1. A method for choosing visual characteristics of a characteristic space within a region, comprising: determining a saliency based on an inverse covariance of the region and a difference between a target characteristic and a mean characteristic of the region; comparing the saliency against at least one acceptance criterion; adjusting the target characteristic and repeating the determining the saliency and comparing the saliency steps if the saliency does not satisfy the at least one acceptance criterion; and outputting the target characteristic if the saliency satisfies the at least one acceptance criterion.