Signal processing device, signal processing method, and computer program

Abstract

To provide a signal processing device capable of adjusting knee correction parameters without allowing a user to consider a dynamic range of an input signal or an output signal level.SOLUTION: A signal processing device includes: holding means of holding data of a tone curve to be applied to an input image; correction parameter acquisition means of acquiring a high luminance side gradation correction parameter for adjusting a correction amount of high luminance side gradation correction of the tone curve; correction amount calculation means of calculating the correction amount of the high luminance side gradation correction based on a maximum output level of the tone curve and the high luminance side gradation correction parameter so as to maintain a dynamic range of the tone curve; correction curve generation means of generating a correction curve by applying the high luminance side gradation correction to the tone curve; and correction curve application means of applying the correction curve to the input image.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a signal processing device, a signal processing method, a computer program, and the like. [Background technology]

[0002] Knee correction is generally used as a means of correcting the high-brightness gradation of an image. Knee correction is a process that suppresses the output level by changing the slope (knee slope) of the high-brightness area above a specified output level (knee point). Users can adjust the image by changing the position of the knee point and the degree of the knee slope.

[0003] Knee compensation may also be used when you want to keep the output signal level within a specified level, such as 100%. By performing knee compensation, you can compress only the high-brightness parts of the image signal and keep it within a specified level without affecting the intermediate brightness or lower.

[0004] However, if the knee point position and knee slope are not set appropriately, the dynamic range of the input signal may be unintentionally reduced or may fall below the target output signal level. In such cases, the dynamic range of the input signal may not be fully utilized, the signal level may be unintentionally clipped on the display device side, and color distortion may occur on the high-brightness side.

[0005] To suppress the unintended effects of tone correction settings on output signals, for example, in Patent Document 1, tone correction is performed based on control points and histograms set by the user. In Patent Document 2, a representative luminance value in a specific range contained in an image is calculated, and a target representative value and target dynamic range are set for that. From these set values, target bright luminance values ​​and target dark luminance values ​​are calculated and brightness conversion is performed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-076908 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-254415 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the above-mentioned conventional technologies have the following problems when performing gradation correction on the high-brightness side. In Patent Document 1, correction is applied to the entire curve, not just the high-brightness side. In addition, a histogram must be generated, and the user must set parameters based on the histogram, so the amount of correction applied varies depending on the input signal. In Patent Document 2, the user sets only the target representative luminance value and target dynamic range, and cannot specify the knee point. In addition, a calculation means is required to calculate the representative luminance value, and the representative luminance value varies depending on the input signal.

[0008] The present invention has been made in consideration of the above problems, and has as its object to provide a signal processing device that is capable of adjusting the parameters of knee correction without requiring the user to take into account the dynamic range of the input signal or the output signal level. [Means for solving the problem]

[0009] A signal processing device according to one aspect of the present invention includes: a storage means for storing data of a tone curve to be applied to an input image; a correction parameter acquisition means for acquiring a high-luminance side gradation correction parameter for adjusting the amount of high-luminance side gradation correction of the tone curve; a correction amount calculation means for calculating the correction amount of the high-luminance side gradation correction based on the maximum output level of the tone curve and the high-luminance side gradation correction parameter so as to maintain the dynamic range of the tone curve; a correction curve generating means for generating a correction curve by applying the high-luminance side gradation correction to the tone curve; a correction curve applying means for applying the correction curve to the input image; The present invention is characterized by having the following. [Effects of the Invention]

[0010] According to the present invention, it is possible to realize a signal processing device that is capable of adjusting the parameters of knee correction without requiring the user to take into consideration the dynamic range of the input signal or the output signal level. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a functional block diagram showing an example of the internal configuration of an imaging device according to a first embodiment. [Figure 2] 2 is a functional block diagram showing an example of the configuration of a knee correction processing unit 200 in an image processing unit 112 according to the first embodiment. FIG. [Figure 3] 5 is a flowchart showing an example of processing by a knee correction processing unit 200 in the signal processing method according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of a method for setting a knee point according to the first embodiment. [Figure 5] FIG. 4 is a diagram illustrating an example of a method for generating a knee slope according to the first embodiment. [Figure 6] 5A to 5C are diagrams illustrating an example of a method for a user to set a knee point and a knee slope according to the first embodiment. [Figure 7] FIG. 10 is a diagram showing an example of a message notifying that the knee slope according to the first embodiment is set according to the maximum output level. [Figure 8] 10 is a flowchart showing an example of processing in a signal processing method according to the second embodiment. [Figure 9] FIG. 10 is a diagram illustrating an example of a method for setting a knee slope according to the second embodiment. [Figure 10] FIG. 10 is a diagram showing an example of a message notifying that the knee point value according to the second embodiment is set in accordance with the maximum output level. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments. In each drawing, the same members or elements are designated by the same reference numerals, and duplicate descriptions will be omitted or simplified.

[0013] <Embodiment 1> Fig. 1 is a functional block diagram showing an example of the internal configuration of an imaging device according to embodiment 1. Note that some of the functional blocks shown in Fig. 1 are realized by causing a CPU or the like serving as a computer (not shown) included in the imaging device to execute a computer program stored in a memory serving as a storage medium (not shown).

[0014] However, some or all of these functions may be implemented by hardware, which may be a dedicated circuit (ASIC) or a processor (reconfigurable processor, DSP).

[0015] 1 may not be contained in the same housing, but may be configured as separate devices connected to each other via signal paths. The above description regarding FIG. 1 also applies to FIG. 2.

[0016] Although the imaging device according to this embodiment functions as a signal processing device, the signal processing device may be configured separately from the imaging device, and the signal processing method according to this embodiment may be performed by an external device such as a PC connected to the imaging device.

[0017] The imaging device 100 includes an imaging lens 101, an aperture 102, an ND filter 103, an imaging element 110, an A / D converter 111, an image processing unit 112, a memory control unit 113, and a system control unit 120. The imaging device 100 further includes a nonvolatile memory 121, a system memory 122, a system timer 123, a memory 130, a power supply control unit 140, a power supply unit 170, and an I / F 180.

[0018] The imaging lens 101 is a lens group including a zoom lens, a focus lens, and a shift lens, and forms an image of a subject. The aperture 102 is an aperture used to adjust the amount of light. The ND filter 103 is a neutral density filter.

[0019] The image sensor 110 is, for example, a CMOS image sensor, and also has functions such as controlling accumulation by an electronic shutter, changing gain, changing readout speed, etc. The A / D converter 111 is used to convert the analog signal output from the image sensor 110 into a digital signal.

[0020] The image processing unit 112 performs image processing on image data from the A / D converter 111 or the memory control unit 113. The image processing includes, for example, predetermined pixel interpolation processing, resizing processing such as reduction processing, image rotation and geometric deformation, image clipping, detection processing of brightness information, color information, characteristic subjects, etc., color conversion processing, gamma correction processing, digital gain addition processing, etc.

[0021] The gamma correction process includes knee correction, which corrects high-luminance gradations by changing the position of the knee point and the knee slope (a value representing the slope of the knee curve (knee line)). The image processing in the image processing unit 112 includes image processing using a dedicated arithmetic circuit and image processing using a 3D-LUT processing circuit. The image processing unit 112 also performs predetermined arithmetic processing using image data from the image sensor 110 and transmits the arithmetic results to the system control unit 120.

[0022] Based on the transmitted calculation results, the system control unit 120 performs exposure control, distance measurement control, white balance control, etc. This allows for TTL (through-the-lens) AF (autofocus) processing, AE (auto exposure) processing, AWB (auto white balance) processing, etc.

[0023] The output data from the A / D converter 111 is written to the memory 130 via the image processing unit 112 and the memory control unit 113, or via the memory control unit 113. The memory 130 stores the image data from the imaging element 110 or the image processing unit 112.

[0024] The memory 130 can also be used to temporarily store images that have been processed by the image processing unit 112, and then return the images to the image processing unit 112 for further image processing. The memory 130 has a storage capacity sufficient to store moving images and audio for a predetermined period of time.

[0025] The nonvolatile memory 121 is an electrically erasable and recordable memory, such as an EEPROM. The nonvolatile memory 121 stores constants, programs, etc. for the operation of the system control unit 120. The programs referred to here refer to computer programs for executing various flowcharts, which will be described later.

[0026] The system control unit 120 functions as a control unit for controlling the imaging device 100. The system control unit 120 includes a CPU serving as a computer (not shown), and executes the computer programs recorded in the nonvolatile memory 121 described above to perform each process of this embodiment, which will be described later.

[0027] The system memory 122 uses RAM and stores constants and variables for the operation of the system control unit 120, programs read from the nonvolatile memory 121, etc. The system timer 123 is a timing unit that measures the time used for various controls and the time of a built-in clock.

[0028] The power supply control unit 140 is composed of a battery detection circuit, a DC-DC converter, a switch circuit for switching between powered blocks, etc., and detects whether a battery is installed, the type of battery, and the remaining battery power. Based on the detection results and instructions from the system control unit 120, the power supply control unit 140 controls the DC-DC converter to supply the required voltage for the required period to each unit, including the external recording medium 150.

[0029] The power supply unit 170 is made up of primary batteries such as alkaline batteries or lithium batteries, secondary batteries such as NiCd batteries, NiMH batteries, or Li-ion batteries, an AC adapter, etc. The I / F 180 is an interface with an external recording medium 150 such as a memory card or hard disk, and an external display device 160. The external recording medium 150 is a recording medium such as a memory card for recording captured images and exchanging data with the outside, and may be a semiconductor memory or the like.

[0030] 2 is a functional block diagram showing an example of the configuration of a knee correction processing unit 200 in the image processing unit 112 according to the first embodiment. In the first embodiment, the knee correction processing unit 200 allows the user to adjust the knee correction parameters without having to consider the dynamic range of the input signal or the output signal level. Note that the knee correction in this embodiment is intended to perform high-luminance gradation correction of the input signal.

[0031] The knee correction processing unit 200 includes a knee correction parameter acquisition unit 202, a knee correction amount calculation unit 203, a RAM 204, a correction curve generation unit 205, a correction curve application necessity acquisition unit 206, and a correction curve application unit 207. An input image 201 is an image based on an output signal from the A / D converter 111, and the knee correction processing unit 200 applies knee correction to the input image 201 and outputs an output image 208.

[0032] First, the knee correction processing unit 200 acquires the maximum output level and knee point specified by the user via the knee correction parameter acquisition unit 202. Then, based on these, the knee correction amount calculation unit 203 calculates the knee slope (a value representing the gradient of the knee curve (knee line)).

[0033] The knee correction parameter acquisition unit 202 functions as a correction parameter acquisition unit that acquires a high-luminance side gradation correction parameter for adjusting the amount of high-luminance side gradation correction of the tone curve. In this embodiment, the high-luminance side gradation correction parameter is a parameter for knee correction applied to the tone curve, and is either a parameter for the knee point or knee slope at which knee correction starts.

[0034] Furthermore, the knee correction amount calculation unit 203 functions as a correction amount calculation unit that calculates the amount of high-luminance-side gradation correction so as to maintain the dynamic range of the tone curve, based on the maximum output level of the tone curve and the high-luminance-side gradation correction parameters. That is, the knee correction amount calculation unit 203 calculates the amount of knee correction so as to maintain the dynamic range of the tone curve, based on the maximum output level and the knee correction parameters.

[0035] The RAM 204 stores tone curve data and functions as a storage means for storing data of the tone curve to be applied to the input image. The correction curve generation unit 205 generates a correction curve by applying knee correction to the tone curve data read from the RAM 204. The correction curve generation unit 205 also functions as a correction curve generation means for generating a correction curve by applying high-luminance-side gradation correction to the tone curve.

[0036] The correction curve application unit 207 applies a correction curve in accordance with the result acquired from the correction curve application necessity acquisition unit 206, and outputs an output image 208. Here, the correction curve application unit 207 functions as a correction curve application means that applies a correction curve to an input image.

[0037] 3 is a flowchart showing an example of processing by the knee correction processing unit 200 in the signal processing method according to the first embodiment, and shows an example of the processing method of the knee correction processing unit 200. Note that the operation of each step in the flowchart of FIG. 3 is performed sequentially by a CPU or the like serving as a computer in the system control unit 120 executing a computer program stored in memory.

[0038] In step S301, the knee correction processing unit 200 acquires tone curve data from the system control unit 120 and loads it into the RAM 204.

[0039] In step S302, the correction curve application necessity acquisition unit 206 determines whether or not to apply automatic knee slope calculation based on an instruction from the user. That is, it determines whether or not an instruction to apply automatic knee slope calculation has been given from the user. If the determination is Yes, the process proceeds to step S303. If the determination is No, the process proceeds to step S307.

[0040] Here, step S302 functions as a determination step (determination means) that receives and determines whether or not to apply high-luminance-side gradation correction of the correction amount calculated by the knee-correction-amount calculation unit 203 serving as correction amount calculation means. Also, if the determination step (determination means) determines that high-luminance-side gradation correction is to be applied, the process proceeds to step S303 and subsequent steps, whereby the correction curve is applied to the input image.

[0041] That is, in step S303, the knee correction parameter acquisition unit 202 acquires the knee point and the output level, that is, receives input of the maximum output level and the knee point of the knee correction from the user.

[0042] Here, steps S301 and S303 function as correction parameter acquisition steps for acquiring high-luminance side tone correction parameters for adjusting the maximum output level of the tone curve applied to the input image and the high-luminance side tone correction level of the tone curve.

[0043] FIG. 4 is a diagram showing an example of a method for setting a knee point according to the first embodiment, and shows an example of a GUI (Graphical User Interface) for setting knee correction, which is acquired by the knee correction parameter acquisition unit 202.

[0044] The GUI screen 406 in FIG. 4 has a section 401 for accepting on / off of automatic knee slope calculation, a section 402 for accepting output level (maximum output level of knee correction), a section 403 for accepting knee point, and a section 404 for accepting knee slope.

[0045] 4, the section 401 that accepts the on / off setting of the automatic knee slope calculation is set to on, and as a result, it is determined in step S302 that the automatic knee slope calculation is to be applied. As a result of the determination that the automatic knee slope calculation is to be applied, the section 404 that accepts the knee slope is displayed so as not to accept input from the user. That is, if it is determined in step S302 that automatic calculation of the knee slope as the knee correction amount is to be applied, the knee slope parameter input by the user is not accepted.

[0046] In the example of Fig. 4, when the user places the cursor on the section 403 that accepts the knee point, a setting screen 405 for setting the knee point is displayed, and the user can specify the knee point as an adjustment parameter. In Fig. 4, when the cursor is placed on each of the sections 401 to 404, a setting screen 405 for setting the corresponding setting parameter is displayed on the right side of the screen.

[0047] 4, the user can set the output level (maximum output level of knee correction) and knee point, and the settings are acquired in step S303. In step S304, knee correction amount calculation unit 203 calculates a knee slope (a value indicating the slope of the knee curve) from the maximum output level and knee point received from the user.

[0048] Here, step S304 functions as a correction amount calculation step for calculating the amount of high-luminance side gradation correction based on the maximum output level and the high-luminance side gradation correction parameter so as to maintain the dynamic range of the tone curve.

[0049] Fig. 5 is a diagram showing an example of a knee slope generation method according to the first embodiment, with the vertical axis representing the output signal level and the horizontal axis representing the input signal level. In Fig. 5, a knee slope ks1 of knee curve 1 is generated for a tone curve 501 based on a maximum output level ymax and a knee point kp1 received from the user. Note that the maximum input level of the tone curve 501 is set to xmax.

[0050] Once the knee point kp1 is determined, the input signal level xp1 at the knee point kp1 on the tone curve 501 is determined. The knee slope ks1 at this time can be calculated using the following equation 1. ks1=(ymax−kp1) / (xmax−xp1) (Formula 1)

[0051] Similarly, if the input signal level at the knee point kp2 is xp2, the knee slope ks2 of the knee curve 2 can be calculated by the following equation 2. ks2=(ymax−kp2) / (xmax−xp2) (Formula 2)

[0052] By determining the knee compensation parameters in this way, the user can generate a knee slope that reaches the maximum output level ymax set by the user at the maximum input level xmax, without taking the maximum input level xmax into consideration.

[0053] In step S305, the correction curve generation unit 205 applies knee correction to the tone curve 501 based on the knee point received from the user in step S303 and the knee slope calculated in step S304, to generate a correction curve.

[0054] That is, tone curve 501 is used up to the input signal level xp1 or xp2 corresponding to the knee point, and above xp1 or xp2 corresponding to the knee point a correction curve (corrected tone curve) is generated using knee curve 1 or 2. Here, step S305 functions as a correction curve generation step that applies high-luminance side gradation correction to the tone curve to generate a correction curve.

[0055] In step S306, the correction curve application unit 207 applies the correction curve (corrected tone curve) generated by the correction curve generation unit 205 to the input image 201, and outputs the output image 208. Here, step S306 functions as a correction curve application step that applies the correction curve to the input image.

[0056] On the other hand, if it is determined in step S302 that automatic knee slope calculation is not to be applied, in step S307, the knee correction parameter acquisition unit 202 acquires the knee point of knee correction set (input) by the user and the knee slope set (input) by the user.

[0057] Fig. 6 is a diagram showing an example of a method for a user to set the knee point and knee slope according to embodiment 1. In the GUI screen 406 shown in Fig. 6, a section 601 that accepts on / off of automatic knee slope calculation is set to off, and as a result, it is determined in step S302 that automatic knee slope calculation correction is not to be applied.

[0058] By placing the cursor over each item on the left side of GUI screen 406 and entering a menu, the user can input (set) the value, for example, 85% in section 603 that accepts the knee point and +3 in section 604 that accepts the knee slope (the value of the slope). At this time, the output level (maximum output level of knee correction) in section 602 does not need to be input by the user, so it is displayed as not accepting input, as shown in FIG.

[0059] Using a GUI such as that shown in FIG. 6, the user can manually set the knee point and knee slope, and in step S307, the settings are acquired.

[0060] In step S308, the correction curve generation unit 205 generates a correction curve by applying knee correction to the tone curve 501 based on the knee point and knee slope parameters received from the user in step S307. That is, in step S308, if it is determined in step S302 that the calculation of the knee correction amount by the correction amount calculation means is not to be applied, a correction curve is generated in accordance with the knee slope and knee point parameters input by the user.

[0061] Specifically, tone curve 501 is used up to the input signal level corresponding to the knee point specified by the user, and above that, a correction curve (corrected tone curve) is generated that has a knee slope using the knee slope specified by the user.

[0062] Then, in step S306, the correction curve application unit 207 applies the correction curve (corrected tone curve) generated by the correction curve generation unit 205 to the input image 201, and outputs the output image 208.

[0063] As described above, according to this embodiment, it is possible to adjust appropriate parameters for knee correction without requiring the user to take into consideration the dynamic range of the input signal or the output signal level.

[0064] In this embodiment, the operation when the knee correction parameter acquisition unit 202 receives the maximum output level of knee correction from the user has been described, but a predetermined maximum output level may be stored in the RAM 204.

[0065] In addition, in the example shown in Fig. 4, an example of a GUI that does not accept knee slope setting from the user when automatic knee slope calculation is on has been described, but it is also possible to display a sentence such as "Knee slope is set automatically" as shown in Fig. 7. It is also possible to display that "automatic knee slope calculation is on" as shown in Fig. 7.

[0066] When the calculation of the knee correction amount by the correction amount calculation means is applied in this way, a message may be displayed indicating that the knee slope parameter will be calculated automatically.

[0067] <Embodiment 2> Next, a second embodiment of the present invention will be described. Note that a description of the same components as those in the first embodiment will be omitted. In the second embodiment, an operation for calculating the knee point level from the maximum output level and the knee slope will be described.

[0068] 8 is a flowchart showing an example of processing in a signal processing method according to the second embodiment, and shows an example of a processing method of the knee correction processing unit 200. Note that the operation of each step in the flowchart of FIG. 8 is performed sequentially by a CPU or the like serving as a computer in the system control unit 120 executing a computer program stored in a memory.

[0069] The processes in steps S801 and S805 to S808 are similar to the processes in steps S301 and S305 to S308 in the first embodiment, respectively, and therefore will not be described again.

[0070] In step S802, the correction curve application necessity acquisition unit 206 determines whether or not to apply automatic knee point calculation based on an instruction from the user. That is, it determines whether or not an instruction to apply automatic knee point calculation has been given by the user. If the determination is Yes, the process proceeds to step S803. If the determination is No, the process proceeds to step S807.

[0071] In step S803, the knee correction parameter acquisition unit 202 receives input (setting) of the maximum output level of knee correction and the knee slope from the user.

[0072] Fig. 9 is a diagram showing an example of a knee slope setting method according to the second embodiment, illustrating an example of the knee correction parameter acquisition unit 202. The GUI screen 406 in Fig. 9 has a section 901 for accepting on / off of automatic knee point calculation, and a section 902 for accepting an output level (maximum output level of knee correction). The GUI screen 406 further has a section 903 for accepting manual input (setting) of the knee point, and a section 904 for accepting a knee slope.

[0073] 9, when automatic knee point calculation is applied, the knee point receiving section 903 is displayed in such a way that it does not receive input from the user. That is, when it is determined in step S802 that automatic knee point calculation as the knee correction amount is to be applied, user input of knee point parameters is not received.

[0074] By placing the cursor on each item on the left side of the GUI screen 406 and entering the menu, a parameter setting screen 905 is displayed on the right side of the GUI screen 406, and adjustment parameters can be received from the user.

[0075] Using a GUI such as that shown in FIG. 9, the user can set the output level (maximum output level of knee correction) and knee slope, and in step S803, the settings are acquired.

[0076] In step S804, the knee correction amount calculation unit 203 calculates the value of the knee point from the output level (maximum output level of knee correction) and knee slope received from the user. The knee point kp1 in the example of Fig. 5 can be calculated by finding the intersection of knee curve 1 and tone curve 501.

[0077] Similarly, the knee point kp2 can be calculated by finding the intersection of the knee curve 2 and the tone curve 501. By determining the knee compensation parameters in this way, the user can apply knee compensation that reaches the maximum output level ymax set at the maximum input level xmax, without taking the maximum input level xmax into consideration.

[0078] Alternatively, the knee point may be defined as the point at which a straight line passing through a point determined by the maximum input point and maximum output point of the tone curve and having a slope set in 904 intersects with the tone curve on the low output level side. A knee curve (knee straight line) may be used above the knee point, and a correction curve using the tone curve may be generated below the knee point.

[0079] As described above, according to this embodiment, the parameters of the knee correction can be adjusted without requiring the user to take into consideration the dynamic range of the input signal or the output signal level.

[0080] While Fig. 9 illustrates a display example in which knee point setting is not accepted from the user when automatic knee point calculation is applied, it is also possible to display a message such as "Knee points are set automatically" as shown in Fig. 10. It is also possible to display that "automatic knee point calculation is on" as shown in Fig. 10.

[0081] When the calculation of the knee correction amount by the correction amount calculation means is applied in this way, a message may be displayed indicating that the knee point parameters will be calculated automatically.

[0082] Although the present invention has been described in detail above based on preferred embodiments, the present invention is not limited to the above embodiments. Various modifications and combinations of the above embodiments are possible based on the spirit of the present invention, and are not excluded from the scope of the present invention. Furthermore, the present invention includes those that realize the functions of the above embodiments using, for example, at least one processor or circuit such as a CPU. Furthermore, multiple processors may be used to perform distributed processing.

[0083] In order to realize some or all of the control in the above-described embodiments, a computer program that realizes the functions of the above-described embodiments may be supplied to an imaging device or the like via a network or various storage media. Then, a computer (or a CPU, MPU, or the like) in the imaging device or the like may read and execute the program. In this case, the program and the storage medium storing the program constitute the present invention. The present invention also includes the following combinations.

[0084] (Configuration 1) A signal processing device comprising: a storage means for storing data of a tone curve to be applied to an input image; a correction parameter acquisition means for acquiring a high-luminance side gradation correction parameter for adjusting the amount of correction of the high-luminance side gradation correction of the tone curve; a correction amount calculation means for calculating the amount of correction of the high-luminance side gradation correction based on the maximum output level of the tone curve and the high-luminance side gradation correction parameter so as to maintain the dynamic range of the tone curve; a correction curve generation means for applying the high-luminance side gradation correction to the tone curve to generate a correction curve; and a correction curve application means for applying the correction curve to the input image.

[0085] (Configuration 2) The signal processing device according to Configuration 1, further comprising a determination means for receiving and determining whether or not to apply the high-luminance-side gradation correction of the amount of correction calculated by the correction amount calculation means, and applying the correction curve to the input image when the determination means determines that the high-luminance-side gradation correction is to be applied.

[0086] (Configuration 3) The signal processing device according to configuration 1 or 2, characterized in that the high-brightness side gradation correction parameter is a parameter of knee correction to be applied to the tone curve, and is a parameter of either the knee point or the knee slope at which the knee correction starts.

[0087] (Configuration 4) The signal processing device according to Configuration 3, wherein the correction amount calculation means calculates the amount of knee correction based on the maximum output level and the knee correction parameters so as to maintain the dynamic range of the tone curve.

[0088] (Configuration 5) The signal processing device according to Configuration 4, wherein the correction amount calculation means generates the correction curve in accordance with the parameters of the knee slope and the knee point input by a user when the calculation of the knee correction amount by the correction amount calculation means is not applied.

[0089] (Configuration 6) The signal processing device according to Configuration 4 or 5, characterized in that the correction amount calculation means does not accept user input of either the knee slope or the knee point parameter when applying the calculation of the knee correction amount by the correction amount calculation means.

[0090] (Configuration 7) The signal processing device according to Configuration 6, wherein the correction amount calculation means displays a message indicating that either the parameter of the knee slope or the knee point is automatically calculated when the calculation of the knee correction amount by the correction amount calculation means is applied.

[0091] (Method) A signal processing method comprising: a correction parameter acquisition step of acquiring a high-luminance side gradation correction parameter for adjusting the maximum output level of a tone curve to be applied to an input image and the high-luminance side gradation correction level of said tone curve; a correction amount calculation step of calculating a correction amount of high-luminance side gradation correction based on said maximum output level and said high-luminance side gradation correction parameter so as to maintain the dynamic range of said tone curve; a correction curve generation step of applying said high-luminance side gradation correction to said tone curve to generate a correction curve; and a correction curve application step of applying said correction curve to said input image.

[0092] (Program) A computer program for controlling each means of the signal processing device according to any one of configurations 1 to 7 by a computer. [Explanation of symbols]

[0093] 112: Image processing unit 200: Knee correction processing section 202: Knee correction parameter acquisition unit 203: Knee correction amount calculation unit 204:RAM 205: Correction curve generation unit 206: Correction curve application necessity acquisition unit 207: Correction curve application section

Claims

1. a storage means for storing data of a tone curve to be applied to an input image; a correction parameter acquisition means for acquiring a high-luminance side gradation correction parameter for adjusting the amount of high-luminance side gradation correction of the tone curve; a correction amount calculation means for calculating the correction amount of the high-luminance side gradation correction based on the maximum output level of the tone curve and the high-luminance side gradation correction parameter so as to maintain the dynamic range of the tone curve; a correction curve generating means for generating a correction curve by applying the high-luminance side gradation correction to the tone curve; a correction curve applying means for applying the correction curve to the input image; A signal processing device comprising:

2. a determination unit that receives the correction amount calculated by the correction amount calculation unit and determines whether or not to apply the high-luminance side gradation correction, 2. The signal processing device according to claim 1, wherein when the determining means determines that the high-luminance side gradation correction is to be applied, the correction curve is applied to the input image.

3. 2. The signal processing device according to claim 1, wherein the high-luminance side gradation correction parameter is a parameter for knee correction applied to the tone curve, and is a parameter for either a knee point or a knee slope at which the knee correction starts.

4. 4. The signal processing device according to claim 3, wherein the correction amount calculation means calculates the amount of knee correction based on the maximum output level and the knee correction parameters so as to maintain the dynamic range of the tone curve.

5. 5. The signal processing device according to claim 4, wherein the correction amount calculation means generates the correction curve in accordance with parameters of the knee slope and the knee point input by a user when the calculation of the knee correction amount by the correction amount calculation means is not applied.

6. 5. The signal processing device according to claim 4, wherein the correction amount calculation means does not accept a user input of either the knee slope or the knee point parameter when applying the calculation of the knee correction amount by the correction amount calculation means.

7. 7. The signal processing device according to claim 6, wherein the correction amount calculation means displays a message indicating that a parameter of either the knee slope or the knee point is automatically calculated when the calculation of the knee correction amount by the correction amount calculation means is applied.

8. a correction parameter acquisition step of acquiring a high-luminance side gradation correction parameter for adjusting the maximum output level of a tone curve to be applied to an input image and the high-luminance side gradation correction level of the tone curve; a correction amount calculation step of calculating a correction amount of high-luminance side gradation correction based on the maximum output level and the high-luminance side gradation correction parameter so as to maintain the dynamic range of the tone curve; a correction curve generating step of generating a correction curve by applying the high-luminance side gradation correction to the tone curve; a correction curve applying step of applying the correction curve to the input image; A signal processing method comprising:

9. A computer program for controlling each means of the signal processing device according to any one of claims 1 to 7 by a computer.

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