Color halftone image processing apparatus producing various screen angles and having an adaptive color image data conversion look-up table and a small-capacity masking memory

摘要

An image processing apparatus includes a generator for generating predetermined image data representing an image and an image reproducing device for reproducing the image. A reading device reads the image reproduced by the reproducing device and generates read data representative thereof. A converter converts the read data generated by the reading device to converted image data which is substantially equal to the predetermined image data generated by the generating device. The converting means includes a table adapted to receive the read data as address data for converting and outputting the converted image data. The converted image data may be transmitted to the reproducing device which is arranged to reproduce an image represented by either the predetermined image data or the converted image data. The image processing apparatus of the present invention may also incorporate a digitizer having a dither processing circuit for specifically processing data in accordance with a plurality of kinds of basic cells. Each cell has a number of threshold values and is of the same shape but has different arrangements of threshold values. The plurality of kinds of basic cells are alternately arranged in two perpendicular directions and are shifted relative to one another in row and column directions of the dither matrices by a and b respectively. The variables a and b represent displacements between the plural kinds of basic cells and each has a value other than zero. The dither matrix has a size NxN determined in accordance with the equation N=m(a+b) +n(a-b) where M and N are minimum values of integers and satisfy the equation M/N=(a+b)/a-b). In accordance with still a further feature of the present invention, the apparatus thereof may include an input device for inputting the image data as a plurality of bits. A first converter receives as an address the upper l bits of the image date in order to output converted image data and a second converter receives as an address the upper m bits of the image data in order to output converted data. Correcting means correct the converted image data by utilizing the converted data from the second converter and the lower n bits of the image data input by the input device.