WO2014091720A1

WO2014091720A1 - Contour correction device and image processing device

Info

Publication number: WO2014091720A1
Application number: PCT/JP2013/007126
Authority: WO
Inventors: 板倉　章太郎
Original assignee: パナソニック株式会社
Priority date: 2012-12-10
Filing date: 2013-12-04
Publication date: 2014-06-19
Also published as: JPWO2014091720A1

Abstract

The present invention enables contour correction to be suitably executed even when an image contains an oblique line. A first correction unit (11) calculates a first correction amount for correcting contours in horizontal and vertical direct ions, and a second correction unit (12) calculates a second correction amount for correcting a contour in a direction orthogonal to an oblique line at a prescribed angle. A degree-of-obliqueness detection unit (13) detects a degree of obliqueness representing the extent to which the image approxima tes the oblique line at the prescribed angle. A signal correction unit (20) adjusts the first correction amount and the second correction amount according to the degree of obliqueness, and corrects a luminance signal by using the adjust ed correction amounts.

Description

Outline correction apparatus and image processing apparatus

The present disclosure relates to image processing, and particularly relates to contour correction processing for correcting the contour of an image.

Conventionally, a technique for highlighting the contour of an image has been used in order to make the edges in the image visually clearer. In Japanese Patent Laid-Open No. 2004-228561, contour correction with a visually low sense of incongruity is realized by switching the gain of the contour signal in a non-linear manner according to a change in luminance signal. Further, as in Patent Document 2, by adding a horizontal contour correction signal and a vertical contour correction signal to the video signal, it is possible to enhance the contour of the image two-dimensionally and improve the sharpness. Become.

JP-A-3-36884 JP-A-61-125287

However, in the conventional method, contour correction is performed in the horizontal direction and the vertical direction. Therefore, when there is a diagonal line in the image, the contour correction is performed in both the horizontal direction and the vertical direction with respect to the diagonal line. It will take. As a result, the contour correction for the oblique line is overcorrected, and jaggies and shoots are excessively emphasized. As a result, there is a problem that the quality of the image quality is deteriorated.

This disclosure is intended to appropriately perform contour correction even when there is a diagonal line in an image.

In one aspect of the present disclosure, a contour correction device that corrects a contour of an image represented by a luminance signal calculates a first correction amount for performing contour correction in a horizontal direction and a vertical direction from the luminance signal. A second correction unit that calculates a second correction amount for performing contour correction in a direction orthogonal to the diagonal line at a predetermined angle from the luminance signal, and an image from the luminance signal to the diagonal line at the predetermined angle. An inclination degree detecting unit that detects an inclination degree that represents the degree of approximation, the first correction amount and the second correction amount are adjusted according to the inclination degree, and the luminance signal is used using the adjusted correction amount. And a signal correction unit for correcting.

According to this aspect, the oblique degree detecting unit detects the oblique degree representing the degree to which the image approximates the oblique line of the predetermined angle. Then, in the signal correction unit, a first correction amount for performing contour correction in the horizontal direction and the vertical direction and a second correction amount for performing contour correction in a direction orthogonal to the oblique line of a predetermined angle are detected. Adjustment is made according to the degree of inclination, and the luminance signal is corrected using the corrected amount after adjustment. As a result, it is possible to apply the contour correction in the oblique direction while avoiding the overcorrection applied to the oblique line while applying the contour correction in the horizontal direction and the vertical direction to the vertical line and the horizontal line in the image. . Therefore, even when there is a diagonal line in the image, the contour correction can be appropriately executed.

According to the present disclosure, it is possible to appropriately perform contour correction even when there is a diagonal line in the image.

It is a block diagram which shows the structural example of the outline correction apparatus which concerns on embodiment. 1 is a specific configuration example of a contour correction apparatus according to an embodiment. (A), (b) is a figure for demonstrating the inclination degree detection. (A), (b) is a figure for demonstrating the inclination degree detection. It is a figure for demonstrating diagonal outline correction | amendment. It is an example of the blend method of the horizontal / vertical outline correction | amendment and diagonal outline correction | amendment in embodiment. (A), (b), (c) is the example of an image which shows the effect of an embodiment.

Hereinafter, embodiments of the present disclosure will be described in detail based on the drawings.

FIG. 1 is a block diagram showing a configuration example of a contour correction apparatus according to this embodiment. The contour correction apparatus according to the present embodiment corrects the contour of an image represented by an input luminance signal so as to be sharper, for example.

The contour correction apparatus shown in FIG. 1 includes a horizontal / vertical contour correction unit 11 as a first correction unit, an oblique contour correction unit 12 as a second correction unit, an oblique degree detection unit 13, and a signal correction unit 20. ing. The horizontal / vertical contour correction unit 11 calculates a correction amount for performing contour correction in the horizontal direction and the vertical direction from the input luminance signal. Horizontal lines in the image are emphasized by contour correction in the vertical direction, and vertical lines are emphasized by contour correction in the horizontal direction. The oblique degree detection unit 13 detects the degree of obliqueness indicating how close an image is to an oblique line of a predetermined angle, that is, a so-called oblique line. In other words, the degree of obliqueness is an evaluation value that represents the degree to which an image approximates an oblique line with a predetermined angle. The oblique contour correction unit 12 calculates a correction amount for performing contour correction in a direction orthogonal to the oblique line of a predetermined angle from the input luminance signal. The predetermined angle at this time is preferably the same as the predetermined angle of the oblique line when the oblique degree is detected by the oblique degree detection unit 13.

The signal correction unit 20 adjusts the correction amount output from the horizontal / vertical contour correction unit 11 and the correction amount output from the oblique contour correction unit 12 in accordance with the oblique degree detected by the oblique degree detection unit 13. . Then, the input luminance signal is corrected using the adjusted correction amount and output as an output luminance signal. In other words, horizontal and vertical contour correction and oblique contour correction are blended according to the degree of obliqueness and applied to the luminance signal.

The horizontal line in the image is emphasized by the contour correction in the vertical direction, and the vertical line is emphasized by the contour correction in the horizontal direction. On the other hand, the diagonal line in the image is emphasized by both the contour correction in the vertical direction and the contour correction in the horizontal direction, so that only the horizontal and vertical contour correction is overcorrected. Therefore, the signal correction unit 20 decreases the effect of the correction amount output from the horizontal / vertical contour correction unit 11 and increases the effect of the correction amount output from the diagonal contour correction unit 12 as the degree of inclination increases. Further, the lower the degree of inclination, the greater the effect of the correction amount output from the horizontal / vertical contour correction unit 11 and the smaller the effect of the correction amount output from the oblique contour correction unit 12. Thereby, the oblique line in the image is appropriately corrected by the oblique contour correction without being overcorrected by the horizontal / vertical contour correction.

1 includes a first adjustment unit 14, a second adjustment unit 15, and a correction amount addition unit 16. The first adjustment unit 14 adjusts the correction amount output from the horizontal / vertical contour correction unit 11 according to the degree of inclination. The second adjustment unit 15 adjusts the correction amount output from the oblique contour correction unit 12 according to the degree of inclination. The correction amount addition unit 16 adds the correction amount after adjustment by the first adjustment unit 14 and the correction amount after adjustment by the second adjustment unit 15 to the input luminance signal. Here, the 1st adjustment part 14 adjusts the correction amount output from the horizontal / vertical outline correction | amendment part 11 so that it becomes small, so that an inclination degree is high, and it becomes large, so that an inclination degree is low. Further, the second adjustment unit 15 adjusts the correction amount output from the oblique contour correction unit 12 so that the correction amount increases as the degree of obliqueness increases and decreases as the degree of obliqueness decreases. Thereby, the horizontal / vertical contour correction and the diagonal contour correction are blended in accordance with the diagonal degree and applied to the luminance signal.

FIG. 2 is a diagram showing a specific configuration example of the contour correction apparatus according to the present embodiment. In the configuration of FIG. 2, the horizontal / vertical contour correction unit 11 of FIG. 1 is configured by a horizontal contour correction unit 11a and a vertical contour correction unit 11b, and the first adjustment unit 14 of FIG. 1 is configured by

multiplication units

14a and 14b. ing. Further, the second adjustment unit 15 in FIG. 1 is configured by a multiplication unit 15a. Further, the oblique degree detection unit 13 detects an oblique degree relating to an oblique line in the 45 degree direction (upward to the right) or 135 degree direction (upward to the left), and is normally in the range of 0 to 1 as an index indicating the oblique degree. Assume that the normalized value DD is calculated. The value DD is “1” when the diagonal degree is the highest and “0” when the diagonal degree is the lowest. Then, the

multipliers

14a and 14b multiply the correction amount by the value (1-DD), and the multiplier 15a multiplies the correction amount by the value DD. As a result, the correction amount is adjusted.

An example of signal processing in the oblique degree detection unit 13 will be described with reference to FIG. FIG. 3A shows a part of the image represented by the luminance signal, and includes an oblique line in the 45 degree direction. Here, it is assumed that a cumulative value of luminance differences of pixels that are continuous in the diagonal direction is used for the calculation of the diagonal degree. This is based on the premise that the pixels constituting the diagonal line have a small luminance difference.

In FIG. 3A, the oblique degree related to the oblique line in the 45 degree direction or the 135 degree direction is calculated using five consecutive pixels. Now, let the pixel marked with (3) be the pixel of interest. At this time, the luminance difference cumulative value DIFF45 in the 45 degree direction is
DIFF45
= ABS ((1)-(2)) + ABS ((2)-(3)) + ABS ((3)-(4)) + ABS ((4)-(5))
The luminance difference cumulative value DIFF135 in the 135 degree direction is
DIFF135
= ABS (AB) + ABS (B- (3)) + ABS ((3) -C) + ABS (CD)
It becomes. Note that ABS represents an absolute value calculation, and the numbers in parentheses and alphabets indicate the luminance value of the pixel.

Then, using a function f (x) as shown in FIG. 3B, a value DD is calculated from the smaller value of MIN (DIFF45, DIFF135), that is, DIFF45 and DIFF135. The function f (x) is a function in which the DD value approaches “1” as the MIN (DIFF45, DIFF135) decreases, and the DD value approaches “0” as the MIN (DIFF45, DIFF135) increases. Also,
DIFF45 <DIFF135
(That is, MIN (DIFF45, DIFF135) = DIFF45)
When it is, it is judged as a 45 degree diagonal line,
DIFF45> DIFF135
(That is, MIN (DIFF45, DIFF135) = DIFF135)
In this case, it is determined that the diagonal line is 135 degrees. The determination result is sent from the oblique degree detection unit 13 to the oblique contour correction unit 12.

In the example of the image in FIG. 3 (a), the value of DIFF45 becomes very small because a diagonal line rising to the right is included. Therefore, the value of DD is “1”. Further, since DIFF45 <DIFF135, it is determined as a 45-degree oblique line.

FIG. 4A shows another example of the image indicated by the luminance signal, which includes a diagonal line in the direction of 22.5 degrees, although it goes up to the right. In the case of FIG. 4A as well, since DIFF45 <DIFF135, it is determined that the line is an oblique line of 45 degrees. However, the value of DIFF 45 is larger than that in the case of FIG. That is, if DIFF 45 when a 45-degree diagonal line is included is DIFF 45 (45), and DIFF 45 when a 22.5-degree diagonal line is included is DIFF 45 (22.5),
DIFF45 (45) <DIFF45 (22.5)
It becomes. For this reason, as shown in FIG. 4B, by adjusting the function f (x), DD can be set to “0.5” when the diagonal line is 22.5 degrees, for example.

The shape of the function f (x) is not limited to that shown in FIGS. 3 and 4, and may have a curve, for example. Further, a known method may be used so that the shape of the function f (x) can be adjusted from the outside of the apparatus.

Next, signal processing in the oblique contour correcting unit 12 will be described with reference to FIG. Now, it is assumed that the oblique degree detection unit 13 determines that the image shown in FIG. At this time, the correction amount is calculated in a direction orthogonal to the 45 degree direction, that is, in the 135 degree direction. For example, assuming that the pixel marked with (3) is the pixel of interest, the correction amount is calculated using the luminance value of the pixel surrounded by the broken line in the figure.

Examples of processing performed here include oblique BPF and oblique transient correction. The oblique BPF is a method in which a BPF (Band Pass Filter) is applied in an oblique direction, here a 135 degree direction, and a chute is added to the edge. When a 5-tap filter with filter coefficients (a, b, c, d, e) is used, the filter output of the pixel of interest (3) is
a × A + b × B + c × (3) + d × C + e × D
It becomes. The oblique transient correction is a method in which the edge is sharpened by subtracting the correction signal from the input luminance signal in the oblique direction, here, in the direction of 135 degrees. Note that the contour correction in the oblique direction is not limited to these methods.

FIG. 6 is a diagram illustrating an example of a blending method of horizontal / vertical contour correction and oblique contour correction in the present embodiment. First, when the pattern of the image includes a horizontal line or a vertical line, the value DD indicating the degree of obliqueness is “0”. At this time, the value “1” is given to the

multipliers

14a and 14b, while the value “0” is given to the multiplier 15a. As a result, the correction amount added to the input luminance signal is
(Horizontal correction amount + vertical correction amount) × 1 + oblique correction amount × 0
= Horizontal correction amount + vertical correction amount.

In addition, when the image pattern includes a diagonal line of a predetermined angle, here 45 degrees or 135 degrees, the value DD indicating the degree of inclination is “1”. At this time, the value “0” is given to the

multipliers

14a and 14b, while the value “1” is given to the multiplier 15a. As a result, the correction amount added to the input luminance signal is
(Horizontal correction amount + vertical correction amount) × 0 + oblique correction amount × 1
= Oblique correction amount. That is, the contour correction in the horizontal direction and the vertical direction is not performed, and only the contour correction in the oblique direction is performed.

Further, when the image pattern includes a pattern close to a diagonal line at a predetermined angle, for example, a 22.5 degree diagonal line as shown in FIG. 4A, the value DD indicating the diagonal degree is “0”. .5 ". At this time, the value “0.5” is given to the

multipliers

14a and 14b, while the value “0.5” is given to the multiplier 15a. As a result, the correction amount added to the input luminance signal is
(Horizontal correction amount + vertical correction amount) × 0.5 + oblique correction amount × 0.5
It becomes. That is, the horizontal and vertical contour correction and the diagonal correction are performed with reduced intensity.

FIG. 7 shows the effect of this embodiment. As shown in FIG. 7B, the conventional method applies both horizontal contour correction and vertical contour correction to the input image including the 45-degree oblique line shown in FIG. The line is overcorrected, and jaggies and shoots are overemphasized and image quality is degraded. On the other hand, in this embodiment, as shown in FIG. 7C, the horizontal and vertical contour correction is not performed on the diagonal line, and only the diagonal contour correction is performed. Contour correction is realized.

In the present embodiment, the normalized value DD is calculated as an index value indicating the degree of inclination, and the correction amount is multiplied by the value DD and the value (1-DD). However, the correction according to the degree of inclination is performed. The method of adjusting the amount is not limited to this. For example, the inclination degree detection unit 13 may set a value to be multiplied by each correction amount according to the detected inclination degree. In this case, the relationship between the skew degree and the correction amount adjustment may be controlled from the outside of the apparatus. Alternatively, the oblique degree detection unit 13 gives the detected oblique degree to the first adjustment unit 14 and the second adjustment unit 15, and the first adjustment unit 14 and the second adjustment unit 15 respectively correct the correction amount according to the oblique degree. You may adjust it.

In the present embodiment, the angle of the oblique line when detecting the oblique degree is set to 45 degrees or 135 degrees. However, the present invention is not limited to this. Further, for example, a plurality of oblique contour correcting units 12 and oblique degree detecting units 13 may be provided, and a plurality of types of oblique contour correction may be executed in combination.

Further, the internal configuration of the signal correction unit 20 is not limited to that shown in FIGS. 1 and 2, and the horizontal / vertical contour correction and the diagonal contour correction are blended in accordance with the diagonal degree to obtain a luminance signal. Any configuration is applicable as long as it is applicable.

Further, all or a part of each unit shown in the present embodiment may be configured by a circuit or hardware, or may be realized by executing software by a processor.

Also, the contour correction device according to the present embodiment is used in, for example, an image processing device that displays an image or outputs an image to a monitor. Examples of the image processing device include a tablet, a smartphone, a TV device, and various video players.

In the present disclosure, the contour correction can be appropriately executed even when there is a diagonal line in the image, which is effective for displaying the image more clearly on the screen, for example, on a tablet or a smartphone.

11 Horizontal / vertical contour correction unit (first correction unit)
11a Horizontal contour correcting unit 11b Vertical contour correcting unit 12 Oblique contour correcting unit (second correcting unit)
13 Degree of Degree Detection Unit 14

First Adjustment Units

14a and 14b Multiplication Unit 15 Second Adjustment Unit 15a Multiplication Unit 16 Correction Amount Addition Unit 20 Signal Correction Unit

Claims

An outline correction apparatus for correcting the outline of an image represented by a luminance signal,
A first correction unit that calculates a first correction amount for performing contour correction in the horizontal direction and the vertical direction from the luminance signal;
A second correction unit that calculates a second correction amount for performing contour correction in a direction orthogonal to a diagonal line of a predetermined angle from the luminance signal;
An oblique degree detection unit for detecting an oblique degree, which represents the degree to which the image approximates the oblique line of the predetermined angle from the luminance signal;
A contour comprising: a signal correction unit that adjusts the first correction amount and the second correction amount according to the degree of inclination, and corrects the luminance signal using the corrected correction amount. Correction device.
The signal correction unit according to claim 1,
The higher the oblique degree, the smaller the effect of the first correction amount, and the larger the effect of the second correction amount, and the lower the oblique degree, the larger the effect of the first correction amount, the effect of the second correction amount. A contour correction apparatus characterized by reducing the size of the image.
In claim 1 or 2,
The contour correction apparatus, wherein the oblique degree detection unit calculates a luminance difference cumulative value in the direction of the predetermined angle, and calculates the oblique degree from the luminance difference cumulative value.
In any one of claims 1 to 3,
The signal correction unit is
A first adjustment unit that adjusts the first correction amount according to the degree of inclination;
A second adjustment unit that adjusts the second correction amount according to the degree of inclination;
A correction amount addition unit that adds the first correction amount after adjustment by the first adjustment unit and the second correction amount after adjustment by the second adjustment unit to the luminance signal;
The first adjustment unit adjusts the first correction amount so that the first correction amount decreases as the oblique degree increases and increases as the oblique degree decreases.
The contour correction apparatus according to claim 2, wherein the second adjustment unit adjusts the second correction amount so that the second correction amount increases as the oblique degree increases and decreases as the oblique degree decreases.
In claim 4,
The oblique degree detection unit outputs a value DD normalized to a range of 0 to 1 as the oblique degree,
The first adjustment unit multiplies the first correction amount by a value (1-DD);
The second adjustment unit multiplies the second correction amount by a value DD.
An image processing apparatus comprising the contour correction apparatus according to any one of claims 1 to 5.