JPH08279912A - Method and circuit for correcting contour - Google Patents

Abstract

PURPOSE: To prepare a required picture by generating a correction signal having amplitude set up adaptively to the amplitude of an edge signal. CONSTITUTION: An extraction circuit 10 extracts an edge signal based upon an inputted picture signal and outputs its amplitude value (k). The value (k) is suppled to a selection circuit 11 as an input address and a correction value (i) is generated from the circuit 11 while referring to an LUT and sent to a bit mask selecting circuit 12 and a comparator 13. The circuit 12 inputs the value (i) as an input address and outputs a bit mask M based upon the LUT. The comparator 13 compares the value (i) with a reference value O and outputs a high level signal when i>O or outputs a low level signal when i<O. A signal compositing circuit 14 executes OR operation between the picture signal and the bit mask M in each corresponding bit when the compared output is the high level or executes AND operation between the picture signal and the bit mask M in each corresponding bit when the compared output is the low level. Consequently required contour correction can be executed in accordance with the amplitude of the edge signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour correction method and a contour correction circuit for correcting the contour of an image signal.

[0002]

2. Description of the Related Art Conventionally, in image processing apparatuses such as printers, the contours of image signals have been corrected.

FIG. 5 is a diagram showing a configuration example of a conventional contour correction circuit, in which an image signal is input to an edge signal extraction circuit 1 and an addition circuit 3. The edge signal extraction circuit 1 extracts an edge component from the input image signal, and the edge signal extracted here is multiplied by K in the coefficient circuit 2 to be a correction signal. Then, this correction signal is added to the image signal in the addition circuit 3, whereby the contour of the image is corrected.

The contour correction circuit shown in FIG. 5 is applied to the R, G, B primary color signal systems as shown in FIG. 6A.
6B, the signal system of the luminance signal Y and the two color difference signals RY and BY are normally provided only in the luminance signal system as shown in FIG. 6B. Is.

In FIGS. 5 and 6, the image signal may be an analog signal or a digital signal. Various configurations are known as the edge signal extraction circuit 1, and any configuration may be used.

[0006]

By the way, in the conventional contour correction circuit shown in FIG. 5, the coefficient K is constant regardless of the amplitude of the edge signal. For example, if K = 2 is set,
The input / output characteristics are as shown in FIG. 7A. Further, since a portion where the edge signal level is low may include many noise components, K = 0 may be set when the absolute value of the edge signal level is equal to or lower than a predetermined level as shown in FIG. 7B. However, other than that, the value of K is constant regardless of the amplitude of the edge signal.

That is, the coefficient K of the coefficient circuit 2 is conventionally used.
The value of is constant except zero, and the input / output characteristic of the coefficient circuit 2 is linear.

However, in the conventional contour correction circuit,
Since all nonzero coefficient K values are constant, when an image signal subjected to contour correction is displayed on a monitor or when a hard copy is made by a printer, the image signal level may be small depending on the set value of K. In contrast, the contour is emphasized too much, whereas the contour is not emphasized as intended in the high level portion, or conversely, the contour is not emphasized as intended in the low image signal level portion. However, in a high level portion, the contour is emphasized more than intended, and it was very difficult to make a desired picture.

The present invention is to solve the above-mentioned problems, and by making it possible to adaptively set the level of the correction signal in accordance with the level of the edge signal, a desired contour can be created. An object of the present invention is to provide a correction method and a contour correction circuit.

[0010]

In order to achieve the above object, the contour correction method according to claim 1 multiplies an edge signal extracted based on an image signal by a coefficient to generate a correction signal, and corrects the correction signal. In a contour correction method for synthesizing a signal into an image signal, all non-zero coefficient values are not constant, but are adaptively set according to the amplitude of the edge signal.

The contour correction circuit according to a second aspect of the present invention is an edge signal extraction circuit for extracting an edge signal based on an image signal, and a correction for generating a correction signal based on the edge signal extracted by the edge signal extraction circuit. In a contour correction circuit including a signal generation circuit and a signal synthesis circuit that synthesizes a correction signal and an image signal, the correction signal generation circuit generates a correction signal having an amplitude adaptively set with respect to the amplitude of the edge signal. It is characterized by generating.

[0012]

The function of the contour correction method according to the first aspect of the present invention is as follows. This contour correction method is a contour correction method in which an edge signal extracted based on an image signal is multiplied by a coefficient to generate a correction signal, and the correction signal is combined with an original image signal. It is not constant but is adaptively set according to the amplitude of the edge signal.

Therefore, the amplitude of the correction signal, that is, the contour correction amount can be set to the optimum amplitude corresponding to the amplitude of the edge signal, so that the degree of freedom in drawing is increased, and the contour is corrected to a desired state. It is possible.

The contour correction circuit according to claim 2 is as follows. The edge signal extracted by the edge signal extraction circuit is input to the correction signal generation circuit, and the correction signal is generated. The correction signal is combined with the original image signal in a signal combining circuit to obtain an image signal whose contour is corrected.

Here, the amplitude of the correction signal generated based on the edge signal in the correction signal generation circuit has an amplitude adaptively set with respect to the amplitude of the edge signal.

Therefore, the amplitude of the correction signal can be set to the optimum amplitude corresponding to the amplitude of the edge signal, so that the degree of freedom in drawing is increased and desired contour correction can be performed.

[0017]

Embodiments will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an embodiment of a contour correction circuit according to the present invention, in which 10 is an edge signal extraction circuit, 11 is a correction value selection circuit, 12 is a bit mask selection circuit, and 13 is a comparator. , 14 are signal combining circuits.

The image signal is input to the edge signal extraction circuit 10 and the signal synthesis circuit 14. Here, it is assumed that the image signal is a digital signal and the number of bits of one pixel is N bits. Then, here, it is assumed that a bit string of pixels is input to the image signal. That is, the image signal is binary data. Of course, it is of course possible to input in the form of appropriate code data, for example, code data encoded in hexadecimal, but in such a case, as will be apparent from the later description, signal synthesis In the circuit 14, it is necessary to convert into binary data before combining with the bit mask data M.

The edge signal extraction circuit 10 extracts an edge signal based on the input image signal and outputs its amplitude value k. FIG. 2 is a diagram showing an example thereof, and when the image signal is a digitized analog signal waveform as shown in FIG. 2A, the edge signal extraction circuit 10 shows the analog signal waveform as shown in FIG. 2B. Such an edge signal is extracted and its amplitude value k is output.

Various configurations for extracting edge signals are known, and the edge signal extraction circuit 10 may have any configuration as long as it can extract those edge signals.

The amplitude value k of the edge output from the edge signal extraction circuit 10 is input to the correction value selection circuit 11. The correction value selection circuit 11 is the bit mask selection circuit 1 of the next stage.
2. The correction signal generating circuit in the contour correction circuit of the present invention is configured with the comparator 13.

First, the correction value selection circuit 11 will be described as follows. The correction value selection circuit 11 is composed of a look-up table (hereinafter referred to as LUT) that outputs the correction value i using the edge amplitude value k as an input address. FIG. 3 is a diagram showing an example of the LUT, and the correction value i is associated with the amplitude value k of the edge. That is, the correction value i is a function of the edge amplitude value k.

The correspondence between the amplitude value k and the correction value i is
It is possible to arbitrarily set the contour of the image depending on how the contour is to be corrected such that the contour is desired to be emphasized or the contour needs to be slightly corrected.

The correction value i output from the correction value selection circuit 11 is input to one input terminal of the bit mask selection circuit 13 and the comparator 13. 0 is input as a reference value to the other input terminal of the comparator 13. Then, the comparator 13 compares the correction value i with the reference value 0, outputs the first predetermined level when the correction value i is equal to or greater than the reference value 0, and the correction value i is less than the reference value 0. In some cases, the second predetermined level is output. Here, in the former case, a high level is output, and in the latter case, a low level is output.

Further, the bit mask selection circuit 12 uses the correction value i as an input address and outputs the bit mask M as an LU.
Composed of T. FIG. 4 is a diagram showing an example of the LUT, and the bit mask M is associated with the correction value i. The number of bits of each bit mask M is N bits, which is the same as the number of bits of a pixel.

In FIG. 4, the bit mask M corresponding to the positive correction value i has a predetermined lower bit of 1 and is 0 otherwise, and the bit mask M corresponds to the negative correction value i. M has a predetermined lower bit of 0, and is 1 otherwise. When the correction value i is 0, all bits are 0. Although the bit mask corresponding to the case where the correction value i is ± 1 is not shown in FIG. 4, this is when the LUT shown in FIG. 4 has the correction value selection circuit 11 having the LUT shown in FIG. This is because it shows an example of the bit mask of.

As described above, the pattern of the bit mask to be associated with each correction value i can be arbitrarily set according to what contour correction is performed.

Note that here, the LU of the correction value selection circuit 11 is
Although it is assumed that only one LUT is provided for the T and bit mask selection circuit 12, a plurality of LUTs having different characteristics are provided, and the contour correction desired by the user can be performed from the LUTs. It goes without saying that the LUT may be selected.

When the output of the comparator 13 is at a high level, the signal synthesizing circuit 14 outputs O between the image signal and the bit mask.
The R operation is performed for each corresponding bit, and when the output of the comparator 13 is at a low level, A of the image signal and the bit mask
The ND operation is performed for each corresponding bit.

For example, assuming that the edge signal value k corresponding to the pixel at the position P shown in FIG. 2A is 7 and the correction value i at this time is 3, the bit at this time is shown in FIG. As for the mask M, the bit mask selection circuit 12 outputs a bit mask in which the lower 3 bits are 1 and the others are 0. At this time, the comparator 13 outputs a high level, so that the signal synthesizing circuit 14 shown in FIG.
The logical sum of the binary data of the pixel at the position indicated by P of A and the above-mentioned bit mask is calculated, and as a result, the upper N-3 bits of the pixel are the same as the binary data of the pixel, but the lower bits. All 3 bits are 1, and the contour is emphasized by the amount that the value is increased from the input image signal.

Similarly, when the correction value i is a negative value, for example, when i = -2, the AND operation is performed in the signal synthesizing circuit 14, so that the bit shown in FIG. According to the mask, the upper N−2 bits of the binary data of the pixel are left unchanged, but the lower 2 bits are 0, and the contour of the pixel is emphasized by the reduced amount.

As described above, according to the contour correction circuit, the desired contour correction can be performed according to the amplitude of the edge signal, so that the degree of freedom of the contour correction is increased as compared with the conventional case. By doing so, desired contour correction can be performed, and desired picture making can be performed.

Further, in the conventional contour correction circuit, it is necessary to perform so-called four arithmetic operations such as multiplication and addition when performing contour correction. According to the configuration shown in FIG. Since a simple logical operation such as logical sum and logical product may be performed as 14, the contour correction can be performed with higher accuracy than before, and the circuit configuration can be simpler than before, so that the cost can be reduced. .

Although one image signal system has been described so far, this contour correction circuit can also be applied to each signal system of R, G, B primary color signals as shown in FIG. 6A. , A luminance signal Y and two color difference signals R-
For the Y and B-Y signal systems, it is also possible to apply only to the luminance signal system as shown in FIG. 6B.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications can be made. For example, it goes without saying that 0 and 1 of the bit mask shown in FIG. 4 may be reversed and the signal synthesizing circuit 14 may perform the NOR operation and the NAND operation.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a contour correction circuit according to the present invention.

FIG. 2 is a diagram for explaining input image signals and edge signals.

FIG. 3 is a diagram showing a configuration example of an LUT of the correction value selection circuit 11 of FIG.

4 is a diagram showing a configuration example of an LUT of the bit mask selection circuit 12 of FIG.

FIG. 5 is a diagram showing a configuration example of a conventional contour correction circuit.

FIG. 6 is a diagram showing an application example of a contour correction circuit.

7 is a diagram showing input / output characteristics of the coefficient circuit 2 in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Edge signal extraction circuit, 2 ... Coefficient circuit, 3 ... Addition circuit 3, 10 ... Edge signal extraction circuit, 11 ... Correction value selection circuit, 12 ... Bit mask selection circuit, 13 ... Comparator, 14
... signal synthesizing circuit, 21 ... edge signal extracting circuit, 22 ... correction signal generating circuit, 23 ... adding circuit.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] February 21, 1996

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

The correction value i output from the correction value selection circuit 11 is input to the bit mask selection circuit 12 and one input terminal of the comparator 13. 0 is input as a reference value to the other input terminal of the comparator 13. Then, the comparator 13 compares the correction value i with the reference value 0, outputs the first predetermined level when the correction value i is equal to or greater than the reference value 0, and the correction value i is less than the reference value 0. In some cases, the second predetermined level is output. Here, in the former case, a high level is output, and in the latter case, a low level is output.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

[Figure 7]

Claims (2)

[Claims] 1. In a contour correction method for generating a correction signal by multiplying an edge signal extracted based on an image signal by a coefficient and synthesizing the correction signal with the image signal, all non-zero coefficient values are not constant. A contour correction method, which is adaptively set according to the amplitude of an edge signal. 2. An edge signal extraction circuit for extracting an edge signal based on an image signal, a correction signal generation circuit for generating a correction signal based on the edge signal extracted by the edge signal extraction circuit, a correction signal and an image signal. And a signal synthesizing circuit for synthesizing the contour correcting circuit, wherein the correction signal generating circuit generates a correction signal having an amplitude adaptively set with respect to the amplitude of the edge signal. .