Specify an apsulute number of pixels or an percentage by passing a value between 1 and 0.
Specify a value for this argument to cause the deskewed image to be auto-cropped. The argument is the pixel width of the image background (e.g. 40). A width of 0 disables auto cropping.
Straightens an image. A threshold of 40% works for most images.
Skew is an artifact that occurs in scanned images because of the camera being misaligned, imperfections in the scanning or surface, or simply because the paper was not placed completely flat when scanned.