Image Processing Reference
The Perspective tool could also be called free transformation or free
distortion tool . It does offer a way of rectifying perspective distortions on an
object. However, the distortions are not interlinked (as in some tools from
other programs) and the object can be distorted from its corner points over
the two axes. The method should be good enough for images that don't have
major distortions, as is the case with this image.
Perspective correction with the Perspective tool: The dotted line depicts the original size of the layer. In the distorted trapezoidal trans-
formation frame, you can see the straightened façade of the building.