1. A method comprising: defining a tool impression in a digital image, the tool impression including a sampling region encompassing a set of pixels; iteratively modifying the sampling region within the tool impression to encompass other pixels within the tool impression, the iterative modifications to the sampling region being limited by a sampling criterion; sampling pixels in the iteratively modified sampling region to determine a first distribution of a pixel property using a processing unit; and sampling pixels in a second region within the tool impression to determine a second distribution of the pixel property using the processing unit.