JP5072742B2 - Image processing apparatus and image processing method - Google Patents

Description

  The present invention relates to an image processing apparatus and an image processing method for correcting the gradation of an image signal to be displayed according to the characteristics of a display apparatus that displays an image.

  Display devices such as LCD (Liquid Crystal Display) monitors, PDP (Plasma Display Panel) monitors, and organic EL (Electro Luminescence) monitors are inherent between the gradation of the input image signal and the luminance of the image to be displayed. It has an input / output relationship (hereinafter referred to as gradation characteristics). By having such gradation characteristics, an image having brightness characteristics different from the input image signal may be displayed on the display device.

  Therefore, the display device performs gamma correction on each tone value of the input image in accordance with a tone characteristic (hereinafter referred to as a gamma curve) indicating the relationship between the tone value of the input image and the luminance value of the output image. The relationship between the input gradation and the output luminance is corrected. With such a configuration, the display device can display an image having substantially the same brightness characteristics as the input image.

  In Patent Document 1, a plurality of gamma curves are prepared in advance considering the gradation characteristics of the display device, and the gamma curve (gamma correction table) is changed according to the gradation histogram of the image signal (video signal) to be displayed. An apparatus is disclosed. By using such an apparatus, it is possible to perform gamma correction processing based on an appropriate gamma curve corresponding to the characteristics of the gradation value of the input image signal.

In Patent Document 2, the presence or absence of gradation skip in the low gradation part and the degree of gradation collapse in the low gradation part are detected from the histogram indicating the gradation distribution of the input video signal, and gamma correction is performed according to the detection result. An apparatus for determining whether or not to perform the determination and determining the gamma correction amount is disclosed. By using such an apparatus, it is possible to determine the gamma correction amount according to the presence / absence of gradation skip and the degree of gradation collapse, and it is possible to perform the optimum gamma correction processing for any input image.
Japanese Patent Laid-Open No. 06-230760 JP-A-10-126619

  However, since the gamma curve (gamma correction table) prepared in advance is automatically changed in the apparatuses disclosed in Patent Documents 1 and 2, the image quality desired by the user is not necessarily realized. In addition, there is a problem that the user cannot select an arbitrary gamma curve in order to realize the desired image quality.

  The present invention has been made in view of such circumstances, and an object of the present invention is to set information used for correction processing for realizing user-preferred image quality without performing complicated operations. It is an object to provide an image processing apparatus and an image processing method capable of performing the above.

An image processing apparatus according to the present invention is based on a correction unit that corrects an input tone of an input image signal to an output tone corresponding to the input tone and outputs the image signal output from the correction unit. An image processing apparatus comprising display control means for displaying an image on a display device, generating means for generating a gradation distribution indicating the number of pixels for each input gradation of pixels included in the image signal, and the generating means In the determining means for determining the range of the input gradation in which the corresponding output gradation can be changed based on the generated gradation distribution, the gradation distribution generated by the generating means, and the correction processing performed by the correcting means Display screen information generating means for generating display screen information for displaying a correction characteristic indicating the relationship between the input gradation and the output gradation, and a receiving means for receiving the change of the output gradation within the range determined by the determining means and, hand with receiving A adding means that the changes indicating a change has been accepted, added to the correction characteristic in the display screen based on the display screen information in which the display screen information generating means has generated, the display control means, the adding means is the The display screen to which a change point has been added is displayed on the display device, and when the accepting unit accepts a plurality of changes, the adding unit displays a change point indicating each change accepted by the accepting unit. The correction means adds the input gradation of the image signal based on the output gradation received by the accepting means according to the input gradation. It is characterized by being configured so as to correct the tone.

According to the present invention, in a pixel included in an image signal, a gradation distribution indicating the number of pixels for each input gradation is generated, and an input whose corresponding output gradation can be changed based on the generated gradation distribution. A gradation range is determined, and an output gradation change is accepted within the determined range. Further, according to the present invention, the image signal is corrected based on the output gradation for which the change has been accepted, and an image based on the corrected image signal is displayed on the display device. Therefore, the user can arbitrarily set the output gradation corresponding to the input gradation, and correction processing based on the set output gradation is possible. In addition, since the range in which the output gradation can be changed is automatically determined based on the gradation distribution of the image signal, the user can save time and effort to determine in which range the output gradation should be changed. Operation can be simplified. In addition, the gradation distribution generated from the image signal and the correction characteristic indicating the relationship between the input gradation and the output gradation in the correction process are displayed on the display device, and the user sets a change to the correction characteristic (gamma curve). In this case, a change point indicating the set change is added to the correction characteristic and displayed. Therefore, the user can set a change to the correction characteristic (gamma curve) while referring to the gradation distribution, and can improve the operability in the change operation. Further, when the user sets a plurality of changes to the correction characteristics, it is possible to improve the operability by displaying the change points indicating the respective changes in different colors.

  The image processing apparatus according to the present invention is characterized in that the determining means is configured to determine a range including pixels having a predetermined ratio with respect to the total number of pixels included in the image signal. To do.

  According to the present invention, by appropriately determining a range in which the user can arbitrarily change the output gradation, it is possible to accept a change to a gamma curve (output gradation) that can realize high image quality by gamma correction processing. This makes it possible to avoid changing the gamma curve within a range that does not affect the image signal.

  In the image processing apparatus according to the present invention, the display control unit causes the display device to display a display screen based on the display screen information generated by the display screen information generation unit so as to be superimposed on an image based on the image signal. It is comprised by these.

  According to the present invention, the display screen that displays the gradation distribution generated from the image signal and the correction characteristic indicating the relationship between the input gradation and the output gradation in the correction process is displayed by being superimposed on the image based on the image signal. Display on the device. Therefore, the user can simultaneously check the output gradation (correction characteristics) arbitrarily set and the image subjected to the correction processing based on the correction characteristics. In addition, the user can confirm the influence of the correction process based on the correction characteristic set by the user, and can make further changes after the confirmation.

  The image processing apparatus according to the present invention is characterized in that the display screen information generation means is configured to enlarge and display the gradation distribution and the correction characteristics within the range determined by the determination means.

  According to the present invention, the gradation distribution and the correction characteristics in the display screen are enlarged and displayed in the changeable input gradation range determined based on the gradation distribution. Therefore, it is possible to display the gradation distribution and correction characteristics in a range that can be arbitrarily set by the user in an easy-to-see manner.

  The image processing apparatus according to the present invention generates a look-up table in which the input gradation and the output gradation in the correction process performed by the correction unit are associated with each other based on the output gradation received by the reception unit. Means and storage means for storing the generated lookup table, and the correction means corrects the input gradation of the image signal based on the lookup table stored in the storage means. It is configured.

  According to the present invention, a lookup table in which an input tone and an output tone in a correction process are associated with each other is generated based on an output tone that has been changed by a setting from a user, and the generated lookup table Is stored in the storage means. Then, the input gradation of the image signal is corrected based on the lookup table stored in the storage means, and an image based on the corrected image signal is displayed on the display device. Therefore, by performing the correction process using the lookup table, the process can be simplified and the processing time can be shortened.

An image processing method according to the present invention corrects an input gradation of an input image signal to an output gradation corresponding to the input gradation, and causes an image based on the corrected image signal to be displayed on a display device. The step of generating a gradation distribution indicating the number of pixels for each input gradation of the pixels included in the image signal, and an input floor on which the corresponding output gradation can be changed based on the generated gradation distribution. A step of determining a range of tones, and a step of generating display screen information for displaying the generated gradation distribution and a correction characteristic indicating a relationship between an input gradation and an output gradation in a correction process performed on the image signal When the step of accepting a change of the output tone within the determined range, the additional steps of the changes indicating a change has been accepted, added to the correction characteristic in the display screen based on the generated said display screen information, before A step of displaying the display screen obtained by adding the changes to the display device, based on the output gradation of accepting the changes, the input gray level of the image signal, correcting the output gradation corresponding to the input grayscale The adding step is characterized in that, when a plurality of changes are received, the changing points indicating the received changes are added in different colors .

  According to the present invention, the user can arbitrarily set the output gradation corresponding to the input gradation, and correction processing based on the set output gradation can be performed. In addition, since the range in which the output gradation can be changed is automatically determined based on the gradation distribution of the image signal, the user can save time and effort to determine in which range the output gradation should be changed. Operation can be simplified.

  In the present invention, since the user can arbitrarily set the output gradation corresponding to the input gradation of the image signal, the image quality desired by the user can be obtained by performing such gradation characteristic correction processing on the image signal. Can be realized. Further, since the range that can be arbitrarily set by the user is automatically determined based on the tone distribution in the image signal, the user can change (set) the output tone corresponding to the input tone within the determined range. The operation procedure by the user can be simplified, and the operation burden can be reduced.

  Hereinafter, an image processing apparatus and an image processing method according to the present invention will be described with reference to the drawings illustrating a liquid crystal television as an embodiment thereof. The image processing apparatus of the present invention is not limited to a liquid crystal television. For example, display apparatuses such as a liquid crystal display (LCD monitor), a plasma display (PDP monitor), an organic EL display (organic EL monitor), and these display apparatuses. The present invention can be applied to an information processing apparatus such as a connectable personal computer (PC).

  FIG. 1 is a block diagram showing a configuration example of a liquid crystal television according to this embodiment. Note that reference numerals in FIG. 1 indicate signals such as broadcast signals, video signals (image signals), audio signals, EPG (Electronic Program Guide) signals, control signals, and various information flows. The liquid crystal television 1 of this embodiment includes a tuner 10, an external input unit 11, an AV selector 12, a separation unit 13, an audio decoder 14, a video decoder 15, an EPG decoder 16, an audio processing unit 17, a speaker 18, a video processor 19, and a liquid crystal. A module 20, a microcomputer 21, a memory 22, an operation unit 23, an OSD (On Screen Display) generator 24, and the like are provided.

  The tuner 10 is a digital tuner for receiving digital broadcast signals such as terrestrial digital broadcast signals, BS digital broadcast signals, and CS digital broadcast signals. The tuner 10 is connected to the antenna 10a. For example, the tuner 10 detects a radio wave received by the antenna 10a according to a broadcast channel selected by the user via the operation unit 23, and acquires a broadcast signal from the obtained broadcast wave. Then, the acquired broadcast signal is sent to the AV selector 12.

  The tuner 10 may be an analog tuner for receiving analog broadcast signals such as UHF television broadcast signals, VHF television broadcast signals, BS analog broadcast signals, and CS analog broadcast signals.

  The external input unit 11 is connected to a video signal output unit and an audio signal output unit (not shown) of an external device via, for example, a cable, and acquires digital video signals and audio signals from the external device. The external input unit 11 sends digital video signals and audio signals acquired from an external device to the AV selector 12. Note that external devices include a recording / playback device, a game machine, and the like that record a video signal and an audio signal on a recording medium and reproduce the video signal and the audio signal recorded on the recording medium.

  The AV selector 12 selects one of a broadcast signal sent from the tuner 10 or a signal (video signal and audio signal) sent from the external input unit 11 and sends the selected signal to the separation unit 13.

  When the broadcast signal acquired by the tuner 10 is acquired from the AV selector 12, the separation unit 13 separates the broadcast signal into a video signal (RGB signal (R: red, G: green, B: blue)) and an audio signal, Each is sent to the video decoder 15 or the audio decoder 14. Further, when the separation unit 13 acquires the video signal and the audio signal input via the external input unit 11 from the AV selector 12, the separation unit 13 sends the acquired video signal and the audio signal to the video decoder 15 or the audio decoder 14, respectively. .

  The radio wave received by the antenna 10a includes EPG (program information indicating the genre, broadcast channel, broadcast start date / time, broadcast end date / time, etc. of the broadcast program broadcast by each broadcast station in addition to the radio wave related to the broadcast signal. Electronic program guide) Radio waves related to signals are periodically included. Therefore, when the broadcast signal acquired by the tuner 10 includes an EPG signal, the separation unit 13 separates the broadcast signal into a video signal, an audio signal, and an EPG signal, and each of them is a video decoder 15, an audio decoder 14, or an EPG decoder 16. To send.

  The audio decoder 14 performs a predetermined decoding / decompression process on the audio signal transmitted from the separation unit 13 and transmits the obtained audio signal to the audio processing unit 17. The audio processing unit 17 performs predetermined signal processing on the audio signal transmitted from the audio decoder 14 and then transmits the signal to the speaker 18. The speaker 18 outputs a sound based on the sound signal transmitted from the sound processing unit 17. Therefore, the speaker 18 outputs a sound based on a sound signal included in the broadcast signal acquired by the tuner 10 or a sound signal input via the external input unit 11.

  The audio processing unit 17 includes an A / D converter (analog / digital converter), a D / A converter (digital / analog converter), an amplifier (both not shown), and the like. The analog audio signal acquired from 14 is converted into a digital audio signal. The audio processing unit 17 performs predetermined signal processing on the digital audio signal, then converts the digital audio signal again to an analog audio signal by a D / A converter, and further converts the digital audio signal to a predetermined size by an amplifier as necessary. And then sent to the speaker 18.

  The video decoder 15 performs a predetermined decoding / decompression process on the video signal sent from the separation unit 13 and sends the obtained video signal to the video processor 19. Specifically, the video decoder 15 includes an A / D converter. When the input signal is analog, the video decoder 15 converts the analog video signal into a digital video signal and transmits the digital video signal to the video processor 19. The EPG decoder 16 performs a predetermined decoding / decompression process on the EPG signal sent from the separator 13 and sends the obtained EPG signal to the video processor 19.

  The video processor 19 includes a video processing unit 191, a histogram acquisition unit 192, a gamma correction unit 193, an output unit 194, and the like. The video signal sent from the video decoder 15 and the EPG signal sent from the EPG decoder 16 are included. Is input to the video processing unit 191 of the video processor 19.

  The video processing unit 191 performs, for example, IP (interlace / progressive) conversion processing, tint, color gain processing, edge enhancement on the video signal sent from the video decoder 15 or the EPG signal sent from the EPG decoder 16. Various signal processing such as processing and color matrix correction processing are executed.

  The video processing unit 191 performs IP conversion processing on the Y signal (luminance signal) and the C signal (color signal) of the video signal to suppress flickering of a still portion and reproduce a moving image with natural motion. A video signal that can be generated is generated. Further, the video processing unit 191 further performs color matrix correction processing and the like to generate a video signal that can reproduce a vivid color. In addition to the processing described above, the video processing unit 191 is configured to perform video adjustment, for example, adjustment processing of brightness, black level, color density, hue, enhancement (image enhancement), contrast, and the like. It may be.

  The video processing unit 191 converts the video signals (Y signal and C signal) obtained by executing various signal processes as described above into RGB video signals (RGB signals) and sends them to the gamma correction unit 193. At the same time, the Y signal is sent to the histogram acquisition unit 192.

  The gamma correction unit (correction means) 193 is a gamma based on a look-up table (hereinafter referred to as LUT) 22a input via the microcomputer 21 for the video signal (RGB signal) sent from the video processing unit 191. Execute correction processing. The LUT 22a indicates a gamma curve used for the gamma correction processing by the gamma correction unit 193. Specifically, for each color component (RGB) of the video signal (image signal), the gradation (input) before gamma correction is input. (Gradation) and the gradation after gamma correction (output gradation) are stored in association with each other.

  In accordance with the LUT 22a, the gamma correction unit 193 changes the input gradation (luminance) of each pixel for each color component of the video signal sent from the video processing unit 191 and outputs the output gradation (output luminance) corresponding to each input gradation. ) And the obtained video signal (output gradation) is sent to the output unit 194. The output unit (display control means) 194 sends the video signal sent from the gamma correction unit 193 to the liquid crystal module 20 according to a predetermined timing and causes the liquid crystal module 20 to display the video signal.

  The liquid crystal module 20 is a display device including a liquid crystal display, a plasma display, and the like, and displays an image based on an image signal sent from the video processor 19. For example, the liquid crystal module 20 displays a video based on a video signal included in a broadcast signal acquired by the tuner 10, a video based on a video signal input via the external input unit 11, and the like.

  The histogram acquisition unit 192 generates a histogram in the Y signal of the video signal based on the Y signal (luminance signal) sent from the video processing unit 191. The histogram is a gradation distribution indicating the number of pixels for each luminance (input gradation) value (Y signal value) in the pixels included in the video signal, and the histogram acquisition unit 192 generates a gradation distribution. Works as. The histogram acquisition unit 192 sends the generated histogram to the microcomputer 21.

  The microcomputer 21 includes a CPU (Central Processing Unit) that performs calculations, a ROM (Read Only Memory) that stores a control program indicating a control procedure of calculations performed by the CPU, and a RAM that stores temporary information associated with calculations performed by the CPU. (Random Access Memory). The microcomputer 21 reads the control program stored in advance in the ROM into the RAM and executes it, thereby controlling the operation of each part of the hardware included in the liquid crystal television 1 so that the entire apparatus functions as the image processing apparatus of the present invention. Let

  1 shows a configuration in which the microcomputer 21 is connected to the histogram acquisition unit 192, the gamma correction unit 193, the memory 22, the operation unit 23, and the OSD generator 24. However, the microcomputer 21 includes all other hardware units. It is connected. Each hardware unit described above operates in accordance with an instruction from the microcomputer 21.

  The memory (storage means) 22 is, for example, a flash memory, and stores in advance an LUT 22a used for gamma correction processing by the gamma correction unit 193, OSD screen data for OSD display of various menu screens on the liquid crystal television 1, and the like. Yes. When the microcomputer 21 reads the LUT 22a from the memory 22 and sends it to the gamma correction unit 193, the gamma correction unit 193 performs gamma correction processing using the LUT 22a on the video signal sent from the video processing unit 191. Can do.

The OSD generator 24 generates OSD screen data based on various information sent from the microcomputer 21, and sends the generated OSD screen data to the output unit 194 of the video processor 19.
The output unit 194 superimposes the OSD screen based on the OSD screen data transmitted from the OSD generator 24 on the video based on the video signal transmitted from the gamma correction unit 193 and transmits the superimposed image to the liquid crystal module 20. Thereby, an OSD screen showing various information can be displayed on the video displayed on the liquid crystal module 20.

  The OSD screen data is for displaying, for example, the operation status of the liquid crystal television 1, information to be notified to the user, and the like. In the present embodiment, the gamma adjustment screen for setting the gamma curve used for the gamma correction processing by the gamma correction unit 193 is also displayed as the OSD screen.

  The operation unit 23 includes various operation keys necessary for the user to operate the liquid crystal television 1, and when each operation key is operated by the user, a control signal corresponding to the operated operation key is sent to the microcomputer 21. To send. The microcomputer 21 executes an operation in accordance with an operation instruction from a user who operates the operation unit 23 by executing a corresponding control program by the CPU according to the control signal acquired from the operation unit 23.

  Although not shown, the liquid crystal television 1 of the present embodiment is configured to be remotely operable by a remote control device (hereinafter referred to as a remote controller). The liquid crystal television 1 and the remote controller communicate with each other by wireless communication in accordance with, for example, the home appliance association standard using infrared rays, the IEEE 802.11b standard, the Bluetooth standard, or the like. The liquid crystal television 1 includes a receiving unit (not shown) that receives a signal transmitted from the remote controller, and sends the signal received by the receiving unit to the microcomputer 21.

  The microcomputer 21 executes an operation according to an operation instruction from a user who operates the remote controller by executing a corresponding control program by the CPU in accordance with a signal sent from the receiving unit. In the following description, the remote controller is also included in the operation unit 23, and the operation from the user via the remote controller will be described as the operation of the operation unit 23. The operation unit 23 is provided with, for example, 1 to 12 numeric keys, cross keys (up / down / left / right keys), a determination key, a clear key, and the like.

  With the above-described configuration, the liquid crystal television 1 can output video and audio based on the broadcast signal acquired by the tuner 10 through the liquid crystal module 20 and the speaker 18, respectively. Further, the liquid crystal television 1 can output the video based on the video signal input from the external input unit 11 and the sound based on the audio signal by the liquid crystal module 20 and the speaker 18, respectively.

  Here, the liquid crystal television 1 of the present embodiment is configured such that the user can arbitrarily change a part of the LUT 22a (gamma curve) used for the gamma correction processing performed by the gamma correction unit 193. The gamma curve setting process will be described below.

  In the liquid crystal television 1, when the user selects the gamma setting mode for setting the gamma curve by operating the operation unit 23, the microcomputer 21 stores default OSD screen data (gamma adjustment) stored in the memory 22. Screen data). The microcomputer 21 sends the gamma adjustment screen data read from the memory 22 to the OSD generator 24. The OSD generator (display screen information generating means) 24 generates gamma adjustment screen data (display screen information) to be displayed on the liquid crystal module 20 based on the gamma adjustment screen data sent from the microcomputer 21, and the video processor 19. To the output unit 194.

  The output unit 194 superimposes the gamma adjustment screen (OSD screen) based on the gamma adjustment screen data sent from the OSD generator 24 on the video based on the video signal sent from the gamma correction unit 193 on the liquid crystal module 20. Display. Here, a gamma adjustment screen as shown in FIG. 2 is displayed.

  2 to 4 are schematic diagrams showing examples of the configuration of the gamma adjustment screen. In the gamma adjustment screen shown in FIG. 2, a menu including four items of new adjustment point addition, adjustment point movement, output gradation setting, and termination is displayed, and the user operates the up and down keys of the operation unit 23. Thus, any one of the four items can be selected. In addition, on the gamma adjustment screen, a histogram generated by the histogram acquisition unit 192 and a reference (default) gamma curve (optical gradation characteristics, gamma characteristics, correction characteristics) stored in advance in the memory 22 are displayed. The

  In the histogram in the gamma adjustment screen shown in FIG. 2, the horizontal axis represents the input gradation (luminance value), and the vertical axis represents the frequency (number of pixels). In addition, the gamma curve in the gamma adjustment screen shown in FIG. 2 shows the gradation (input gradation) of the image signal before the gamma correction processing is performed by the gamma correction unit 193 on the horizontal axis and the gamma correction on the vertical axis. The gradation (output gradation) of the image signal after the gamma correction processing by the unit 193 is shown.

  Here, in the liquid crystal television 1 of the present embodiment, the microcomputer (determining means) 21 allows the user to arbitrarily select a gamma adjustment screen based on the histogram generated by the histogram acquisition unit 192 when displaying the gamma adjustment screen on the liquid crystal module 20. Determine the range of gamma curves that can be changed. The range is determined with respect to the input gradation (luminance).

  Specifically, the microcomputer 21 is, for example, a range in which 80% of the total number of pixels included in the video signal is included around the average luminance of the luminance (gradation) of each pixel included in the video signal, or The range in which the standard deviation is a predetermined value is determined as a changeable range. The microcomputer 21 sends the minimum luminance and the maximum luminance indicating the determined range and the histogram generated by the histogram acquisition unit 192 to the OSD generator 24.

  Based on the gamma adjustment screen data acquired from the microcomputer 21, the minimum brightness and the maximum brightness, and the histogram, the OSD generator 24 has two broken lines indicating the minimum brightness and the maximum brightness, respectively, as shown in FIG. The gamma adjustment screen data in which the minimum point Pmin corresponding to the minimum luminance and the maximum point Pmax corresponding to the maximum luminance are added to the gamma curve is generated and sent to the output unit 194 of the video processor 19. Thereby, the gamma adjustment screen as shown in FIG. 2 can be displayed on the liquid crystal module 20.

  As described above, the liquid crystal television 1 according to the present embodiment automatically determines the range in which the gamma curve can be changed based on the histogram generated from the video signal. A curve change instruction may be given. Therefore, it is possible to save the operation of specifying the range in which the gamma curve is changed, and avoid unnecessary operations such as changing the gamma curve in a range that does not affect the video signal. In addition, as shown in FIG. 2, by indicating the range in which the gamma curve can be changed by two broken lines, the user can easily grasp in which range the gamma curve should be changed. Can be improved.

  2 is a range other than between the minimum point Pmin and the maximum point Pmax, that is, a range where the input gradation is smaller than the minimum point Pmin and a range where the input gradation is larger than the maximum point Pmax. The gamma curve cannot be changed. Thus, the gamma curve setting process can be performed efficiently without the user performing a gamma curve changing operation within an incorrect range. Further, by displaying the gamma curve and the histogram at the same time, it becomes easy to determine which part of the gamma curve should be changed in order to display the currently displayed image with higher image quality.

  When the user selects the “add new adjustment point” item on the gamma adjustment screen shown in FIG. 2, the microcomputer 21 adds a new adjustment point P1 in the vicinity of the minimum point Pmin of the gamma curve. When the user selects the “adjustment point movement” item in this state, the microcomputer 21 causes the liquid crystal module 20 to display a menu gamma adjustment screen as shown in FIG. 3 via the output unit 194.

  The menu of the gamma adjustment screen shown in FIG. 3 shows a state in which the “adjustment point movement” item is selected, and displays a procedure for moving the position of the adjustment point P1. Specifically, the right key indicates the currently selected adjustment point (the adjustment point P1 in FIG. 3 is one adjustment point P1) to the right (actually diagonally upward to the right). ) Key for moving in the direction, and the left key is for moving the currently selected adjustment point to the left (actually diagonally down to the left) as indicated by the white arrow. Is shown.

  The upper key is used to select an adjustment point with an input gradation higher than the currently selected adjustment point, and the lower key is used to adjust an input gradation lower than the currently selected adjustment point. This is a key for selecting a point. The enter key is a key for ending the operation of moving the position of such an adjustment point.

  That is, when the user operates the right key on the gamma adjustment screen shown in FIG. 3, the microcomputer 21 moves the adjustment point P1 along the gamma curve to a position (point) where the input gradation is a high gradation by a predetermined amount. . When the user operates the left key, the microcomputer 21 moves the adjustment point P1 along the gamma curve to a position (point) where the input gradation is a low gradation by a predetermined amount. In addition, when the user operates the up key or the down key, the microcomputer 21 appropriately changes the adjustment point that is the target of the process of moving the position.

  When the user selects the “output gradation setting” item on the gamma adjustment screen shown in FIG. 2 or when the user operates the enter key on the gamma adjustment screen shown in FIG. When the “output gradation setting” item is selected later, the microcomputer 21 causes the liquid crystal module 20 to display a menu gamma adjustment screen as shown in FIG. 4 via the output unit 194.

  The menu of the gamma adjustment screen shown in FIG. 4 shows a state in which the “output gradation setting” item is selected, and displays a procedure for changing (setting) the output gradation at the adjustment point P1. Specifically, the up key indicates the output gradation at the currently selected adjustment point (the adjustment point P1 in FIG. 4 is one adjustment point P1) in the upward direction (high order) as indicated by a white arrow. Key is a key for changing the output gradation at the currently selected adjustment point downward (low gradation) as indicated by a white arrow. It is shown that.

  The right key is used to select an adjustment point with an input tone higher than the currently selected adjustment point, and the left key is used to adjust an input tone lower than the currently selected adjustment point. This is a key for selecting a point. Further, the determination key is a key for ending the operation for changing the output gradation for each adjustment point.

That is, when the user operates the up key on the gamma adjustment screen shown in FIG. 4, the microcomputer 21 moves the output gradation of the adjustment point P1 by a predetermined amount to the high gradation side. When the user operates the down key, the microcomputer 21 moves the output gradation of the adjustment point P1 by a predetermined amount to the low gradation side. Further, the microcomputer 21 interpolates the gamma curve between the minimum point Pmin and the maximum point Pmax as the adjustment point P1 moves. When interpolating a gamma curve, a gamma curve that passes through the minimum point Pmin, the maximum point Pmax, and the adjustment point P1 may be generated according to, for example, a Bezier curve or a spline curve.
In addition, when the user operates the right key or the left key, the microcomputer 21 appropriately changes the adjustment point to be processed for changing the output gradation.

  FIG. 5 is a schematic diagram showing an example of a gamma curve changed via the gamma adjustment screen. FIG. 5A shows a gamma curve when the output gradation is changed to a high gradation by an amount indicated by a white arrow with respect to one adjustment point P1. FIG. 5B shows a gamma curve when the output gradation is changed to a high gradation by the amount indicated by the white arrow for each of the two adjustment points P1 and P2. FIG. 5C shows a gamma curve when the output gradation is changed to a low gradation by the amount indicated by the white arrow with respect to one adjustment point P1.

  As described above, each time the position of each adjustment point (the adjustment point P1 in FIGS. 2 to 4) is changed, the microcomputer 21 accepts the change of the position of each adjustment point, and on the gamma curve in the gamma adjustment screen. Change the position of the adjustment point. Further, as described above, the microcomputer (accepting means) 21 receives the change of the output gradation at each adjustment point and changes the gamma curve in the gamma adjustment screen every time the output gradation at each adjustment point is changed. . Note that when the gamma curve is changed, the microcomputer 21 newly generates an LUT 22 a based on the changed gamma curve and stores the LUT 22 a in the memory 22.

  Further, the microcomputer 21 sends out a new LUT 22a stored in the memory 22 to the gamma correction unit 193, and causes the gamma correction unit 193 to execute a gamma correction process based on the LUT 22a, so that an image based on the processed video signal is displayed. It is displayed on the liquid crystal module 20. At this time, the gamma adjustment screen remains displayed on the video as the OSD screen.

  In the gamma adjustment screen shown in FIG. 2, when the user selects the “end” item, the “end” item is displayed after the user operates the enter key on the gamma adjustment screen shown in FIG. If the user selects the “End” item after the user has operated the enter key on the gamma adjustment screen shown in FIG. The display of the gamma adjustment screen shown in FIG. Specifically, the microcomputer 21 terminates the OSD screen data generation instruction for displaying the gamma adjustment screen to the OSD generator 24.

  As described above, in the liquid crystal television 1 of the present embodiment, the user can arbitrarily change a part of the gamma curve, so that it is possible to execute a gamma correction process that can realize the user's favorite image quality. Further, the range of the gamma curve that can be arbitrarily changed by the user is automatically determined based on the histogram of the Y signal (luminance) of the video signal, and in which range the gamma curve is to be changed. In addition to saving time and effort, it is possible to avoid unnecessary operations such as changing the gamma curve within a range that does not affect the video signal, and to improve operability.

  Further, as shown in FIGS. 2 to 4, by simultaneously displaying the histogram of the Y signal of the video signal and the gamma curve, it is easy to grasp the relationship between them, and the change of the gamma curve is set based on the histogram. Therefore, an appropriate setting process can be performed. In addition, each time a change of the gamma curve is set via the gamma adjustment screen, the LUT 22a is updated, and a gamma correction process based on the updated LUT 22a is performed on the currently displayed video, thereby allowing the user to The effect of the gamma correction process using the changed gamma curve can be confirmed sequentially.

  The LUT 22a may be updated whenever the gamma curve is changed, or may be registered in the memory 22 for each user, for example. Further, the LUT 22a may be prepared for each genre of video signals such as news, movies, and sports.

  As described above, in the liquid crystal television 1 of the present embodiment, the gamma correction unit 193 can increase the processing speed by performing the gamma correction processing using the LUT 22a. However, the present invention is not limited to such a configuration, and a configuration in which a function indicating a changed gamma curve is calculated via a gamma adjustment screen and a gamma correction process according to this function may be performed. That is, the gamma correction unit 193 calculates an output gradation (luminance) by substituting each input gradation (luminance) of the video signal input from the video processing unit 191 into the calculated function. The output gradations may be sent to the output unit 194.

  FIG. 6 is a schematic diagram showing an example of a gamma curve and a histogram displayed on the gamma adjustment screen. FIG. 6A shows a gamma curve and histogram similar to the gamma curve and histogram in the gamma adjustment screen shown in FIGS. 2 to 4, and FIG. 6B shows the gamma curve and histogram shown in FIG. The enlarged view of the gamma curve and histogram shown in FIG. As shown in the histogram in FIG. 6A, when the Y signal of the video signal is concentrated on the intermediate gradation, the range from the minimum point Pmin to the maximum point Pmax may be enlarged and displayed.

  By adopting such a configuration, the gamma curve in a changeable range can be enlarged and displayed so that it is easy to see. For example, when setting the position of the adjustment point in detail, the output gradation at each adjustment point is set in detail It is effective in the case. Even when the Y signal of the video signal is concentrated on the gradation within the predetermined range, the predetermined range may be enlarged and displayed in the same manner.

  Hereinafter, a process for setting (changing) a gamma curve (specifically, LUT 22a) used for the gamma correction process performed by the gamma correction unit 193 in the liquid crystal television 1 of the present embodiment will be described with reference to a flowchart. 7 to 9 are flowcharts showing the procedure of the gamma curve setting process by the liquid crystal television 1. Note that the processing procedure shown below is an example, and the present invention is not limited to this. The following processing is executed by the CPU of the microcomputer 21 in accordance with a control program stored in advance in the ROM of the microcomputer 21.

  When the user of the liquid crystal television 1 wants to change the gamma curve while viewing the image being displayed on the liquid crystal module 20, he / she operates the operation unit 23 to select a gamma setting mode for setting the gamma curve. The microcomputer 21 determines whether or not the gamma setting mode has been selected (S1). If it is determined that the gamma setting mode has not been selected (S1: NO), the microcomputer 21 stands by.

  If the microcomputer 21 determines that the gamma setting mode has been selected (S1: YES), the microcomputer 21 determines a gamma curve range (changeable range) that can be arbitrarily changed by the user based on the histogram generated by the histogram acquisition unit 192. Determine (S2). The histogram acquisition unit 192 generates a histogram every time a Y signal is sent from the video processing unit 191.

  The microcomputer 21 reads the default OSD screen data (gamma adjustment screen data) from the memory 22, the read gamma adjustment screen data, the histogram acquired from the histogram acquisition unit 192, and the minimum brightness indicating the changeable range determined by itself. And the maximum luminance are sent to the OSD generator 24. Therefore, the microcomputer 21 uses the OSD generator 24 to generate gamma adjustment screen data to which the histogram, the minimum point Pmin, and the maximum point Pmax are added (S3).

  The microcomputer 21 superimposes the gamma adjustment screen based on the gamma adjustment screen data on the image displayed on the liquid crystal module 20 by sending the generated gamma adjustment screen data to the output unit 194 of the video processor 19. Are displayed (S4). Here, the gamma adjustment screen shown in FIG. 2 is displayed on the liquid crystal module 20.

  In the gamma adjustment screen shown in FIG. 2, the microcomputer 21 determines whether or not the user has selected the “add new adjustment point” item (S5), and if it is determined that the user has selected (S5: YES), the gamma A new adjustment point P1 is added and displayed near the minimum point Pmin of the gamma curve in the adjustment screen (S6). Specifically, the microcomputer 21 generates gamma adjustment screen data in which the new adjustment point P1 is added in the vicinity of the minimum point Pmin and sends it to the output unit 194 of the video processor 19, and the gamma adjustment based on this gamma adjustment screen data. An adjustment screen is displayed on the liquid crystal module 20. If the microcomputer 21 determines that the user has not selected the “add new adjustment point” item (S5: NO), it skips the process of step S6.

  In the gamma adjustment screen shown in FIG. 2, the microcomputer 21 determines whether the user has selected the “adjustment point movement” item (S7), and if it has determined that the user has not selected (S7: NO), The process proceeds to step S13. If the microcomputer 21 determines that it has been selected (S7: YES), it displays a menu as shown in FIG. 3, and determines whether or not the user has accepted the movement of the adjustment point by operating the left and right keys (S8). ). If it is determined that the movement has been accepted (S8: YES), the microcomputer 21 moves the currently selected adjustment point according to the accepted movement (S9).

  Specifically, when the user operates the left key (or the right key), the microcomputer 21 sets the currently selected adjustment point at the position where the input gradation is low (or high) along the gamma curve. The gamma adjustment screen data moved to is generated and sent to the output unit 194 of the video processor 19, and the gamma adjustment screen based on the gamma adjustment screen data is displayed on the liquid crystal module 20.

  If it is determined that the movement of the adjustment point has not been accepted (S8: NO), the microcomputer 21 skips the process of step S9 and determines whether or not the user has accepted selection of the adjustment point by operating the up / down key. (S10). If it is determined that selection of an adjustment point has been accepted (S10: YES), the microcomputer 21 changes the adjustment point to be processed (S11), and returns the process to step S8.

  Specifically, when the user operates the up key (or down key), the microcomputer 21 processes an adjustment point whose input gradation is higher (or lower gradation) than the currently selected adjustment point. To change. Then, the microcomputer 21 generates gamma adjustment screen data with this adjustment point as a processing target, sends it to the output unit 194 of the video processor 19, and causes the liquid crystal module 20 to display a gamma adjustment screen based on this gamma adjustment screen data. .

  If it is determined that selection of an adjustment point has not been accepted (S10: NO), the microcomputer 21 determines whether or not the user has accepted the end of the process of moving the position of the adjustment point by operating the enter key ( S12). If it is determined that the end is not accepted (S12: NO), the microcomputer 21 returns the process to step S8.

  When it is determined that the end is accepted (S12: YES), or when it is determined that the user does not select the “adjustment point movement” item on the gamma adjustment screen shown in FIG. 2 (S7: NO), the microcomputer 21 It is determined whether or not the user has selected the “output gradation setting” item on the gamma adjustment screen (S13). If it is determined that no selection has been made (S13: NO), the microcomputer 21 proceeds to step S22.

  If the microcomputer 21 determines that it has been selected (S13: YES), it displays a menu as shown in FIG. 4 and determines whether or not the user has accepted the change of the output gradation at the adjustment point by operating the up and down keys. Judgment is made (S14). If it is determined that the change of the output gradation has been received (S14: YES), the microcomputer 21 changes the output gradation for the currently selected adjustment point and changes the gamma curve in the gamma adjustment screen to display it. (S15).

  Specifically, when the user operates the up key (or down key), the microcomputer 21 outputs a predetermined amount of output gradation corresponding to the currently selected adjustment point at a high gradation (or low gradation) position. The gamma curve is changed (interpolated) along with this movement. Then, the microcomputer 21 generates gamma adjustment screen data displaying the changed gamma curve and sends it to the output unit 194 of the video processor 19 to display the gamma adjustment screen based on this gamma adjustment screen data on the liquid crystal module 20. .

  The microcomputer 21 newly generates an LUT 22a based on the gamma curve changed in step S15 and stores it in the memory 22 (S16). The microcomputer 21 causes the gamma correction unit 193 to execute the gamma correction process based on the new LUT 22a stored in the memory 22 (S17), and the video signal sent from the video processing unit 191 to the gamma correction unit 193 is new. A gamma correction process based on the LUT 22a is performed, and an image based on the obtained image signal is displayed on the liquid crystal module 20 via the output unit 194 (S18).

  After displaying the video based on the video signal that has been subjected to the gamma correction processing based on the new LUT 22a, or when determining that the change of the output tone of the adjustment point has not been accepted (S14: NO), the microcomputer 21 In the gamma adjustment screen shown in FIG. 6, it is determined whether or not the user has accepted selection of an adjustment point by operating the left and right keys (S19). When it is determined that the selection of the adjustment point has been received (S19: YES), the microcomputer 21 changes the adjustment point to be processed for changing the output gradation (S20), and returns the process to step S14.

  Specifically, when the user operates the left key (or the right key), the microcomputer 21 processes an adjustment point whose input gradation is lower (or higher) than the currently selected adjustment point. To change. Then, the microcomputer 21 generates gamma adjustment screen data with this adjustment point as a processing target, sends it to the output unit 194 of the video processor 19, and causes the liquid crystal module 20 to display a gamma adjustment screen based on this gamma adjustment screen data. .

  If it is determined that the selection of the adjustment point has not been accepted (S19: NO), the microcomputer 21 determines whether or not the user has accepted the end of the process of changing the output gradation at the adjustment point by operating the enter key. (S21). If it is determined that the end has not been accepted (S21: NO), the microcomputer 21 returns the process to step S14.

  If it is determined that the end has been accepted (S21: YES), or if it is determined that the user has not selected the “output gradation setting” item on the gamma adjustment screen shown in FIG. 2 (S13: NO), the microcomputer 21 In the gamma adjustment screen shown in FIG. 2, it is determined whether or not the user has selected the “end” item (S22). If the microcomputer 21 determines that it has not been selected (S22: NO), it proceeds to step S5 and repeats the above-described steps S5 to S22. If the microcomputer 21 determines that it has been selected (S22: YES), it ends the display of the gamma adjustment screen and ends the above-described gamma curve setting process.

  In the above-described embodiment, as illustrated in FIGS. 2 to 5, the example in which one or two adjustment points are set via the gamma adjustment screen has been described. The number of adjustment points that can be made is not limited to these. Further, as shown in FIG. 5B, when a plurality of adjustment points are set, each adjustment point may be displayed in a different color, or only the currently selected adjustment point is changed to another adjustment point. You may make it display with the color different from a point. With this configuration, when the user performs an operation such as selecting an adjustment point, moving the adjustment point, or changing an output gradation with respect to the adjustment point, the adjustment point to be processed can be easily identified.

  In the above-described embodiment, as illustrated in FIGS. 2 to 4, the example in which the gamma curve and the histogram are displayed on the gamma adjustment screen has been described. However, for example, only the gamma curve to which the minimum point Pmin and the maximum point Pmax are added may be displayed as an OSD screen on the video without displaying the histogram. Even in such a configuration, the range of the gamma curve that can be arbitrarily changed by the user is automatically determined, so that it is possible to save time and effort to determine in which range the gamma curve should be changed and to influence the video signal. It is possible to avoid useless operations such as changing the gamma curve within a range that is not given.

  In the embodiment described above, the configuration in which the gamma adjustment screen is displayed as an OSD screen superimposed on the image being displayed on the liquid crystal module 20 has been described as an example. However, the present invention is not limited to this configuration, and only the gamma adjustment screen may be displayed on the entire liquid crystal module 20.

It is a block diagram which shows the structural example of the liquid crystal television which concerns on this embodiment. It is a schematic diagram which shows the structural example of a gamma adjustment screen. It is a schematic diagram which shows the structural example of a gamma adjustment screen. It is a schematic diagram which shows the structural example of a gamma adjustment screen. It is a schematic diagram which shows the example of the gamma curve changed via the gamma adjustment screen. It is a schematic diagram which shows the example of the gamma curve and histogram which are displayed on a gamma adjustment screen. It is a flowchart which shows the procedure of the gamma curve setting process by a liquid crystal television. It is a flowchart which shows the procedure of the gamma curve setting process by a liquid crystal television. It is a flowchart which shows the procedure of the gamma curve setting process by a liquid crystal television.

Explanation of symbols

1 LCD TV (image processing device)
19 Video processor 192 Histogram acquisition unit (generation means)
193 Gamma correction unit (correction means)
194 Output unit (display control means)
21 Microcomputer (deciding means, receiving means)
22 Memory (storage means)
24 OSD generator (display screen information generating means)

Claims (6)

Correction means for correcting the input gradation of the input image signal to an output gradation corresponding to the input gradation and outputting it, and display control for displaying on the display device an image based on the image signal output by the correction means An image processing apparatus comprising:
Generating means for generating a gradation distribution indicating the number of pixels for each input gradation of the pixels included in the image signal;
A determination unit that determines a range of input gradations in which a corresponding output gradation can be changed based on the gradation distribution generated by the generation unit;
Display screen information generating means for generating display screen information for displaying the gradation distribution generated by the generating means and the correction characteristics indicating the relationship between the input gradation and the output gradation in the correction processing performed by the correcting means;
A receiving means for receiving a change of the output gradation to the extent that the determining means has determined,
An adding means for adding a change indicating the change accepted by the accepting means to a correction characteristic in the display screen based on the display screen information generated by the display screen information generating means ,
The display control means causes the display device to display the display screen to which the addition means has added the change point,
When the accepting unit accepts a plurality of changes, the adding unit is configured to add a change point indicating each change accepted by the accepting unit in different colors,
The correction means is configured to correct the input gradation of the image signal to an output gradation corresponding to the input gradation based on the output gradation received by the receiving means. A featured image processing apparatus.   The image processing according to claim 1, wherein the determination unit is configured to determine a range including pixels having a predetermined number of pixels with respect to the total number of pixels included in the image signal. apparatus. The display control means is configured to display a display screen based on the display screen information generated by the display screen information generation means on the display device so as to be superimposed on an image based on the image signal. The image processing apparatus according to claim 1 or 2 . The display screen information generating unit, any one of the things to claims 1-3, characterized in that is arranged to enlarge the gradation distribution and the correction characteristic in the range of the determining means has determined An image processing apparatus according to 1. A means for generating a lookup table in which the input gradation and the output gradation in the correction processing performed by the correction means are associated with each other based on the output gradation received by the reception means;
Storage means for storing the generated lookup table,
Said correction means, based on a lookup table stored in the storage means, any of the preceding claims, characterized to 4 that is arranged to correct the input gray level of the image signal The image processing apparatus according to one. In an image processing method for correcting an input gradation of an input image signal to an output gradation corresponding to the input gradation and displaying an image based on the corrected image signal on a display device,
Generating a gradation distribution indicating the number of pixels for each input gradation of the pixels included in the image signal;
A step of determining a range of input gradations in which a corresponding output gradation can be changed based on the generated gradation distribution;
Generating display screen information for displaying the generated gradation distribution and correction characteristics indicating a relationship between an input gradation and an output gradation in a correction process performed on the image signal;
Receiving the change of the output gradation within the determined range;
An additional step of adding a change indicating the received change to a correction characteristic in the display screen based on the generated display screen information;
Displaying the display screen with the change added on the display device;
Correcting the input gradation of the image signal to an output gradation corresponding to the input gradation based on the output gradation received the change ,
In the image processing method , the adding step adds a change point indicating each received change in a different color when a plurality of changes are received .

Images