Abstract: A method of producing a halftone screen having a plurality of halftone dots arrayed along a desired screen frequency. The method comprises: a) using variable size halftone dots arrayed along the screen frequency to reproduce shades of gray equal to and above a predetermined shade of gray, the predetermined shade of gray having a first halftone dot size; and b) reproducing shades of gray below the predetermined shade of gray using the first halftone dot size arrayed along the screen frequency by deleting a number of halftone dots per unit area to obtain gray shades below the predetermined shade of gray.

Abstract: A method for developing calibration curves and for calibrating a halftone imaging device to reproduce on an imaging medium gray scale values equal to input gray scale values entered in said imaging device. According to this method a calibration function representing a linear change in reproduced halftone dot size on said imaging medium as a function of input halftone dot size is developed by using the device to reproduce on an imaging medium at least two test input dot values representing two different % halftone dot sizes and determining a linear change between the input and the reproduced halftone dot sizes. The dot growth is used to predict dot changes for other % halftone dots and thus construct calibration curves which may be used to calibrate the imaging device.

Abstract: An apparatus and method of producing enhanced digital imaging for printing data, in flexographic and other types of printing environments, combines halftone screens which represent continuous "gray tone" (grey tone) levels, wherein the transition from one screen to the other is not visually detectable by an observer of the reproduction results. The digital processing method includes combining an (FM generated) dispersed dot screen with an (AM generated) cluster dot screen, with an overlay interval of both screens of acceptable resultant dot size (percent coverage), to obtain enhanced overall definition over the grey scale range of 1 to 100 percent (i.e., where 100 is equal to "255" in 8-bit environment), specifically over the more visually perceptive gray scale range of 1 to 20 (i.e., out of 0-255 value). The apparatus which implements the method algorithm is positioned intermediate a desktop publishing system and an image setter.

Abstract: A method for the nonlinear calibration of digital image data without the introduction of tonal loss is applied to image data in a computer-to-printing press system. Apparatus for implementing this method is provided. Computer processed graphics, provided from the computer in 8-bit format, are converted into 16-bit format. This 16-bit image data is then calibrated to compensate for anticipated press gain. The calibration translates the image data according to a desired nonlinear cutback (value reduction) curve of gray value reduction. Calibrated image data is then passed through 16-bit halftoning screening, the output from which is provided to the imagesetter. The implemention may include a general purpose computer with specific software resident therein, or dedicated hardware including a series of encoders and look-up table implementaion devices.

Abstract: An apparatus and method of producing enhanced digital imaging for printing data or reproduction process data (digital camera data) from the combination of dot size (amplitude) and dot density (frequency) halftone screens, whereof each halftone screen represents continuous "gray tone" (grey tone) input image levels. The method includes creating a dot frequency modulation (FM modulation--dispersed dot technique) in lighter areas which otherwise would require a dot size which is below user definable "dot size limit". This dot frequency modulation randomly deletes dots from the dot area modulation screen (AM modulation--cluster dot technique) in these lighter areas. The percentage of frequency modulation is graduated over the range of gray values which reduces objectionable visual transitions. Enhanced overall definition over the gray scale range of 0 to 100 percent (i.e., where 100 is equal to "255" in 8-bit environment), specifically over the more visually perceptive gray scale range of 0 to 20 (i.e.

Abstract: A method for generating halftone images from monochrome original images and, more particularly, to a method for reproducing a monochrome original image using at least two different colorants to create an image having a preselected hue and chroma while substantially maintaining the same lightness as in the monochrome original image.

Abstract: The principal task in graphic arts reproduction is to convert input images, such as continuous tone original images, into output images, such as half-tone images, to permit, for instance, the creation of half-tone prints on a printing press. In this process, tones (i.e., shades of gray) from the original image are typically altered or affected in two important ways. First, the printing conditions substantially affect production of an optimized half-tone representation (or match copy) of the original continuous tone image. Second, the operator often needs to modify certain tones from that in the original to bring out more or less detail to achieve a desired artistic effect. This invention allows the operator to determine and adjust for printing conditions and original tone quality in a particular system and under a particular set of operating conditions, thus greatly reducing the time-consuming experimentation that operators have previously had to endure to obtain acceptable results.