Foreground ink in the rank-label strip of a left-edge square

Foreground ink in the rank-label strip of a left-edge square

Usage

label_ink(mat, row)

Arguments

mat

A grayscale board matrix from to_gray_matrix().

row

The 0-indexed board row whose left-edge label strip to measure.

Value

The fraction of strip pixels that differ strongly from the local background (higher means more ink, i.e. a wider digit such as 8).