1. A method of assessing image quality, comprising operating a computer processor to perform operations comprising: detecting a target object region in an input image, wherein the detecting is performed on image data derived solely from the input image without regard to image data derived from any image other than the input image and the detecting comprises determining that the target object region comprises a target object; generating an image quality feature vector representing the target object region in an image quality feature space, wherein the generating comprises generating the image quality feature vector from image data derived solely from the input image without regard to image data derived from any image other than the input image; mapping the image quality feature vector to a measure of image quality based on a classification model that correlates image quality feature vectors with respective image quality values; and outputting a quantitative assessment of quality of the input image based on the measure of image quality.