JPH0451773A - Picture processing unit - Google Patents

Abstract

PURPOSE:To obtain a picture processing unit implementing pseudo halftone processing without production of unique texture even between picture elements with a small density change by rearranging data for each line so as to select the direction of the processing. CONSTITUTION:A picture signal inputted from an input terminal 9 is stored in an input picture line memory 10. An odd number line and even number line detection section 12 detects a noted line to be an odd number or an even number and outputs the result. An input picture line memory address counter 11 counts up an odd number line in the forward direction based on an output of the odd number line and even number line detection section 12 and counts down an even number line in the reverse direction to read the input picture signal of the input line memory in the forward or reverse direction according to the result of count. A read picture is subjected to error spread processing by an error spread processing section 23, stored in an output picture line memory 20, the result is read as the output picture signal in the forward direction and outputted from an output terminal 22.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to image processing devices, particularly facsimiles, copying machines, D
The present invention relates to a device that is used in a TP device, a workstation, etc. and performs pseudo halftone processing.

2. Description of the Related Art Conventionally, this type of image processing apparatus is known as, for example, Japanese Patent Laid-Open No. 64
There are the ones shown in Japanese Patent No. 18368 and the one shown in FIG.

The image processing device shown in FIG. 5 includes an input terminal 1 for inputting an image signal, an adder 2 for performing addition processing on a plurality of data, a darkness value generation section 3, and a comparator for comparing the darkness value and the input signal. 4, a subtracter 5 that takes the difference between the input signal and the output signal of the comparator 4, an error memory 6 that stores the error obtained by the subtracter 5, and a weighting device for a plurality of input signals. has a weighted adder 7 for performing addition and an output terminal 8.

Then, an adder 2 adds a weighted cumulative error signal, which is the output of an adder 7, to the image signal inputted from the input terminal 1, and outputs it as a corrected image signal. Comparator 4
Then, the corrected image signal outputted from the adder 2 and the threshold value from the dark value generation section 3 are respectively input, binarized, and output as a binarized signal from the output terminal 8. The subtracter 5 uses the corrected image signal output from the adder 2 and the comparator 4.
A binarized signal, which is the output of the pixel, is input, the voltage is reduced, and the result is output as a binarization error in the pixel of interest.

The error memory 6 stores the error that is the output of the subtracter 5. The adder 7 already assigns 2 weights to the pixel of interest.
Weights are assigned to the errors of a plurality of peripheral pixels that have been converted into values, and this value is input, the weights are added, and the adder 2 adds the weights to the input image signal in processing the pixels of the next line. As a result, pseudo halftone processing called error diffusion processing is performed.

Problems to be Solved by the Invention However, in such a conventional image processing device, during the error diffusion processing operation, the scanning direction in both the main scanning direction and the sub-scanning direction is as shown in FIG. Since the direction is constant from left to right and from top to bottom, the direction of error propagation is also fixed diagonally from the top left to the bottom right. Therefore, in areas where the concentration change is small, the diagonal angle of 45 degrees or 1
There is a problem in that a unique texture in which black pixels or white pixels are continuous in a 35-degree direction is generated, which deteriorates the smoothness of the image quality.

The present invention has been made in view of the above problems, and an object thereof is to provide an image processing device that can perform pseudo halftone processing without generating a unique texture even between pixels with small density changes. .

Means for Solving the Problems In order to achieve the above object, the present invention detects whether a line of interest is an odd line or an even line as a means for inputting or outputting an image signal to a means for error diffusion processing. input image line memory means for storing input image signals, rearranging the image signals line by line in forward and reverse directions according to the detection results of the odd-numbered and even-numbered line detection means, and outputting them to the error diffusion processing means; , and output image line memory means for inputting the output of the error diffusion processing means and outputting the images rearranged in the forward and reverse directions in the forward direction.

Effect With the above configuration, in the image processing apparatus of the present invention, input image signals are arranged line by line in order or in reverse order and the data arrangement type is arranged by the input image line memory before being input to the error diffusion processing means. be done. After pseudo-halftone processing is performed by the error diffusion processing means, the data is rearranged by the output image line memory in the order in which it was first input and output. As a result, the direction of error propagation changes from lower left to lower right for each line, which reduces the correlation between the appearance of dots and the previous line, making it possible to suppress the occurrence of unique textures. .

Embodiment FIGS. 1 and 2 are diagrams showing a first embodiment of an image processing apparatus according to the present invention.

In FIG. 1, reference numeral 9 denotes an input terminal for inputting an image signal;
10 is an input image line memory that stores the image signal input from the input terminal 9; 11 is an address counter for the input line memory; 12 is an odd line/even line detection unit that detects odd lines and even lines; 13 is a plurality of 14 is an adder that performs addition processing on data; 14 is a weighted adder that performs weighted addition on a plurality of input signals; 15;
16 is a comparator that compares the threshold value with the input signal; 17 is a subtracter that takes the difference between the input signal and the output signal of comparator 1G; and 18 is a storage for the error determined by the subtracter 5. Error memory 19 is an address counter for the error memo January 8, 20 is an output image line memory that stores output images, rearranges the images in the forward direction, and outputs them; 21 is an output image line memory 20. Address counter 22 is an output terminal to which an image signal subjected to error diffusion processing is output. Then, an adder 13, a weighting adder 14, a threshold generation section 15, a comparator 16,
The subtracter 17 and the error memory address counter 19 constitute an error diffusion processing section 23, as in the conventional example. The input image line memory 10 stores input image signals, and outputs the image signals arranged line by line in forward and reverse directions according to the detection results of the odd-numbered and even-numbered line detection means.

The operation of the image processing apparatus having such a configuration will be described below.

The image signal input from the input terminal 9 is stored in the input image line memory 10. Odd line/even line detection unit 12
Now, detect whether the line of interest is odd or even, and output the result. The input image line memory address counter 11 counts up in the forward direction (from 0 to Max) if the line is an odd number based on the output of the odd line/even line detection section 12, and counts down in the reverse direction if the line is an even number. (from Max to 0). The input image signal stored in the input image line memory is read out in the forward or reverse direction according to the count of the input image line memory address counter 11. The image read from the 0 input image line memory i month O is subjected to error diffusion processing. Error diffusion processing is performed in section 23. The error memory address counter 19 also performs up-counting or down-counting according to the output of the odd line/even line detection section 12, and the error diffusion processing section 23
Give the read and write addresses for the error memo January 8th.

The image signal binarized by the error diffusion processing section 23 is stored in the output image line memory 20. The output image line memory address counter 21 also performs up-counting or down-counting according to the output of the odd line/even line detection section 12, and provides a write address to the output image line memory 20.

The output image signal stored in the output image line memory 20 is read out in the forward direction and output from the output terminal 22. The direction of the processing of reading from the input image line memory 10, writing to the output image line memory 20, and reading and writing to the error memory 18, which are executed under the control of the odd line/even line detection section 12, is determined. Shown in Figure 2.

Inside the error diffusion processing section 23, in the adder 13,
The weighting that has already been calculated for the image signal is added to the adder 1.
The cumulative error image output from 4 is added.

The corrected image signal, which is the output of the adder 13, is sent to the comparator 16.
The image is binarized using the darkness value output from the threshold value generating section 15. The binarized image signal is output as the output of the error diffusion processing section 23. In the SiX device 17, the comparator 16
The binarized symbol, which is the output of the adder 13, and the corrected image signal, which is the output of the adder 13, are input, subtracted, and output as a binarized error signal.

In addition, in the embodiment described above, the error diffusion processing section 23
In order to add a dither pattern to the input image signal internally, multiple types of weight coefficient sets for the adder may be prepared and these sets may be randomly switched. In order to prevent blurring caused by error propagation at edges that change from an area to a white area (or vice versa), the output section forces the output when the input multilevel image signal is greater than a predetermined high-level threshold. The output may be set to 1, but the output may be forcibly replaced with 0 when the output is smaller than a predetermined low level threshold.

FIG. 4 is a diagram showing a second embodiment of the image processing apparatus according to the present invention.

In this embodiment, a random number generator 24 is used instead of the odd line/even line detector 12 in the first embodiment.
It is characterized by having the following. The other configurations are the same as the first embodiment.

In the image processing apparatus having such a configuration, the random number generation section 24 generates 110 random numbers for each line. The input line address counter 11 inputs the random number output from the random number generator 24, and based on the random number, counts up in the forward direction (from 0 to Max) or counts down in the reverse direction (from Mar to O). The input image signal stored in the image line memory 10 is read out in the forward or reverse direction according to the count of the input image line memory address counter 11. Further, the output image line memory address counter 21 and the error memory 18 address counter 19 also input the random number output from the random number generator 24, and based on the random numbers, count up in the forward direction (from 0 to Max) or in the reverse direction. Count down to (M
ax to 0). Therefore, the image signal stored in the output image line memory 20 is read out in the forward direction and output from the output terminal 22. This allows the input image line memory 1 to be executed under the control of the random number generator 24.
The processing directions for reading from 0, writing to the output image line memory 20, and reading and writing to the error memo January 8 are as follows:
Unlike the first embodiment shown in FIG. 2, the forward and reverse directions are completely random.

Note that in this second embodiment as well, a dither pattern may be added to the input image signal within the error diffusion processing section 23, as in the first embodiment. Alternatively, as shown in FIG. 3, the weighting may be performed by preparing a plurality of weight count sets for the adder and switching these sets at random. moreover,! 4.
In order to prevent blurring caused by error propagation at edge portions that change from a region to a white region (or vice versa), the output section outputs a signal when the input multilevel image signal is larger than a predetermined high-level darkness value. While the output is forced to 1, the output may be forced to 0 when the output is smaller than a predetermined low level darkness value.

As described in detail, according to the present invention, when performing pseudo halftone processing on an image signal, the data is rearranged for each line to switch the direction of processing, thereby reducing errors from the previous line. The correlation between the appearance of the dots is reduced, the dots are dispersed, and the generation of unique textures is prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of an image processing apparatus according to the present invention, FIG. 2 is a schematic diagram showing the direction of processing for each line in the embodiment, and FIG. 3 is a diagram showing the first embodiment. FIG. 4 is a block diagram showing a second embodiment of the image processing device according to the present invention, FIG. 5 is a block diagram showing an example of a conventional image processing device, FIG. 6 is a schematic diagram showing the direction of conventional error diffusion processing operation. 9... Input terminal, 10... Input image line memory,
11.19.21...Address counter, 12...
Odd line/even line detection unit, 20... Output image line memory, 22... Name of output terminal agent Patent attorney Shigetaka Awano 1 person (figure)

Claims (2)

[Claims] (1) Image signal input means for inputting an image signal, odd line/even line detection means for detecting whether the line of interest is an odd line or an even line, and storing the image signal input from the image signal input means, An input image line memory means for rearranging and outputting image signals line by line in the forward and reverse directions according to the detection results of the line/even line detection means, and an error in the image signal output from the input image line memory means. It consists of an error diffusion processing means for performing a diffusion process, and an output image line memory means for inputting the output of the error diffusion processing means and outputting the images rearranged in the forward and reverse directions in the forward direction. Image processing device. (2) A random number generating means is provided in place of the odd line/even line detecting means, and the output of the random number generating means rearranges the image signals line by line in the forward and reverse directions and stores them in the input image line memory means. 2. The image processing apparatus according to claim 1, wherein the image processing apparatus outputs a digital image signal.