Patent US 5,457,541

An improved method and apparatus for calibrating halftone output images is provided which calibrates subsequent halftone input images with varying imagesetter outputs such as image resolutions, exposure intensities and screen frequencies. Calibration is programmably achieved by programmably selecting a specific calibration set for each corresponding uncalibrated halftone input image. The selected calibration set and mapping transfer function automatically compensates or adjusts the uncalibrated input image for any value of resolution, intensity and screen frequency to produce a calibrated halftone output image in either positive or negative sense output and usable on either paper or film photographic medium. Once the calibrated halftone output is programmably produced, it can then be photoprocessed according to conventional chemical processing means. The present invention represents a substantial improvement in precision and speed by which halftone output images are calibrated in the typeset industry.