The term "image processing" has a broad meaning in the art. Image processing includes such operations as clarifying an input picture, recognizing a picture by abstracting characteristics thereof, and computer graphics technology, for example. Image processing also includes special effects technologies such as chroma-keying, which is an image processing method to compose two or more images according to a color in the image. For example, an announcer may stand in front of a blue screen in a studio, and a view of the outdoors is then composed with the image of the studio, within the blue background. This will make it look as though the announcer were standing outdoors. Special effects technologies also include frame composition, frame division and other special effects used in broadcasting systems. Image processing systems include digital types of image processing, analog types of image processing systems, and composite types, which are a composite of the analog and digital types. The digital type image processing system is regarded as the most important because of the high quality of processed data, reappearance, stability in information and the variety of different kinds of processing which can be performed. However, the digital type of image processing system processes an image as an aggregate of a number of pixels. This typically requires an immense number of calculation steps and therefore a long time in order to process a sufficient number of pixels with sufficient graduation, and relationship therebetween, for practical use in such areas as, for example, design use, broadcasting use, etc.
For instance, measurement of a particle-size distribution in a typical picture of 512.times.512 pixels with a graduation of 8 bits for each of the primary colors of red (R), green (G) and blue (B), has typically required about 20 minutes of calculation time for one frame, using a general purpose personal computer with a calculation processor. Even when using a supercomputer of 20 MIPs, this calculation still takes several seconds of processing time. This has prevented the prior art image processor from being used in real-time.
In order to solve such a problem of a long calculation period, special-purpose integrated circuits (ICs) have been proposed. For instance, a cathode ray tube controller (CRTC) has been proposed for affine transformation or for displaying of a picture, and a specialized integrated circuit for image analyzing of a predetermined number of pixels has been proposed. Unfortunately, these special purpose ICs are only applicable to narrow and specialized types of image processing. A system including such special purpose ICs therefore has a low cost-performance because of its narrowly restricted application. Since such ICs are designed without considering the cooperation with other ICs, particularly ICs made by other companies, it has been substantially impossible to construct a multi-purpose image processing system by using a plurality of such ICs.
Some special-purpose hardware systems have been designed for special manufacturing lines. Such systems are, however, usually useful for only one purpose and restricted in their operating conditions. When the particular condition is not that which was intended, a frequent measurement error may occur, or measurement may become impossible. Newly improved image processing algorithms cannot be introduced into such systems due to their lack of flexibility.
For improving the process speed of image processing hardware or IC, a pipe-line architecture is usually applied.
However, a processing speed of a portion in the hardware is sometimes not enough for achieving the highest pipe-line process speed during a critical process condition.