A scale of 0.5 means a magnification of two from input to output. A shift in X to be applied to the input position after the geometric transform. Shifts are always along the axes of the image. Positive values shift the image to the right. Shifts are always along the axes of the image.
Positive values shift the image upwards.
The name of a text file containing the coefficients for the geometrical transformation to be applied. These geometric transformations are always applied before the shifts, rotations and scale changes specified by other parameters. The frame in which the shifts are applied, or to put it another way, whether to apply the rotation before the shifts. See notes below for a definition of the center of rotation. Whether the reference point used in transforming the input image coordinates to the output ones is aligned on the corner or center of a pixel.