1. A computer-implemented method for generating a halftone image using a spot function to binarize pixels as a function of image frequency content and pixel orientation, comprising: receiving an input image; measuring spatial activity in a local area of the input image near a given pixel; estimating a dominant orientation for pixels in the local area of the input image; selecting a pre-generated stochastic screen from a set of pre-generated stochastic screens as a function of the estimated dominant pixel orientation; determining seed points as a function of the measured spatial activity and the selected screen; evaluating a spot function at least in part as a function of a tessellation determined by seed point locations to generate an output value for each pixel; thresholding each pixel in the input image using the output value for each pixel to generate a binarized halftone image; and outputting the halftone image.