1. Field of the Invention
The present invention relates to a color image data processing apparatus, and more particularly, to a color image data processing apparatus comprising means for judging whether a pixel of a read image is a monochrome pixel or a color pixel other than the monochrome pixel which is provided in, for example, a digital full color copying machine. In the specification, a monochrome pixel of white, black or half-tone black having any half-tone density or gradation is referred to as a monochrome pixel hereinafter.
2. Description of the Related Art
In a conventional digital full color copying machine, a color image of an original is read every pixel by resolving the color image thereof into a red image (R), a green image (G) and a blue image (B) and converting them into respective digital image data of primary colors R, G and B, and then, the converted respective digital image data of three primary colors are subjected to color correction processes such as an under color removal process, a black adding process and a masking process or the like.
Thereafter, based on respective digital image data of cyan (C), magenta (M), yellow (Y) and black (K) which are obtained by the above-mentioned color correction processes, a cyan image, a magenta image, a yellow image and a black image are sequentially reproduced, and then, digital dot images thereof are transferred onto a sheet of copying paper, resulting in a reproduced full color image.
As one of the conventional digital full color copying machines of this type, there is known a copying machine which has a circuit for performing a color conversion process for converting a specified portion of a read color image into an image of a preferred color, for example, converting a blue image of the read color image into a red image thereof. In order to perform the above-mentioned color conversion process, there is provided a color judgement circuit for judging whether or not each pixel of the read image is a blue pixel as specified. The conventional color judgement circuit employs a table reference system using a memory which is constituted by a ROM having tables of a number equal to the kinds of specified colors, namely, four tables in the case of 4 specified colors of blue, red, yellow and black.
To address data terminals of the ROM of the color judgement circuit, there are inputted two bits selection data for selecting one of the four tables and (8.times.3) bits digital image data of three respective colors R, G and B outputted from the CCD image sensor. In this case, the ROM selects one table of the 4 tables based on the inputted selection data, and then, judges whether or not each pixel of the read color image is a pixel of the specified color based on respective inputted digital image data of three colors, thereby outputting one bit judgement result signal for indicating the judgement result.
However, since respective (8.times.3) bits digital image data for three colors R, G and B outputted from the CCD image sensor are inputted to the color judgement circuit as address data for the judgment, there is caused such problems that a memory capacity of the ROM becomes relatively large and a processing speed of the color judgement circuit is relatively low.