This method does not work with black-and-white image documents (those for which ImageColorType is ICT_BlackWhite).
ImageDocument
CropImage Method of the ImageDocument Object
CropImage method of the ImageDocument Object in the ABBYY FineReader Engine API — Detects document edges and crops the image; recommended at the start of preprocessing; not applicable to black-and-white image documents.
This method finds the edges of a document on the image and then crops the image. We recommend that you call this method at the beginning of image preprocessing, before making any other modifications.