KR20080093769A - Method and apparatus for enhancing visibility of image - Google Patents

Abstract

An apparatus and a method for enhancing the visibility of an image are provided to reduce the shoots and suppress bitmap jagging artifacts in an image signal, by setting ratios of peaking and crispening with respect to an input image. A high pass filter detects components of a high-frequency region of an input image by using filters having different coefficients. A shoot suppressor(203) removes shoot at an outer part of the input image by the smallest value of the detected components of the high-frequency region. A coring unit(204) cores a gain of a signal having no more than a predetermined level at the high-frequency region. A peaking and crispening ratio determiner(206) determines a ratio of peaking and a ratio of crispening based on the largest value of differential values with peripheral pixels centering on a corresponding pixel of the input image or information about the peripheral pixels. A multiplier(212) multiplies the ratio of peaking and the ratio of crispening by the components of the high-frequency region outputted from the shoot suppressor and the coring unit.

Description

Method and apparatus for enhancing visibility of image

1 is a conceptual diagram illustrating a conventional method for enhancing sharpness of a video signal.

2 is a block diagram of a device for enhancing image sharpness according to the present invention.

3 is a waveform diagram illustrating an operation of the chute suppressor of FIG. 2.

4 is a waveform diagram illustrating an operation of the coring unit of FIG. 2.

5 is a conceptual diagram illustrating an operation of the picking and crisping specific gravity determiner of FIG.

6 is a conceptual diagram illustrating an operation of a crisping gain detector of FIG. 2.

TECHNICAL FIELD The present invention relates to an image signal processing apparatus and method, and in particular, an image for suppressing overshoot / undershoot and bitmap jagging artifacts through signal processing according to edge-level. A device and method for enhancing the sharpness of a signal.

BACKGROUND ART In general, as HD image pickup apparatuses are widely used and image quality of broadcast signals is advanced, the importance of technology for improving the sharpness of outer information on a screen is increasing.

1 is a conceptual diagram illustrating a conventional method for enhancing sharpness of a video signal.

Referring to FIG. 1, in the related art, two filtering operations have been performed to enhance the sharpness. For the small outer information such as 101, the sharpness is increased by amplifying the high frequency as shown in 102. Accordingly, by increasing the high frequency, the frequency response such as 105 becomes larger in the frequency space, such as 106. Therefore, a peaking function is performed at a small transition edge such as 101.

In addition, for large edge information such as 103, sharpness is improved by reducing the transition time of the edge as shown in 104. Accordingly, by reducing the transition time of the outer edge, a frequency response such as 105 produces a higher frequency signal such as 107 in the frequency space. Therefore, a crispening function is performed at a large transition edge such as 103.

However, in performing the two filtering methods of the conventional sharpness enhancement method, the same processing is applied to the input pixel or the filtering is performed such as 102 in a specific section and the filtering such as 104 in another section. This method has the disadvantage that some artifacts can occur by performing redundant filtering on specific pixels.

An object of the present invention is to provide a method and apparatus for enhancing the sharpness of an image signal which reduces a chute and suppresses bitmap jagging artifacts by setting a peaking and crisping ratio for an input image. There is.

In order to solve the above technical problem, the present invention provides an image sharpening enhancement method,

Detecting high frequency region components of the input image using a filter having different coefficients, and suppressing the chute to a minimum value of the high frequency region components;

Coring a gain of a signal having a level below a predetermined range in the high frequency region component;

Setting and combining specific gravity for picking and crisping based on the outer characteristic information of the input image;

And giving a specific gravity to the combined peaking and crisping to the high frequency region component.

In order to solve the above other technical problem, the present invention provides an image sharpening enhancement device,

A high pass filter detecting high frequency region components of the input image by using filters having different coefficients;

A chute suppressor configured to remove a chute outside the image to a minimum value of components of different high frequency regions detected by the high pass filter;

A coring unit coring a gain of a signal having a level below a predetermined range in the high frequency region component;

A peaking and crisping specificity determining unit configured to determine a peaking and crisping specific gravity based on a maximum value or difference pixel information of the difference with surrounding pixels based on a corresponding pixel of the input image;

And a multiplier that multiplies the peaking specific gravity determined by the peaking and crisping specific gravity determining unit by a component of a high frequency region output from the chute suppressor and the coring unit.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

2 is a block diagram of a device for enhancing image sharpness according to the present invention.

The image sharpness enhancing apparatus of FIG. 2 includes a first and second high pass filters 201 and 202, a chute suppressor 203, a coiling unit 204, a local minimum and maximum detector 206, and a peaking and crisping ratio. The decision unit 206, the crisping gain detector 207, the first, second, and third multipliers 210, 211, and 212, and the adder 213 are included. The image sharpness enhancing apparatus of FIG. 2 may be replaced with a flowchart of the image sharpness enhancing method.

The first high pass filter unit 201 detects the component hpf1 of the high frequency region of the input image signal Y-in using a predetermined filter coefficient.

The second high pass filter unit 202 detects the component hpf2 of the high frequency region of the input image signal Y-in using a predetermined filter coefficient different from the first high pass filter unit 201.

The chute suppressor 203 takes the minimum values of the two high frequency components hpf1 and hpf2 detected by the first high pass filter 201 and the second high pass filter 202 to over / under the shot in the outer portion of the image. Suppress (over / under shoot) occurrences.

The coring unit 204 prevents boost-up of unnecessary components, that is, noise components when picking, in the component hpf2 of the high frequency region detected by the second high pass filter unit 202. The coring unit 204 removes and outputs these signals by setting the gain to "0" with respect to an input signal of a high frequency component having a level below a predetermined range. That is, the coring unit 204 attenuates the ringing phenomenon by removing a portion of the high frequency component that is the main cause of the ringing phenomenon in the video signal.

The local minimum and maximum value detector 205 detects minimum and maximum values between adjacent pixels based on the pixels being processed in the input image signal Y-in and analyzes which outer components the corresponding pixels are.

The peaking and crisping specificity determiner 206 determines and combines the peaking and crisping specificity c_ratio and p_ratio using the local minimum and maximum values detected by the local minimum and maximum value detection unit 205.

The crisping gain detector 207 detects a crisping gain c_gain using the local minimum and maximum values detected by the local minimum and maximum value detector 205. In other words, the crisping gain detector 207 detects at which position the pixel is located at the time of crisping.

The first multiplier 210 multiplies the crisping specific gravity c_ratio determined by the peaking and crisping specific gravity determiner 206 with the component hpf1 'of the high frequency region output from the chute suppressor 203 to improve sharpness. .

The second multiplier 211 suppresses bitmap jagging artifacts by multiplying a signal output from the first multiplier 210 by a crisping gain c_gain detected by the crisping gain detector 207.

The third multiplier 212 multiplies the component (hpf2 ') of the high frequency region output from the coring unit 204 by the picking specific gravity p_ratio determined by the peaking and crisping specific gravity determining unit 206.

The adder 213 adds the signal output from the second multiplier 211 and the signal output from the third multiplier 212 to output an image signal Y-out having improved clarity.

3 is a waveform diagram illustrating the operation of the chute suppressor 203 of FIG. 2.

Referring to FIG. 3, when the image signal 301 (Yin) input from the outer portion is high-pass filtered by the first high pass filter 201, it is shown as a filtering component such as 302. In addition, when the image signal 301 (Yin) input from the outer portion is high-pass filtered by the second high pass filter 202, it appears as a filtering component such as 303. Therefore, if we take the minimum value (Min (HPF1, | HPF2 |)) using two high-pass filter components, we can get the waveform like 304. 305 is an output video signal Yout after suppressing the chute. 306 is a simulation waveform performing the conventional chute suppression method, 307 is a simulation waveform performing the chute suppression method according to the present invention. Therefore, when comparing the existing 306 waveform and the 307 waveform of the present invention, it can be seen that the chute generation is significantly reduced in the outer image. The signal of the high frequency component hpf1 'in which the chute output from the chute suppressor 203 is suppressed may be expressed as in Equation (1).

hpf1 '= Min (hpf1, | hpf2 |) * hpf1

4 is a waveform diagram illustrating an operation of the coring unit 204 of FIG. 2.

Referring to FIG. 4, when a high frequency region is amplified using a high pass filter in a video signal, small noise signals are generated in the same response, and thus, small signals are not processed by a coring operation. 401 represents an original video signal and 402 represents a corrugated output signal. The first threshold th1 is a threshold for a section in which the high frequency amplification process is not performed in the input signal, and the second threshold th2 is a threshold for the upper limit of the high frequency amplification.

Therefore, the operation of the coring unit 204 is operated as follows.

IF | hpf | <th1, hpf '= 0

Else if ｜ hpf ｜> th2, hpf '= ± th2

Else hpf '= hpf ± th1

FIG. 5 is a conceptual diagram illustrating an operation of the picking and crisping specificity determiner 206 of FIG. 2.

The characteristics of the edges of the video signal are analyzed to determine the specific gravity of peaking and crisping. 501 denotes an input image pixel. The maximum value of a1 and a3 is obtained based on a2, and the peaking ratio and the crispening ratio according to which position is the maximum value based on the first threshold th1. ) Can be obtained.

Here, X1 and N1 are defined as in Equation 2.

X1 = max [| a2-a1 |, | a2-a3 |

N1 = min [| a2-a1 |, | a2-a3 |

Therefore, as shown in FIG. 5, if a maximum value exists on the left side of the first threshold th1, the peaking specificity increases as X1 increases, while the peaking specificity decreases and the crisping ratio increases as shown in 502.

On the other hand, if the maximum value is located to the right of the first threshold th1, the crisping specificity is reduced as in 503, but the peaking specificity is mapped to "0" as in 502, so picking is performed at the position where the difference value of adjacent pixels is large. I never do that. Peaking specific gravity is used for small edge enhancement, and crisping specific gravity is used for large edge enhancement.

In other words, the specific gravity for crisping is set in inverse proportion to the peaking ratio or by using the ratio of the maximum value of the difference value with the surrounding pixels.

FIG. 6 is a conceptual diagram illustrating an operation of the crisping gain detector 207 of FIG. 2.

Referring to FIG. 6, it is detected where the current pixel 601 is compared to the neighboring pixels 602 and 603 to obtain crisping gain (or intensity). As shown in FIG. 6, the minimum value N1 and the maximum value X1 are obtained for the current pixel 701 and the neighboring pixels 602 and 603 in the transition portion, and a gain value G1 corresponding to the ratio of the two values is obtained. ), The larger the G1, the larger the gain of the crisping gain and the sharper the edge of the signal.The smaller the G1, the lower the sharpening gain, which prevents the extreme edges. Can be prevented as much as possible.

Therefore, the operation of the crisping gain detector 207 can be expressed as follows.

If a2> a1 && a2 <a3 or If a2 <a1 && a2> a3 in the transition region

G1 = N1 / X1

If G1 ↑, then crispen gain ↑,

If G1 ↓, then crispen gain ↓.

The present invention is not limited to the above-described embodiment, and of course, modifications may be made by those skilled in the art within the spirit of the present invention.

The present invention can also be embodied as computer readable information on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, hard disk, floppy disk, flash memory, optical data storage device, and also carrier waves (for example, transmission over the Internet). It also includes the implementation in the form of. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable information is stored and executed in a distributed fashion.

As described above, according to the present invention, overshoot / undershoot and bitmap jagging artifacts can be suppressed by efficiently detecting a large outline and a detailed outline and performing different filtering.

Claims (7)

In the image sharpening enhancement method, Detecting high frequency region components of the input image using a filter having different coefficients, and suppressing the chute to a minimum value of the high frequency region components; Coring a gain of a signal having a level below a predetermined range in the high frequency region component; Setting and combining specific gravity for picking and crisping based on the outer characteristic information of the input image; And applying a specific gravity to the combined peaking and crisping to the high frequency region component. The image sharpness enhancement method of claim 1, wherein the specific gravity for picking and crisping is set based on a maximum value among the difference values with surrounding pixels or surrounding pixel information with respect to a pixel being processed. 2. The method of claim 1, wherein the step of assigning specific gravity for the peaking and crisping to the high frequency region component is multiplied by the peaking specific gravity or crisping specific gravity for the corresponding pixel and the high pass filter component. The image sharpness enhancement method of claim 1, wherein the specific gravity for the crisping is set in inverse proportion to the peaking ratio or by using a ratio of a maximum value among the difference values with surrounding pixels. The method of claim 1, further comprising setting a gain for the crisping to the high frequency region component by using a ratio between a maximum value and a minimum value among difference values with surrounding pixels for the specific pixel. An image sharpening enhancement method characterized by the above-mentioned. In the image sharpness enhancement device, A high pass filter detecting high frequency region components of the input image by using filters having different coefficients; A chute suppressor configured to remove a chute outside the image to a minimum value of components of different high frequency regions detected by the high pass filter; A coring unit coring a gain of a signal having a level below a predetermined range in the high frequency region component; A peaking and crisping specificity determining unit configured to determine a peaking and crisping specific gravity based on a maximum value or difference pixel information of the difference with surrounding pixels based on a corresponding pixel of the input image; And a multiplier that multiplies the peaking specific gravity determined by the peaking and crisping specific gravity determiner by a component of a high frequency region output from the chute suppressor and the coring unit. The image of claim 6, further comprising a crisping gain detector configured to set a gain for the crisping based on a ratio of the maximum value and the minimum value among the difference values with the surrounding pixels with respect to the specific pixel. Clarity Enhancing Method.

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