JPH044671A - Picture processor - Google Patents

Abstract

PURPOSE:To improve the reproducibility of a picture signal by applying filter processing suitable for the gradation gradient characteristic of the picture signal. CONSTITUTION:A picture signal inputted from a terminal T1 is sequentially inputted to one-picture-element delay elements 1a, 1b, 1c and signals ID1, ID2, ID3 are outputted from respective outputs of the elements. The signal ID2 is processed as a noted picture element in the filter processing. Both the signals ID1, ID3 are inputted to an average value arithmetic circuit 2, from which the result is outputted as an AVR signal. A divider circuit 3 receives the AVR signal and the signal ID2 and outputs the result of division as a DIV signal. A filter coefficient storage circuit 4 gives stored filter coefficients COEF1, COEF2, COEF3 to multiplier circuits 5a, 5b, 5c respectively depending on the DIV signal. The one-picture-element delay elements 1a, 1b, 1c, the multiplier circuits 5a, 5b, 5c and an adder circuit 6 form a 3-tap FIR filter, which applies filter processing to the picture signal ID and the result is outputted from a terminal T2 as a picture signal OD.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the processing of image signals read by image scanners, facsimiles, etc., and more particularly to an apparatus that performs filter processing in accordance with the gradation gradient characteristics of the image signals.

2. Description of the Related Art In general, image signal processing apparatuses perform filter processing on image signals in order to improve image reproducibility.

However, in processing the -sheet of originals, it is impossible to switch among multiple types of filter characteristics, so filter processing is performed using only one type of filter characteristic.

Therefore, it is not always possible to perform corrections that are adapted to the gradation gradient characteristics of the original, and thus image reproducibility may be poor.

Problems to be Solved by the Invention Generally, as described above, image processing apparatuses perform filter processing on image signals in order to improve image reproducibility before performing various image processing.

Filter processing corrects the frequency characteristics of the image signal, and when reading small text, etc., the frequency of the image signal increases, so it is necessary to perform filter processing with high frequency emphasis characteristics in order to improve resolution. There is.

Furthermore, when reading a document with gentle gradation changes or flat gradation, such as a photograph, it is necessary to perform filter processing with high frequency suppression characteristics in order to reproduce uniform gradation.

However, since the same filter characteristics can only be applied to the filter processing of −1 sheets of originals, there is a drawback that the image quality is inferior.

The present invention has been made in view of the above-mentioned conventional situation,
Accordingly, an object of the present invention is to provide a novel image processing apparatus that makes it possible to eliminate the above-mentioned drawbacks inherent in the conventional techniques.

Means for Solving the Problems In order to achieve the above object, an image processing apparatus according to the present invention includes an image signal storage means for storing the level of an input image signal in pixel units, and a peripheral image of the input image signal. A calculation means for calculating the average value of the signal, a division means for calculating the quotient of the average value of the peripheral image signal output from the calculation means and the input image signal, and a filter set in advance based on the division result output from the division means. The image forming apparatus includes a filter coefficient storage means for outputting coefficients, and a filter processing means for performing filter processing on the image signal output from the input image signal storage means.

Embodiment Next, a preferred embodiment of the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In FIG. 1, the image signal ID input from the terminal T1
are sequentially input to one-pixel delay elements 1a and 1bjc, and ID1. ID2 and ID3 signals are obtained.

The ID2 signal is treated as central data, that is, a pixel of interest in filter processing.

Both IDI and ID3 signals are input to the average value calculation circuit 2, and the average value is calculated in this average value calculation circuit, and the AV
It is output as an R signal.

The division circuit 3 includes the AVR signal and an ID indicating the pixel of interest.
2 signals are input, and the division result is output as a DIV signal.

The filter coefficient storage circuit 4 stores stored filter coefficients C0EFI and C0E according to the value of the DIV signal.
F2 and C0EF3 are supplied to multiplication circuits 5a, 5b, and 5c, respectively.

1-pixel delay elements 1a, lb, Ic and multiplier circuits 5a, 5b
, 5C and the adder circuit 6 constitute a 3-tap FIR filter, which performs filter processing on the image signal ID and outputs the result as the image signal OD from the terminal T2.

In this embodiment, 3 tap FI in the main scanning direction is used.
Although the R filter has been described, it is clear that a configuration combining the sub-scanning and main/sub-scanning directions is possible, and this embodiment does not limit the present invention.

Furthermore, it is clear that the interphase distance between the pixel of interest and surrounding pixels can be set separately from filter processing, and this does not limit the present invention.

As described in detail, according to the present invention, the effect of improving the reproducibility of the image signal can be obtained by performing filter processing adapted to the gradation gradient characteristic of the image signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. la, lb, 1c... 1 pixel delay element, 2... Average value calculation circuit, 3... Division circuit, 4... Filter coefficient storage circuit, 5a, 5b, 5c... Multiplication circuit, 6 ...
Adding circuit, T1. T2...terminal

Claims (2)

[Claims] (1) means for storing the level of an image signal input pixel by pixel; a calculation means for calculating an average value of image signals surrounding the input image signal; and an average of peripheral image signals output from the calculation means. a division means for calculating the quotient of a value and an input image signal; a coefficient storage means for outputting a filter coefficient preset by the division result output from the division means; and a coefficient storage means for outputting a filter coefficient set in advance from the division result output from the division means, An image processing apparatus comprising: a filter processing means for performing filter processing on an image signal. (2) The filter processing means, the input image signal level storage means, each image signal outputted from the input image signal level storage means and each corresponding filter coefficient outputted from the coefficient storage means, respectively. 2. The image processing apparatus according to claim 1, further comprising: a plurality of multipliers for multiplication; and an adder for adding signals output from the multipliers.