The algorithm uses the statistics of a cell only if there is not too much saturated pixels in it. The grey world algorithm works fine when there are a limited number of outliers. Consider a valid zone to be at least 80% of unsaturated cells in it. This value could very well be configurable, and make the algorithm more or less tolerant. While at it, implement it in a configure() call as it will not change during execution, and cache the cellsPerZone values estimated with std::round as we are using cmath. Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>