Image deskewing mode.

Values:

IG_REC_IMG_DESKEW_AUTO	Automatic deskewing (Default).
IG_REC_IMG_DESKEW_NO	No deskewing applied.
IG_REC_IMG_DESKEW_SET	Deskew with a given angle set by the IG_REC_slope_set function.
IG_REC_IMG_DESKEW_3D	Automatic 3D deskewing applied.

Remarks:

This setting determines the deskewing mode during image preprocessing.