1. A method comprising: calculating an image key value, by a computing device, for image data that describes a distribution of image values of characteristics of pixels of image data; computing a tuning value by the computing device using the image key value, the tuning value configured to adjust how the image data is to be measured to compute an image compensation value; computing the image compensation value by the computing device to cause a biased statistic to approach a target value, the biased statistic placing an emphasis on one or more portions of the image data such that the biased statistic targets the image values for pixels within the one or more portions more than other portions of the image values to compute the image compensation value; and applying the image compensation value by the computing device to adjust the values of the pixels of the image data.