The Book of GIMP

16.1 Global Transformations

Global transformations are transformations that act on an entire image or layer, rather than on an object or region, and act by rearranging pixels, rather than by calculating new values. Perhaps counterintuitively, global transformations require relatively little computing power because they change the position of pixels but don’t create empty spaces within the image or require interpolation. (To interpolate pixels is to compute new pixels by using the values of neighboring pixels.) For example, when using the Rotate tool to rotate an image, all the pixels in the image layer must be interpolated. Rotation is not a global transformation. The Flip tool, which does perform a global transformation, simply changes the position ...