix constructed by translating an existing affine transform.

CGAffineTransformScale

Returns an affine transformation matrix constructed by scaling an existing affine transform.

CGAffineTransformInvert

Returns an affine transformation matrix constructed by inverting an existing affine transform.

CGAffineTransformConcat

Returns an affine transformation matrix constructed by combining two existing affine transforms.