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Evaluating Affine Transforms

You can determine whether one affine transform is equal to another by calling the function CGAffineTransformEqualToTransform. This function, available in Mac OS X v10.4 and later, returns true if the two transforms passed to it are equal and false otherwise.

The function CGAffineTransformIsIdentity, available in Mac OS X v10.4 and later, is a useful function for checking whether a transform is the identity transform. The identity transform performs no translation, scaling, or rotation. Applying this transform to the input coordinates always returns the input coordinates. The Quartz constant CGAffineTransformIdentity represents the identity transform.

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