The patterns can be used to reduce one or more undesirable effects such as moire or colour shift in coloured halftone images. Colour screens in the images are based on a combination of non-orthogonal mesh structures with parcels of printing dots which have common shape and size. Preferably the dots grow in mid tones by extending first towards their second, third or fourth nearest neighbours.

A method for producing a half-tone image faithfully representing a continuous-tne original includes a step of forming in the image a pattern of substantially continuous, substantially parallel lines at a frequency of between about 100 and 400 lines per inch, such that the width of the lines at a given point in the image varies in relation to the optical density of at least one color component at a corresponding point in the continuous-tone original. The method may be used for color separations w...

A method for generating a screened reproduction of an image includes the steps of providing a representation of an original, defining a desired screen dot arrangement for the image, and writing screen dots in a line by line fashion. The representation of an original has input density values representing the grey levels of various locations of the original for a given color separation. Each screen dot is made up of a plurality of line segments whose length and location determines the dot configur...

A computer program and method for generating from a 1-bit image data file a multiple-bit image data file, which, when displayed on a computer display screen, resembles an image that would appear on an output medium as a result of an output device printing the 1-bit file, the program being operable to carry out, and the method comprising, the steps of: receiving a 1-bit image data file and first and second values that characterize actual regions of the output medium that would be marked by the ou...

Method of optimizing a reproduction of a picture copy includes scanning a picture copy optoelectrically for generating scanning signals, in accordance with the scanning signals, electronically screening the picture copy and inscribing a recording medium so that one of a plurality of screen fields on the recording medium corresponds to one or more scanning signals of the picture copy, forming each of the screen fields, respectively, of a plurality of elementary cells, and determining relative loc...

A host computer converts an entered gray scale image into a raster image expressing multiple tonal ranges, using an intermediate spot pattern determined in advance. Here, the intermediate spot pattern is a spot pattern composed of pixels which can take only binary value densities with information indicating tonal ranges embedded in the manner of arrangement of the pixels in the spot pattern. Therefore, this raster image logically expresses a large number of tonal ranges which cannot be actually ...

In a moire fringes eliminating apparatus, a moire fringe eliminating unit comprises a halftone dot feature extracting unit, a re-calculation unit, a re-calculation deciding unit, and a halftone dot shape changing unit. The halftone dot feature extracting unit extracts features of the halftone dots. The re-calculation unit obtains a re-calculation deciding value which represents a ratio between a total number of the halftone dots in a neighboring area and the number of the halftone dots having a ...

A gradation-corrected image data is generated by converting an input gradation image data depending on conditions of an output machine and thereafter scanning a recording medium in the output machine with a light beam based on the gradation-corrected image data. Specifically, an amount-of-exposure distribution is calculated based on a shape of recording dots corresponding to input gradations and specification details of the light beam step. Then, a density distribution of an image on the recordi...

A digital halftoning technique for controlling a spot function is disclosed. A method for generating a spot for use in halftoning according to the present invention includes defining a spot function that combines two functions selected to provide a predetermined spot shape for use in a halftone cell and scaling the spot function using a scaling function that varies according to a value of a first and second spot function ordinate. Asymmetric modulation of spot functions is used to control the to...

A combined dot density and size modulation system uses dispersed dot halftoning in conjunction with dot size modulation to produce a halftone image in which both the density and size of the dots are modulated to control overall gray level. The dot density and size modulation system offers advantages over pure dot density modulation systems or pure dot size modulation systems because it allows an extra degree of flexibility which can be used to increase the visual quality of the halftoned pattern...