Improve background trim from ink card scans

[gfiumara]

A call for contributions is open for improved algorithms that better deal with segmented ink scans, which may contain a black border and whose paper region may be a pixel intensity of ~220-240. The algorithm must be optimized enough to not (or only marginally) increase computation time. There’s much in the academic literature about this problem. NFIQ 1 employed its own heuristic to remove ink scan background noise.

The improved algorithm would replace copyRemovingNearWhiteFrame() and would be contributed to ISO/IEC 29794-4 in a future revision.

Source: Comment US-020 from ISO/IEC JTC 1/SC 37/WG 3 N 1416 (Clause 5.1.4.2)