CGAffineTransform

An affine transformation matrix for use in drawing 2D graphics.

Overview

A transformation specifies how points in one coordinate system map to points in another coordinate system. An affine transformation is a special type of mapping that preserves parallel lines in a path but does not necessarily preserve lengths or angles. Scaling, rotation, and translation are the most commonly used manipulations supported by affine transforms, but skewing is also possible.

For more information on how to create, concatenate, and apply affine transformations, see Quartz 2D Programming Guide.

You typically do not need to create an affine transform directly—CGContext describes functions that modify the current affine transform. If you don’t plan to reuse an affine transform, you may want to use CGContextScaleCTM, CGContextRotateCTM, CGContextTranslateCTM, or CGContextConcatCTM.

Topics

Creating an Affine Transformation Matrix

CGAffineTransformMake

Returns an affine transformation matrix constructed from values you provide.

CGAffineTransformMakeRotation

Returns an affine transformation matrix constructed from a rotation value you provide.

CGAffineTransformMakeScale

Returns an affine transformation matrix constructed from scaling values you provide.

CGAffineTransformMakeTranslation

Returns an affine transformation matrix constructed from translation values you provide.

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.

CGAffineTransformRotate

Returns an affine transformation matrix constructed by rotating 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.

Applying Affine Transformations

CGPointApplyAffineTransform

Returns the point resulting from an affine transformation of an existing point.

CGSizeApplyAffineTransform

Returns the height and width resulting from a transformation of an existing height and width.

CGRectApplyAffineTransform

Applies an affine transform to a rectangle.

Evaluating Affine Transforms

CGAffineTransformIsIdentity

Checks whether an affine transform is the identity transform.

CGAffineTransformEqualToTransform

Checks whether two affine transforms are equal.

Data Types

CGAffineTransform

An affine transformation matrix for use in drawing 2D graphics.

Constants

CGAffineTransformIdentity

The identity transform.