1. A system for automatically determining emotional content of a digital image using a dimensional space model with valence and arousal coordinates, comprising: a programmed computer having memory and an input for receiving the digital image from the memory of a device used to capture or store the digital image, wherein the computer is programmed to perform the following functions automatically: (a) extract visual information from the digital image; (b) extract shape features in the image to compute computational constructs of visual properties including roundness and angularity and compute the computational constructs; and (c) compute information relating to the emotional content of the digital image using a dimensional space model of emotions with valence and arousal coordinates based upon the extracted shape features, the extracted visual information, or computed computational constructs of visual properties; and an output device in communication with the programmed computer enabling a user to receive the computed information relating to the emotional content of the image, wherein the extracted visual information includes color or texture of the digital image; wherein the extracted shape features comprise one or more of line segments, continuous lines, angles, or curves; wherein the roundness in the image is automatically computed by fitting the shape features extracted from the image to a circle characterized by how closely the extracted shape features of the image approaches that of a circle, and wherein the angularity in the image is automatically computed by: a) fitting the shape features extracted from the image to ellipses and measuring an elongatedness of the fitted ellipses, and characterized by maximum elongatedness of the fitted ellipses, or b) a statistical measure of a distribution of angles computed between extracted intersecting line segments, the statistical measure being one of the minimum value, the maximum value, a percentile, the difference between percentiles, the difference between the maximum and minimum values, the total number of angles, the median angle, the mean angle, or a standard deviation of angles.