JPH09200530A - Image processing device - Google Patents

Abstract

(57) Abstract: An image processing device capable of smooth edge enhancement processing is obtained. A Laplacian filter Rap. F emphasizes and detects the edge signal of the input image signal ORG. The edge component of the emphasized edge signal is smoothed by the smoothing circuit. The output signal of this smoothing circuit and the input image signal O
RG is added by the adder circuit to form the output signal OUT1. Since the smoothed edge signal is added to the input signal ORG, it is possible to perform smooth edge enhancement processing of the input image signal ORG.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus that performs edge enhancement processing on an image.

[0002]

2. Description of the Related Art Conventionally, image processing apparatuses generally carry out edge enhancement processing for sharpening an image. For example, there is JP-A 64-2474, "Image Processing System". In this conventional example, a printer output with good gradation reproducibility and image quality can be obtained not only for a manuscript in which halftone pictures are printed by characters or printing, but also for a manuscript whose brightness or color changes gently such as a photograph of a landscape or a person. It is said that it will provide an image processing system that can do this.

An example of a conventional signal processing procedure will be specifically described. FIG. 11 is a block diagram showing a circuit configuration example of a conventional arithmetic circuit. The arithmetic circuit shown in FIG. 11 has the Laplacian filter Rap. F and
It is composed of a ½ arithmetic unit that halves the gain of a signal and an adder that adds two input signals into one signal. Symbol ORG is an original signal input to this circuit, and OUT is an output signal.

In the arithmetic circuit constructed as above,
The input original signal (ORG) is Rap. One of the signals processed by F and the 1/2 operation unit and the other unprocessed ORG signal are input to the adder and added.

The ORG signal is, for example, the signal shown in FIG. 13, and this ORG signal is the Rap. The edge portion is subjected to waveform processing at F, and becomes a signal having a waveform of FIG. This signal Edg has a gain of ½ in the ½ arithmetic unit, is added to the signal ORG in the adder, and the signal OUT is output. The arithmetic expression of the above procedure is the following expression (1). Also,
The form of the waveform of the OUT signal is shown in FIG.

OUT = ORG + {Edg × (1/2)} (1)

[0007]

However, in the edge detection by the Laplacian filter or the like in the conventional image processing apparatus, only one line portion of the edge is emphasized, as can be seen from FIG. As a result, there is a problem that a gradual and smooth edge enhancement effect cannot be obtained.

It is an object of the present invention to provide an image processing device which enables smooth edge enhancement processing.

[0009]

In order to achieve the above object, an image processing apparatus of the present invention includes a Laplacian filter for enhancing and detecting an edge signal of an input image signal, and a smoothing edge component of the enhanced edge signal. The smoothing circuit for converting the input image signal into the smoothing circuit and the adding circuit for adding the output signal of the smoothing circuit to the input image signal are provided to enable smooth edge enhancement processing of the input image signal.

Further, the processing of enhancing the edge signal of the input image signal by the Laplacian filter and the smoothing circuit may be applied only to the positive edge component of the input image signal.

Further, the image processing apparatus has a table which is a signal converted according to the amount and / or the polarity of the edge signal which has been emphasized, and based on the output signal converted by this table, the emphasis signal is enhanced. It is good to perform processing.

At least two Laplacian filters are used.
It is preferable that the filter is composed of different types of filters, and the magnitude of the absolute value of the output signal of each of the at least two types of filters is determined, and the output of the edge amount is switched according to the determination result to perform emphasis.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of an image processing apparatus according to the present invention will be described in detail with reference to the accompanying drawings. FIG.
~ Referring to Fig. 10, there is shown one embodiment of the image processing apparatus of the present invention. Of these figures, FIGS. 1 to 4 show circuit configuration examples of four types of arithmetic circuits, FIGS. 5 to 7 show filter configuration examples, and FIGS. 8 to 10 show processed waveforms. Hereinafter, in order to make the description easy to understand, the process of signal processing will be described as one-dimensional.

<First Arithmetic Circuit> FIG. 1 is a block diagram showing a circuit configuration example of the first arithmetic circuit of the present embodiment.
The first arithmetic circuit shown in FIG. 1 is the filter Rap. F and this Rap. It is composed of a smoothing circuit that smoothes the output signal of F and an adder that adds two input signals into one signal. Symbol O
RG is the original signal input to this circuit, and OU
T1 is an output signal.

In the first arithmetic circuit configured as described above, the input original signal (ORG) is Ra
p. One signal processed by F and the smoothing circuit,
The unprocessed other ORG signal is input to the adder and added.

The ORG signal is the signal shown in FIG. This ORG signal is the Rap. At F, the edge portion is subjected to waveform processing and becomes the signal Edg having the waveform of FIG. The smoothing circuit is composed of, for example, the filter shown in FIG. The edge portion of the signal Edg is smoothed by this filter to become Edg1 as shown in FIG. The smoothed signal E shown in FIG.
The dg1 and the input signal ORG shown in FIG. 13 are added by the adder to form the output signal OUT1 shown in FIG. FIG.
The output signal OUT1 of FIG.
It can be seen that the edge enhancement is smoother than the output signal OUT shown in FIG. The procedure of signal processing by the circuit of FIG. 1 can be expressed by the following equation (2). OUT1 = ORG + Edg1 (2)

<Second Operation Circuit> FIG. 2 is a block diagram showing an example of the circuit configuration of the second operation circuit of this embodiment.
The second arithmetic circuit shown in FIG. 2 is the filter Rap. F and a positive area determination circuit that determines a positive area based on the signal obtained by this filter,
An attenuator circuit that reduces the gain to ½ and a smoother circuit that smoothes the signal, and selects either the output signal of the attenuator circuit or the output signal of the smoother circuit based on the determination signal of the above positive region determination circuit. And a selector that adds the input signal ORG and the output signal of the selector into a single signal. The output signal of the adder is the output signal OUT2 of the present arithmetic circuit.

FIG. 10 is a result corresponding to the input signal ORG processed by the second arithmetic circuit shown in FIG. It can be seen that in this result, the rising edge is sharper than in the first result of FIG. 9, and the smoothness of the edge enhancement of the image portion is maintained.

<Third Arithmetic Circuit> FIG. 3 is a block diagram showing a circuit configuration example of the third arithmetic circuit of the present embodiment.
The third arithmetic circuit shown in FIG. 3 is the filter Rap. F and this Rap. A smoothing circuit for smoothing the output signal of F, a table for converting the edge amount of the output signal of the smoothing circuit based on a predetermined coefficient, and 2
And an adder that adds two input signals into one signal. The signal added by the adder is the output signal OU
It becomes T3. In the circuit configuration in FIG. 3, the smoothing circuit and the end of the table do not affect the output result.

<Fourth Arithmetic Circuit> FIG. 4 is a block diagram showing a circuit configuration example of the fourth arithmetic circuit according to the present embodiment.
The fourth arithmetic circuit shown in FIG. 4 has a fill Rap1 composed of FIG. 6 and a fill Rap2 composed of FIG.
And a selector that selects an output signal of Rap1 or Rap2 based on an absolute value magnitude comparison circuit that compares the magnitudes of the absolute values of these output signals, a smoothing circuit that smoothes, and an edge amount of the output signal of the smoothing circuit. Is configured based on a predetermined coefficient, and an adder that adds two input signals into one signal. The signal added by the adder becomes the output signal OUT4.

The Laplacian filters shown in FIGS. 6 and 7 have different output data depending on the edge direction. Since the edge amount obtained by these Laplacian filters differs depending on the edge direction, it becomes easy to suppress the occurrence of unevenness in the edge enhancement.

[0022]

As is apparent from the above description, the image processing apparatus of the present invention enhances and detects the edge signal of the input image signal, smoothes the edge component of the enhanced edge signal, and smooths it. The output signal and the input image signal are added. Therefore, it is possible to obtain an input image signal that has undergone smooth edge enhancement processing.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a first arithmetic circuit that is an embodiment of an image processing apparatus of the present invention.

FIG. 2 is a block diagram showing a configuration example of a second arithmetic circuit.

FIG. 3 is a block diagram showing a configuration example of a third arithmetic circuit.

FIG. 4 is a block diagram showing a configuration example of a fourth arithmetic circuit.

FIG. 5 is a diagram showing a configuration example of a smoothing circuit.

FIG. 6 is a diagram showing a configuration example of a Laplacian filter Rap1.

FIG. 7 is a diagram showing a configuration example of a Laplacian filter Rap2.

8 is a diagram showing a waveform example of an output signal Edg1 of the smoothing circuit of FIG.

FIG. 9 is a diagram showing an example of a waveform of an output signal OUT1 of the first arithmetic circuit.

FIG. 10 is a diagram showing a waveform example of an output signal OUT2 of the second arithmetic circuit.

FIG. 11 is a block diagram showing a configuration example of an arithmetic circuit of a conventional image processing apparatus.

FIG. 12 is a conventionally used Laplacian filter R.
ap. It is a figure which shows the structural example of F.

FIG. 13 is a diagram showing an example of the form of an input image signal ORG.

14 is a diagram showing an example of the form of an edge signal Edg processed by the Laplacian filter of FIG.

15 is a diagram showing the output signal OUT of FIG. 11. FIG.

[Explanation of symbols]

ORG input image signal OUT1, OUT2, OUT3 output image signal after edge processing

Claims (4)

[Claims] 1. A Laplacian filter for enhancing and detecting an edge signal of an input image signal, a smoothing circuit for smoothing an edge component of the enhanced edge signal, an output signal of the smoothing circuit and the input image. An image processing apparatus comprising: an adder circuit for adding a signal and a signal, which enables smooth edge enhancement processing of an input image signal. 2. The process of enhancing the edge signal of the input image signal by the Laplacian filter and the smoothing circuit is applied only to a positive edge component of the input image signal. Image processing device. 3. The image processing apparatus further comprises a table which is a signal converted according to the amount and / or the polarity of the edge signal that has been emphasized, and based on the output signal converted by the table, The image processing apparatus according to claim 1, wherein the enhancement processing is performed. 4. The Laplacian filter is composed of at least two types of filters, the magnitude of the absolute value of the output signal of each of the at least two types of filters is determined, and the output of the edge amount is switched according to the determination result. The image processing apparatus according to claim 1, wherein the enhancement is performed.