1. A method comprising: capturing, by a camera of a mobile computing device, an image; determining whether the image includes a representation of at least a portion of a face; and when the image includes the representation of at least the portion of the face: computing a difference between a tonal distribution of the image and a tonal distribution of each previously classified image from a group of previously classified images, wherein the tonal distribution is associated with a darkness-based mapping of a plurality of pixels of the image, wherein at least one previously classified image from the group of previously classified images is classified as a good quality image, and wherein at least one previously classified image from the group of previously classified images is classified as a poor quality image; determining a smallest computed difference between the tonal distribution of the image and the tonal distribution of a previously classified image from the group of previously classified images based at least in part on the computed differences; and classifying, by the mobile computing device, a quality of the image by at least classifying the image as being of a same quality as the previously classified image associated with the smallest computed difference.