JP2004173065A - Image processing system, projector, program, information storage medium, and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing system or the like capable of performing gradation correction for reducing the emphasis of noise and the generation of a pseudo contour with a simpler configuration when processing an image containing a number of low-frequency components. <P>SOLUTION: The image processing system has a gradation correction section. The gradation correction section comprises an HPF 142 for outputting a high-frequency component from a luminance signal Y; an absolute value computing section 143 and a sum value computing section 144 for computing the sum value of an output value; a weighting factor computing section 145 that makes larger the weighting factor as the sum value becomes larger, and computing the weighting factor so that the weighting factor becomes the maximum value when the sum value is equal to or more than a specific value; a magnification computing section 152 for computing a magnification for the gradation correction, based on the weighting factor; and a multiplication section 153 for multiplying the luminance signal by the magnification for outputting an output luminance signal Y'. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image processing system for performing tone correction, a projector, a program, an information storage medium, and an image processing method.
[0002]
[Background Art]
There are various tone conversion processes for enhancing contrast in image processing technology. For example, a method using linear conversion, an exponential conversion represented by histogram flattening and gamma correction, a method using logarithmic conversion, and the like have been proposed. Furthermore, there is a method of determining a gradation conversion characteristic by using these methods and a statistical feature amount obtained from luminance distribution information of an image and the like, and further improving the image quality improving effect.
[0003]
For example, in Patent Document 1, based on a histogram flattening method, an average value, a minimum value, a mode value, a maximum value, a deviation coefficient (variance), a black area, and a white area of an input luminance signal are detected from a histogram. The cumulative start point and the cumulative stop point of the cumulative histogram are calculated, and the correction is performed using the cumulative histogram from the cumulative start point to the cumulative stop point normalized to the range of the minimum value to the maximum value. In this example, a degree of correction is adjusted by using a statistical feature obtained from a histogram of an input image to prevent excessive correction.
[0004]
[Patent Document 1]
JP-A-3-126377 [0005]
[Problems to be solved by the invention]
However, in the above example, since the spatial information of the image is not taken into account, when performing the gradation correction for enhancing the contrast of the image, the contrast according to the above example and the conventional example is applied to the image containing many low frequency components. When the emphasis processing is performed, noise emphasis or a pseudo contour may be generated.
[0006]
Specifically, for example, in a face image, a blue sky image, and the like, the skin color portion of the face, the blue portion of the blue sky, and the like include many low frequency components. When tone correction is performed on such an image as it is to enhance the contrast of the image, noise is enhanced or a pseudo contour is generated in the image. Further, in the above example, since the contrast correction processing is performed globally on the image, it is not possible to control the partial contrast correction processing.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a grayscale that reduces the emphasis of noise and the occurrence of false contours when processing an image containing a lot of low frequency components with a simpler configuration. An object of the present invention is to provide an image processing system, a projector, a program, an information storage medium, and an image processing method capable of performing correction.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, an image processing system according to the present invention includes a high frequency component output unit that outputs a high frequency component having a predetermined frequency or more from a luminance signal component included in an input video signal,
Sum value calculation means for calculating a sum value of output values by the high frequency component output means,
Weight coefficient calculating means for calculating a weight coefficient based on the sum value;
Magnification calculating means for calculating a magnification for gradation correction based on the weight coefficient;
Multiplying means for multiplying the luminance signal by the magnification and outputting an output luminance signal;
Including
The weighting factor calculating means increases the weighting factor as the sum value increases, and calculates the weighting factor such that the weighting factor becomes the maximum value when the sum value is equal to or greater than a predetermined value,
The magnification calculator is configured to calculate the magnification so that the weight coefficient is proportional to the magnification.
[0009]
The program according to the present invention is a computer-readable program,
Computer
High-frequency component output means for outputting a high-frequency component of a predetermined frequency or more from a luminance signal component included in the input video signal,
Sum value calculation means for calculating a sum value of output values by the high frequency component output means,
Weight coefficient calculating means for calculating a weight coefficient based on the sum value;
Magnification calculating means for calculating a magnification for gradation correction based on the weight coefficient;
Multiplying the luminance signal by the magnification, and functioning as a multiplication means for outputting an output luminance signal,
The weighting factor calculating means increases the weighting factor as the sum value increases, and calculates the weighting factor such that the weighting factor becomes the maximum value when the sum value is equal to or greater than a predetermined value,
The magnification calculator is configured to calculate the magnification so that the weight coefficient is proportional to the magnification.
[0010]
Further, an information storage medium according to the present invention is a computer-readable information storage medium, wherein a program for causing a computer to function as the above means is stored.
[0011]
Further, the image processing method according to the present invention outputs a high-frequency component of a predetermined frequency or more from a luminance signal component included in the input video signal,
Calculate the sum of the output values,
Based on the sum value, the larger the sum value is, the larger the weight coefficient is, and when the sum value is equal to or more than a predetermined value, the weight coefficient is calculated so that the weight coefficient becomes the maximum value,
Based on the weight coefficient, calculate the magnification for gradation correction so that the weight coefficient is proportional to the magnification,
Multiplying the luminance signal by the multiplication factor and outputting an output luminance signal;
[0012]
According to the present invention, the image processing system or the like increases the weighting factor as the sum of the high-frequency components is larger, and sets the maximum value of the weighting factor when the sum is equal to or greater than a predetermined value. The higher the proportion of the high-frequency component in the image, the more the contrast can be enhanced.
[0013]
Accordingly, the image processing system or the like can perform the image processing without enhancing the contrast as the ratio of the low frequency component in the image increases.
[0014]
Therefore, when processing an image containing many low-frequency components, an image processing system or the like can perform tone correction for reducing noise enhancement and generation of false contours.
[0015]
Further, according to the present invention, since the image processing system or the like does not set a value equal to or greater than the maximum value of the weight coefficient, it is possible to perform image processing without excessively enhancing contrast.
[0016]
Further, since the image processing system or the like does not need to generate and store the tone histogram of the image, tone correction can be performed with a simpler configuration than in the related art.
[0017]
Further, the image processing system and the projector, based on the luminance signal, edge detection means for detecting an edge,
A weighting factor update request signal generating means for generating a weighting factor update request signal when an edge is detected;
Including
The weight coefficient calculating means outputs an updated weight coefficient when the weight coefficient update request signal is received, and outputs an existing weight coefficient that has not been updated when the weight coefficient update request signal is not received. May be output.
[0018]
The program and the information storage medium may include a computer,
Edge detection means for detecting an edge based on the luminance signal,
When an edge is detected, a weight coefficient update request signal generating means for generating a weight coefficient update request signal is caused to function,
The weight coefficient calculating means outputs an updated weight coefficient when the weight coefficient update request signal is received, and outputs an existing weight coefficient that has not been updated when the weight coefficient update request signal is not received. May be output.
[0019]
Further, the image processing method detects an edge based on the luminance signal,
If an edge is detected, a weight coefficient update request signal is generated,
When calculating the weight coefficient, when the weight coefficient update request signal is received, the updated weight coefficient is output, and when the weight coefficient update request signal is not received, the existing weight that has not been updated is output. The coefficient may be output.
[0020]
According to this, the image processing system or the like can update the weight coefficient when detecting the edge of the image, and perform the tone correction without updating the weight coefficient when the edge of the image is not detected. it can.
[0021]
Accordingly, the image processing system or the like can perform the gradation correction according to the luminance configuring the image area, and thus can perform more appropriate gradation correction.
[0022]
Specifically, for example, in the case of an image composed of a blue sky and a mountain, an image processing system or the like performs tone correction that does not emphasize contrast so much in a blue sky region including many low frequency components, For a mountain region containing many high-frequency components, tone correction for enhancing contrast can be performed.
[0023]
The image processing system and the projector further include a storage unit configured to store a reference magnification value serving as a reference for the magnification,
Determining means for determining a feature of an image based on the luminance signal;
Reference magnification value calculating means for calculating the reference magnification value based on the determined image feature;
Including
The magnification calculating means may calculate the magnification based on the weight coefficient and the reference magnification value.
[0024]
The program and the information storage medium include a computer,
Storage means for storing a reference magnification value serving as a reference for the magnification,
Determining means for determining a feature of an image based on the luminance signal;
Based on the characteristics of the determined image, function as a reference magnification value calculating means for calculating the reference magnification value,
The magnification calculating means may calculate the magnification based on the weight coefficient and the reference magnification value.
[0025]
Further, the image processing method determines a feature of an image based on the luminance signal, updates the reference magnification value based on the determined feature of the image,
The magnification may be calculated based on the weight coefficient and the reference magnification value.
[0026]
According to this, the image processing system and the like, for example, by setting a small reference magnification value for an image containing many low-frequency components, and by setting a large reference magnification value for an image containing many high-frequency components , Appropriate gradation correction can be performed.
[0027]
Further, the image processing system and the projector may include a low-pass filter unit that extracts a low-frequency component from the luminance signal before inputting the luminance signal to the edge detection unit.
[0028]
Further, the program and the information storage medium may cause a computer to function as low-pass filter means for extracting a low-frequency component from the luminance signal before inputting the luminance signal to the edge detection means. .
[0029]
In the image processing method, a low-frequency component may be extracted from the luminance signal based on the luminance signal included in the input video signal before performing edge detection.
[0030]
According to this, since the image processing system or the like performs edge detection on an image that has passed through the low-pass filter, the edge detection accuracy can be improved. Thus, the image processing system or the like can increase the accuracy of region division by edge detection.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a case where the present invention is applied to an image processing system that receives an RGB signal, which is a kind of video signal, and performs gradation correction of luminance (also referred to as “luminance value” or “luminance level”) of each signal. An example will be described with reference to the drawings. The embodiments described below do not limit the contents of the invention described in the claims. In addition, all of the configurations described in the following embodiments are not necessarily indispensable as means for solving the invention described in the claims.
[0032]
(Description of the whole system)
Hereinafter, a case where the present invention is applied to an image processing system of a liquid crystal projector will be described as an example.
[0033]
FIG. 1 is a schematic explanatory diagram of a projector 20 according to an example of the present embodiment.
[0034]
A projector 20 provided substantially in front of the screen 10 projects various images.
[0035]
The presenter 30 gives a presentation to a third party while pointing a desired position of an image in the image display area 12 on the screen 10 with a spotlight projected from the laser pointer 50.
[0036]
For example, when the projector 20 performs normal contrast enhancement processing on an image including many low-frequency components such as a face image or a blue sky and projects the image, noise is enhanced or a pseudo contour is generated in the projected image. In some cases.
[0037]
Therefore, in the present embodiment, the projector 20 performs the edge detection processing of the image to divide the area, grasps the degree to which the high frequency component is included in each area, and performs the gradation correction according to the high frequency component included in the image. I do.
[0038]
Next, functional blocks of an image processing unit of the projector 20 for realizing such a function will be described.
[0039]
FIG. 2 is a functional block diagram of an image processing unit according to an example of the present embodiment.
[0040]
An image processing unit in the projector 20 includes an RGB-YUV conversion unit 110 that converts an RGB signal that is an input video signal into a YUV signal, a correction unit 120 that corrects a YUV signal, and a corrected Y′U′V ′ signal. Is converted to an R′G′B ′ signal, and an image projection unit 190 that projects an image based on the R′G′B ′ signal.
[0041]
Further, the correction unit 120 includes a gradation correction unit 140 that performs gradation correction by correcting the input luminance signal Y and outputs a corrected luminance signal Y ′.
[0042]
The image projection unit 190 includes a spatial light modulator 192, a driving unit 194 that drives the spatial light modulator 192 based on the R′G′B ′ signal, and a light source 196 that outputs light to the spatial light modulator 192. And a lens 198 for projecting the light modulated by the spatial light modulator 192.
[0043]
In this manner, the projector 20 performs the gradation correction and projects the image.
[0044]
Here, the configuration of the tone correction unit 140 will be described.
[0045]
FIG. 3 is a functional block diagram of the gradation correction unit 140 according to an example of the present embodiment.
[0046]
The tone correction unit 140 removes noise and further functions as a low-pass filter (LPF) 141 that functions as a low-pass filter unit that increases the accuracy of area division by edge detection. It includes an HPF (High Pass Filter) 142 functioning as an output high frequency component output unit, an absolute value operation unit 143 for calculating an absolute value of the output, and a total value operation unit 144 for calculating a total value of the absolute values. It is composed of
[0047]
Further, the gradation correction unit 140 includes an edge detection unit 146 that detects an edge based on the luminance signal that has passed through the LPF 141, a pixel count unit 147 that counts the number of pixels forming an image, an edge detection status and the number of pixels. And a weight coefficient update request signal generation section 148 that generates a weight coefficient update request signal when a predetermined condition is satisfied based on
[0048]
Further, the gradation correction unit 140 includes a weight coefficient calculation unit 145.
[0049]
The weight coefficient calculation unit 145 calculates a weight coefficient for gradation correction based on the sum value from the sum value calculation unit 144. Also, the weight coefficient calculating section 145 outputs a new weight coefficient from the weight coefficient calculating section 145 only when receiving the weight coefficient updating request signal from the weight coefficient updating request signal generating section 148, and outputs the weight coefficient updating request signal. Is not received, the new weighting coefficient is not output from the weighting coefficient calculator 145, and the weighting coefficient output last time is output as it is.
[0050]
Further, the gradation correction unit 140 includes an LUT (Look Up Table) update determination unit 149 that functions as a determination unit that determines the characteristics of the image based on the luminance signal, and a gradation correction unit 149 based on the determined image characteristics. The configuration includes an LUT calculation unit 150 that functions as a reference magnification value calculation unit that calculates a reference magnification value serving as a reference of the magnification, and an LUT storage unit 151 that stores the reference magnification value.
[0051]
Note that the LUT update determination unit 149 transmits an LUT update request signal to the LUT calculation unit 150 according to a predetermined rule. Here, the predetermined rule includes, for example, a rule based on a change in a feature amount such as an APL (Average Picture Level: an average value of luminance values in a predetermined period) derived from an image, and an interrupt periodically transmitted from the processor. A rule based on signal reception may be used. When receiving the LUT update request signal from the LUT update determination unit 149, the LUT calculation unit 150 calculates a reference magnification value that is a reference of a magnification for gradation correction.
[0052]
Further, the gradation correction unit 140 calculates a magnification for gradation correction based on the weighting coefficient and the reference magnification value, and a multiplication of the input luminance signal Y and the magnification to output a luminance signal. And a multiplication unit 153 that outputs Y ′.
[0053]
Next, the flow of gradation correction using these units will be described.
[0054]
FIG. 4 is a flowchart of gradation correction according to an example of the present embodiment.
[0055]
First, the HPF 142 extracts and outputs a high-frequency component from the luminance signal (Step S2).
[0056]
Then, the absolute value calculator 143 calculates the absolute value of the output value (Step S3).
[0057]
Then, the sum value calculation unit 144 calculates the sum value of the absolute values (step S4).
[0058]
Further, the gradation correction section 140 performs a weight coefficient update request process (step S5) and a weight coefficient calculation process (step S6) to obtain a weight coefficient used at the time of gradation correction.
[0059]
Here, the weight coefficient update request processing (step S5) will be described in more detail.
[0060]
FIG. 5 is a flowchart of a weight coefficient update request process according to an example of the present embodiment.
[0061]
The edge detection unit 146 detects the edge (boundary) of the area from the low luminance signal component that has passed through the LPF 141, and the pixel count unit 147 counts the number of pixels based on the luminance signal (Step S21).
[0062]
The weight coefficient update request signal generator 148 determines whether an edge has been detected by the edge detector 146 (step S22).
[0063]
When an edge is detected by the edge detection unit 146, the weight coefficient update request signal generation unit 148 determines whether the pixel count value (pixel count) counted from the previous edge detection is greater than the threshold th1. (Step S23). Then, when the pixel count value is greater than the threshold th1, the weight coefficient update request signal generation unit 148 generates a weight coefficient update request signal High (step S25).
[0064]
The reason why such processing is performed is to remove the influence of erroneous edge detection in a region containing a large amount of high-frequency components.
[0065]
If no edge is detected, the weight coefficient update request signal generation section 148 determines whether or not the pixel count value of the pixel count section 147 has exceeded the number of pixels in the capture area (step S24).
[0066]
The weight coefficient update request signal generating section 148 generates a weight coefficient update request signal High when the pixel count value of the pixel count section 147 exceeds the number of pixels in the capture area (step S25).
[0067]
Note that the weight coefficient update request signal generation unit 148 generates the weight coefficient update request signal Low when no edge is detected and the pixel count value is equal to or less than the number of pixels in the capture area.
[0068]
That is, the weight coefficient update request signal generator 148 issues a weight coefficient update request only when an edge is detected or an image is switched.
[0069]
This allows the projector 20 to divide the image into a plurality of regions by edge detection and perform different gradation corrections for each region where the image is changing.
[0070]
Next, the weight coefficient calculation processing (step S6) will be described in more detail.
[0071]
FIG. 6 is a flowchart of a weight coefficient calculation process according to an example of the present embodiment.
[0072]
The weight coefficient calculation unit 145 determines whether the weight coefficient update request signal from the weight coefficient update request signal generation unit 148 is High (step S31).
[0073]
When the weighting factor update request signal is not High, that is, when the image is not switched, the weighting factor calculation unit 145 outputs the weighting factor z used so far as it is.
[0074]
On the other hand, when the weight coefficient update request signal is High, the weight coefficient calculator 145 determines whether the sum HPFsum by the sum calculator 144 is less than the threshold HPFth (step S32).
[0075]
When the total value HPFsum is equal to or greater than the threshold value HPFth, the weighting coefficient calculator 145 sets the threshold value HPFth as the total value HPFsum (step S33).
[0076]
On the other hand, when the total value HPFsum is smaller than the threshold value HPFth, the weighting coefficient calculator 145 uses the total value HPFsum as it is.
[0077]
Then, the weighting coefficient calculator 145 calculates a value obtained by dividing the sum HPFsum by the threshold HPFth, and applies this value as the weighting coefficient z (step S34).
[0078]
That is, the weight coefficient calculating unit 145 outputs the newly calculated weight coefficient z only when there is a request for updating the weight coefficient, and outputs the previously calculated weight coefficient z without changing the weight coefficient z when there is no request for updating the weight coefficient. The weight coefficient z thus output is output as it is.
[0079]
FIG. 7 is a diagram illustrating characteristics of the weight coefficient z according to an example of the present embodiment.
[0080]
As described above, when the sum value HPFsum is equal to or greater than the threshold value HPFth, the weighting coefficient calculation unit 145 sets the threshold value HPFth as the sum value HPFsum, and therefore, as shown in FIG. The value becomes 0 or more and 1 or less, and is proportional to the total value HPFsum.
[0081]
That is, when the sum total value HPFsum is equal to or larger than the threshold value HPFth, the weighting coefficient becomes 1 which is the maximum value, and a value exceeding 1 is not set. Processing can be performed.
[0082]
Further, as shown in FIG. 4, the LUT update determination unit 149 detects a change in the feature amount of the image due to APL or the like based on the luminance signal (step S7), and determines whether it is necessary to update the LUT. (Step S8).
[0083]
If the LUT needs to be updated, the LUT calculation unit 150 obtains the reference magnification value L stored in the LUT storage unit 151 by a linear or non-linear calculation, and updates the LUT (step S9).
[0084]
The magnification calculator 152 calculates a magnification L ′ for gradation correction based on the weight coefficient z and the reference magnification value L (step S10).
[0085]
For example, the following expression can be applied as the operation expression.
[0086]
L ′ = 1.0 + z (L−1.0)
By this calculation, a magnification substantially close to the reference magnification value L is applied to an image having many high-frequency components and a weight coefficient z close to 1, and to an image having a small high-frequency component and a weight coefficient z close to 0. A magnification close to 1.0 is applied, and the effect of enhancing the contrast of the image is suppressed.
[0087]
Then, the multiplication unit 153 multiplies the input luminance signal Y by the magnification L ′ and outputs an output luminance signal Y ′ (step S11).
[0088]
Note that, for example, the following can be applied as hardware for realizing the function of each unit of the image processing system described above.
[0089]
FIG. 8 is a hardware block diagram of the projector 20 according to an example of the present embodiment.
[0090]
For example, the RGB-YUV conversion unit 110 and the YUV-RGB conversion unit 130 include, for example, an image processing circuit 970, and the pixel count unit 147, and the LUT storage unit 151 include, for example, a RAM 950, an image processing circuit 970, and the like. The section 143, the sum value calculation section 144, the weight coefficient calculation section 145, the weight coefficient update request signal generation section 148, the LUT update determination section 149, the LUT calculation section 150, the magnification calculation section 152, for example, the CPU 910 and the multiplication section 153 The spatial light modulator 192, such as a multiplier, can be realized using, for example, a liquid crystal panel 920, a ROM 960 storing a liquid crystal light valve driving driver for driving the liquid crystal panel 920, or the like.
[0091]
These units can exchange information with each other via a system bus 980.
[0092]
These units may be realized by hardware like a circuit, or may be realized by software like a driver.
[0093]
Furthermore, the computer may realize the function of the tone correction unit 140 by reading a program from the information storage medium 900 storing a program for causing the computer to function as the tone correction unit 140.
[0094]
As such an information storage medium 900, for example, a CD-ROM, a DVD-ROM, a ROM, a RAM, an HDD, and the like can be applied, and the method of reading the program may be a contact method or a non-contact method. Good.
[0095]
In addition, instead of the information storage medium 900, it is also possible to realize each function described above by downloading a program or the like for realizing each function described above from a host device or the like via a transmission path.
[0096]
As described above, according to the present embodiment, projector 20 increases the weighting factor as the sum of the high-frequency components increases, and sets the maximum value of the weighting factor when the sum is equal to or greater than the predetermined value. By doing so, the contrast can be enhanced more easily as the proportion of the high-frequency component in the image increases.
[0097]
Accordingly, the projector 20 can perform the image processing without enhancing the contrast as the ratio of the low-frequency component in the image increases.
[0098]
Therefore, when processing an image containing many low-frequency components, the projector 20 can perform tone correction for reducing noise enhancement and generation of false contours.
[0099]
Further, since the projector 20 does not set a value equal to or greater than the maximum value of the weight coefficient, it is possible to perform image processing without excessively enhancing contrast.
[0100]
Further, since the projector 20 does not need to generate and store a tone histogram of an image, tone correction can be performed with a simpler configuration than in the related art.
[0101]
In addition, the projector 20 can update the weight coefficient when detecting an edge of the image, and perform gradation correction without updating the weight coefficient when detecting no edge of the image.
[0102]
Thereby, the projector 20 can perform the gradation correction according to the luminance configuring the image area, and thus can perform more appropriate gradation correction.
[0103]
Specifically, for example, in the case of an image composed of a blue sky and a mountain, the projector 20 performs a gradation correction that does not emphasize contrast so much in a blue sky region that includes many low frequency components, and Can be subjected to gradation correction for enhancing the contrast in the mountain region including many.
[0104]
In addition, the projector 20 sets the reference magnification value to a small value for an image containing many low-frequency components, and sets the reference magnification value to a large value for an image containing many high-frequency components. Corrections can be made.
[0105]
Furthermore, since the projector 20 performs edge detection on an image that has passed through the LPF 141, the edge detection accuracy can be improved. Thereby, the projector 20 can increase the accuracy of region division by edge detection.
[0106]
(Modification)
The preferred embodiment to which the present invention is applied has been described above, but the application of the present invention is not limited to the above-described embodiment.
[0107]
For example, the functions of the LPF 141 and the HPF 142 may be realized by combining a band pass filter (BPF) that passes only a predetermined band instead of the LPF 141 and the HPF 142.
[0108]
Further, the function of the above-described gradation correction unit 140 may be distributed to a plurality of devices to perform gradation correction.
[0109]
The image processing system that executes the above-described gradation correction is not limited to a liquid crystal projector such as the projector 20, and for example, a projector using a DMD (Digital Micromirror Device), a CRT (Cathode Ray Tube), and a PDP (Plasma Display). Panels, FEDs (Field Emission Display), ELs (Electro Luminescence), direct-view type liquid crystal display devices, and other various display devices. DMD is a trademark of Texas Instruments of the United States.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory diagram of a projector according to an example of an embodiment.
FIG. 2 is a functional block diagram of an image processing unit according to an example of the present embodiment.
FIG. 3 is a functional block diagram of a gradation correction unit according to an example of the embodiment.
FIG. 4 is a flowchart of gradation correction according to an example of the embodiment.
FIG. 5 is a flowchart of a weight coefficient update request process according to an example of the embodiment;
FIG. 6 is a flowchart of a weight coefficient calculation process according to an example of the embodiment.
FIG. 7 is a diagram illustrating characteristics of a weight coefficient z according to an example of the present embodiment.
FIG. 8 is a hardware block diagram of a projector according to an example of the embodiment.
[Explanation of symbols]
140 tone correction section, 141 LPF (low-pass filter means), 142 HPF (high-frequency component output means), 143 absolute value calculation section (sum value calculation means), 144 sum value calculation section (sum value calculation means), 145 weight Coefficient calculation unit, 146 edge detection unit, 147 pixel count unit, 148 weight coefficient update request signal generation unit, 149 LUT update determination unit (determination unit), 150 LUT calculation unit (reference magnification value calculation unit), 151 LUT storage unit , 152 magnification operation unit, 153 multiplication unit, 900 information storage medium

Claims (14)

High-frequency component output means for outputting a high-frequency component of a predetermined frequency or more from a luminance signal component included in the input video signal,
Sum value calculation means for calculating a sum value of output values by the high frequency component output means,
Weight coefficient calculating means for calculating a weight coefficient based on the sum value;
Magnification calculating means for calculating a magnification for gradation correction based on the weight coefficient;
Multiplying means for multiplying the luminance signal by the magnification and outputting an output luminance signal;
Including
The weighting factor calculating means increases the weighting factor as the sum value increases, and calculates the weighting factor such that the weighting factor becomes the maximum value when the sum value is equal to or greater than a predetermined value,
The image processing system according to claim 1, wherein the magnification calculator calculates the magnification so that the weighting coefficient is proportional to the magnification. In claim 1,
Edge detection means for detecting an edge based on the luminance signal,
A weighting factor update request signal generating means for generating a weighting factor update request signal when an edge is detected;
Including
The weight coefficient calculating means outputs an updated weight coefficient when the weight coefficient update request signal is received, and outputs an existing weight coefficient that has not been updated when the weight coefficient update request signal is not received. An image processing system characterized by outputting. In any one of claims 1 and 2,
Storage means for storing a reference magnification value serving as a reference for the magnification,
Determining means for determining a feature of an image based on the luminance signal;
Reference magnification value calculating means for calculating the reference magnification value based on the determined image feature;
Including
The image processing system according to claim 1, wherein the magnification calculating means calculates the magnification based on the weight coefficient and the reference magnification value. In any one of claim 2 and claim 3 dependent on claim 2,
An image processing system comprising: a low-pass filter unit that extracts a low-frequency component from the luminance signal before inputting the luminance signal to the edge detection unit. A projector comprising the image processing system according to claim 1. A computer readable program,
Computer
High-frequency component output means for outputting a high-frequency component of a predetermined frequency or more from a luminance signal component included in the input video signal,
Sum value calculation means for calculating a sum value of output values by the high frequency component output means,
Weight coefficient calculating means for calculating a weight coefficient based on the sum value;
Magnification calculating means for calculating a magnification for gradation correction based on the weight coefficient;
Multiplying the luminance signal by the magnification, and functioning as a multiplication means for outputting an output luminance signal,
The weighting factor calculating means increases the weighting factor as the sum value increases, and calculates the weighting factor such that the weighting factor becomes the maximum value when the sum value is equal to or greater than a predetermined value,
The program, wherein the magnification calculating means calculates the magnification so that the weight coefficient is proportional to the magnification. In claim 6,
Computer
Edge detection means for detecting an edge based on the luminance signal,
When an edge is detected, a weight coefficient update request signal generating means for generating a weight coefficient update request signal is caused to function,
The weight coefficient calculating means outputs an updated weight coefficient when the weight coefficient update request signal is received, and outputs an existing weight coefficient that has not been updated when the weight coefficient update request signal is not received. A program characterized by outputting. In any one of claims 6 and 7,
Computer
Storage means for storing a reference magnification value serving as a reference for the magnification,
Determining means for determining a feature of an image based on the luminance signal;
Based on the characteristics of the determined image, function as a reference magnification value calculating means for calculating the reference magnification value,
The program, wherein the magnification calculating means calculates the magnification based on the weighting coefficient and the reference magnification value. In any one of claim 7 and claim 8 dependent on claim 7,
A program for causing a computer to function as low-pass filter means for extracting a low-frequency component from the luminance signal before inputting the luminance signal to the edge detection means. An information storage medium storing the program according to claim 6. Outputting a high frequency component of a predetermined frequency or more from a luminance signal component included in the input video signal,
Calculate the sum of the output values,
Based on the sum value, the larger the sum value is, the larger the weight coefficient is, and when the sum value is equal to or more than a predetermined value, the weight coefficient is calculated so that the weight coefficient becomes the maximum value,
Based on the weight coefficient, calculate the magnification for gradation correction so that the weight coefficient is proportional to the magnification,
An image processing method comprising multiplying the luminance signal by the magnification and outputting an output luminance signal. In claim 11,
Detecting an edge based on the luminance signal,
If an edge is detected, a weight coefficient update request signal is generated,
When calculating the weight coefficient, when the weight coefficient update request signal is received, the updated weight coefficient is output, and when the weight coefficient update request signal is not received, the existing weight that has not been updated is output. An image processing method characterized by outputting a coefficient. In any one of claims 11 and 12,
Based on the luminance signal, determine the characteristics of the image, based on the determined characteristics of the image, update the reference magnification value,
An image processing method, wherein the magnification is calculated based on the weight coefficient and the reference magnification value. In any one of claims 12 and 13 dependent on claim 12,
An image processing method, comprising: extracting a low-frequency component from a luminance signal before performing edge detection based on the luminance signal included in the input video signal.

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