JP2014110624A - Image processing device, image processing method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform edge emphasis while suppressing influences of noise, and to improve an image quality.SOLUTION: An image processing device comprises: a contrast calculation part detecting a contrast of an input image to calculate a contrast value corresponding to the detected contrast; a plurality of edge detectors detecting edge components in frequency bands different from each other independently of each other, to the input image; a plurality of gain adjustment parts provided so as to correspond to the plurality of edge detectors respectively, and each performing gain adjustment depending on the contrast value to the edge component detected by the corresponding edge detector; a plurality of smoothing processing parts provided so as to correspond to the plurality of gain adjustment parts respectively, and each smoothing the detected edge component; and an image correction part performing edge emphasis processing to the input image on the basis of output values respectively outputted from the plurality of smoothing processing parts.

Description

  The present invention relates to an image processing apparatus, an image processing method, and a program.

  The contour correction processing that enhances the sharpness of an image by enhancing the contour component of the image is an effective process for improving the image quality of a digital image, for example, an image captured by a digital still camera. Therefore, conventionally, various techniques have been proposed for edge enhancement processing for enhancing the contour component of an image.

  For example, in Patent Document 1 below, as the conversion condition for converting the intensity of the contour component, the slope of the change in the value of the output data with respect to the change in the value of the input data (gain) as the value of the input data increases. ) Is reduced so that the intensity of the contour component is greatly increased for non-edge portions with low contrast in the original image, while edge portions with high contrast in the original image are used. A technique for suppressing an increase in the strength of the contour component has been proposed.

  In Patent Document 2 below, image quality is improved by performing edge enhancement processing and smoothing processing on the edge gradient direction where the gradient of the pixel value is the largest and the edge direction orthogonal to the edge gradient direction, respectively. A technique has been proposed in which edge gradient directions and edge directions are detected based on different characteristics, edge enhancement processing and smoothing processing are performed for each characteristic, and then the processing results of the characteristics are combined.

JP 2006-129176 A JP 2006-221403 A

  The technique described in Patent Document 1 is a method for controlling the gain of edge enhancement based on the contrast of an image. However, with the technique described in Patent Document 1, there is a concern that noise in a low contrast region may be emphasized.

  Further, the technique described in Patent Document 2 is a method of detecting an edge having a plurality of different characteristics, performing enhancement / smoothing processing, and integrating the results to improve the image quality. However, when integrating the results of applying emphasis / smoothing processing for each characteristic to the image, if an edge direction misjudgment or the like occurs, even if there is a result that can be correctly determined by other characteristics, there is an adverse effect. There is a problem that it cannot be ignored. Further, although the reliability in the edge direction is calculated and used as a parameter for blending the results, there is a problem that it is based on the difference value between adjacent pixels and is easily influenced by noise and cannot be expected to have a great effect.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to perform image processing that can improve image quality by performing edge enhancement while suppressing the influence of noise. An apparatus, an image processing method, and a program are provided.

  In order to solve the above problems, according to an aspect of the present invention, a contrast calculation unit that detects a contrast of an input image and calculates a contrast value corresponding to the detected contrast, and the input image, A plurality of edge detectors that detect edge components independently of each other in different frequency bands, and the edge components detected by the corresponding edge detectors provided corresponding to each of the plurality of edge detectors And a plurality of gain adjustment units that perform gain adjustment according to the contrast value, and a plurality of smoothing processes that are provided corresponding to each of the plurality of gain adjustment units and smooth the detected edge component And an edge enhancement process on the input image based on output values respectively output from the plurality of smoothing processing units and the plurality of smoothing processing units. Image processing apparatus comprising an image correcting unit, the performing is provided.

  According to this configuration, the contrast calculation unit detects the contrast of the input image, calculates a contrast value corresponding to the detected contrast, and the plurality of edge detection units have different frequency bands for the input image. The edge components are detected independently of each other, and the plurality of gain adjustment units are provided corresponding to the plurality of edge detection units, respectively, and contrast with respect to the edge components detected by the corresponding edge detection unit. The gain adjustment is performed according to the value, and a plurality of smoothing processing units are provided corresponding to each of the plurality of gain adjusting units to smooth the detected edge component, and the image correction unit is connected to the plurality of smoothing processing units. Based on each output value, edge enhancement processing is performed on the input image. Thus, edge enhancement can be performed while suppressing the influence of noise, and image quality can be improved.

  The smoothing processing unit preferably specifies the direction of the detected edge component and then calculates a weighted average of the direction of the edge component to smooth the edge component. This makes it possible to perform edge enhancement while suppressing noise components and oblique line jaggies.

  The image correction unit calculates the sum of output values output from the plurality of smoothing processing units to obtain an edge enhancement amount, and performs edge enhancement processing by adding the edge enhancement amount to the input image. It is preferable. Thereby, it is possible to improve the image quality while reducing the influence of noise.

  Each of the plurality of gain adjustment units preferably performs the gain adjustment according to different gain correction curves and the contrast value. As a result, gain adjustment can be performed for each frequency component extracted in a plurality of paths based on the contrast of the surrounding area, and image quality can be improved while reducing the influence of noise.

  When the image size changing process is performed after the edge enhancement process, the plurality of gain adjusting units change the characteristics of the corresponding gain correction curve according to the image size changing process, and then the gain Adjustments may be made. As a result, the image after the image size changing process can be maintained in high quality.

  In order to solve the above-described problem, according to another aspect of the present invention, a contrast calculation step of detecting a contrast of an input image and calculating a contrast value corresponding to the detected contrast, the input image On the other hand, an edge detection step for detecting edge components independently from each other in different frequency bands, and gain adjustment according to the contrast value for the detected edge components in the different frequency bands are independent of each other. And the gain adjustment step performed in the different frequency bands, the smoothing processing step of smoothing the detected edge components independently of each other, and the output values respectively output in the smoothing processing step, An image correction step for performing edge enhancement on the input image; An image processing method comprising is provided.

  According to such a configuration, in the contrast calculation step, the contrast of the input image is detected, and a contrast value corresponding to the detected contrast is calculated. In the edge detection step, the input image is mutually compared in different frequency bands. Edge component detection is performed independently, and in the gain adjustment step, gain adjustment according to the contrast value is independently performed on the detected edge components in different frequency bands, and a smoothing processing step In the frequency bands different from each other, the detected edge components are smoothed independently of each other, and in the image correction step, edge enhancement is performed on the input image based on the output values respectively output in the smoothing processing step. Processing is performed. Thus, edge enhancement can be performed while suppressing the influence of noise, and image quality can be improved.

  In order to solve the above problem, according to still another aspect of the present invention, a contrast calculation function for detecting a contrast of an input image in a computer and calculating a contrast value corresponding to the detected contrast, A plurality of edge detection functions for detecting edge components independently of each other in different frequency bands from the input image, and the corresponding edge detection functions provided corresponding to each of the plurality of edge detection functions A plurality of gain adjustment functions for performing gain adjustment according to the contrast value and the plurality of gain adjustment functions are provided corresponding to the edge components detected by A plurality of smoothing processing functions for smoothing and output values output from the plurality of smoothing processing functions, respectively. And Zui, a program for implementing an image correcting function of performing edge enhancement processing to the input image is provided.

  According to this configuration, the computer can function as the image processing apparatus.

  As described above, according to the present invention, the gain adjustment processing is performed independently from each other in different frequency bands, and the effect of noise is suppressed by performing the edge enhancement processing by integrating the processing results in each frequency band. Edge enhancement can be performed while improving image quality.

1 is a block diagram illustrating an example of a configuration of an imaging apparatus according to a first embodiment of the present invention. FIG. 2 is a block diagram illustrating an example of a configuration of an image processing unit according to the embodiment. It is the block diagram which showed an example of the structure of the edge emphasis part which concerns on the same embodiment. It is explanatory drawing for demonstrating the edge emphasis part which concerns on the same embodiment. It is explanatory drawing for demonstrating the edge emphasis part which concerns on the same embodiment. It is explanatory drawing for demonstrating the edge emphasis part which concerns on the same embodiment. It is the flowchart which showed an example of the flow of the imaging method which concerns on the embodiment. It is explanatory drawing for demonstrating an Example.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

(First embodiment)
<Configuration of image processing apparatus>
The configuration of the image processing apparatus according to the first embodiment of the present invention will be described in detail below with reference to FIGS. In the following description, the image processing apparatus according to the present embodiment is described as an example where the image processing apparatus is realized as an imaging apparatus capable of imaging a subject.

  FIG. 1 is a block diagram showing an example of the configuration of the image processing apparatus according to the present embodiment. As shown in FIG. 1, the image processing apparatus 10 according to the present embodiment that functions as an imaging apparatus includes a CPU / DSP 101, a ROM, 103, a RAM 105, an imaging optical system 107, an imaging element 109, an optical system driving unit 111, and an image. A processing unit 113, a projection light source 115, a display control unit 117, an LCD / EVF 119, an operation interface (I / F) 121, an operation unit 123, a recording medium I / F 125, a recording medium 127, and the like are mainly provided.

  A CPU (Central Processing Unit) / DSP (Digital Signal Processor) 101 functions as an arithmetic processing unit and a control unit. According to various programs recorded in the ROM 103, the RAM 105, etc., the entire operation in the imaging apparatus 10 or a part thereof is performed. Control. A ROM (Read Only Memory) 103 stores programs used by the CPU / DSP 101, operation parameters, and the like. A RAM (Random Access Memory) 105 temporarily stores programs used by the CPU / DSP 101, parameters that change as appropriate during execution of the programs, and the like. These are connected to each other by a bus constituted by an internal bus such as a CPU bus.

  The CPU / DSP 101, ROM 103, RAM 105, and the like cooperate with each other to automatically control the autofocus (AF) of the image pickup apparatus 10, the AE unit that controls automatic exposure (AE), and the white balance. An AWB unit or the like is realized.

  The imaging optical system 107 causes light from a subject to enter a light receiving surface of an imaging element 109 (to be described later) under drive control by an optical system driving unit 111 (to be described later). Thereby, in the image sensor 109, the light incident on the light receiving surface is converted into an electric signal, and a captured image is generated. The imaging optical system 107 includes, for example, a lens group such as a zoom lens and a focus lens, an aperture, a shutter, an ND filter, and the like.

  Light guided by the imaging optical system 107 (including ambient light, flash light, and the like) is incident on the light receiving surface of the imaging element 109 provided at the subsequent stage of the imaging optical system 107. The image sensor 109 has a light receiving surface on which light receiving elements are arranged in a two-dimensional shape, and converts light incident on the light receiving surface into an electrical signal corresponding to the light amount. By sequentially reading out this electrical signal for each pixel constituted by one or a plurality of light receiving elements, an image corresponding to the incident light is generated. Note that the timing at which the pixel signal is reset in the image sensor 109 and the timing at which the pixel signal is read out are controlled by the optical system driving unit 111 described later. In the imaging device 10 according to the present embodiment, the type of the imaging element 109 is not particularly limited, and a known imaging element such as a CMOS sensor or a CCD sensor can be used. The electrical signal (that is, the captured image) generated by the image sensor 109 is output to the image processing unit 113 described later.

  The optical system driving unit 111 is a processing unit that performs driving control of members such as a lens group, a diaphragm, a shutter, and an ND filter that configure the imaging optical system 107 and the imaging element 109. The optical system driving unit 111 controls the focal position of the lens group, the opening / closing degree of the aperture, the opening / closing timing of the shutter, the readout timing of the image sensor 109, and the like, and a captured image obtained by capturing the subject is generated. It becomes. The specific configuration of the optical system driving unit 111 is not particularly limited, and any known technique can be used.

  The image processing unit 113 performs various types of image processing including known pre-processing and post-processing on the captured image generated by the image sensor 109. The image processing unit 113 can also perform compression processing for compressing the captured image generated by the image sensor 109. Furthermore, the image processing unit 113 according to the present embodiment performs edge enhancement processing as will be described in detail below on the captured image captured by the image sensor 109. The detailed configuration of the image processing unit 113 will be described in detail below.

  The light projecting light source 115 is a light source of various types of light that is projected when the subject is imaged. As such a projection light source 115, for example, a xenon light source used as flash light, a light source provided in advance in an imaging device for autofocus (AF), a light source provided in advance for red-eye correction, or the like is used. Can be mentioned.

  The display control unit 117 performs display control of a display device such as an LCD (Liquid Crystal Display) or EVF (Electronic View Finder) described later. As a result, a captured image, a menu screen for selecting various functions provided in the imaging device 10, and the like are displayed on the display screen of the display device.

  The LCD and EVF function as a display device provided in the imaging device 10, and the display content is controlled by the display control unit 117. The user of the imaging device 10 can check the captured image on the spot or select various menus by viewing the contents displayed on the display screens of these display devices.

  The operation I / F 121 is an interface for inputting information (operation information) related to various operations performed by the user to the operation unit 123 such as a hard key or a dial to the imaging apparatus 10. Various operation information input from the operation I / F 121 is notified to the CPU / DSP 101, and various functions corresponding to the operation information are realized. The configuration of the operation unit 123 is not particularly limited, and a known input unit such as an operation unit using a touch panel or the like can be applied.

  The recording medium I / F 125 is an interface for connecting a recording medium 127 to be described later to the imaging apparatus 10 and also functions as a driver for driving the recording medium 127. The recording medium 127 is an example of an external storage device provided in the imaging device 10. The recording medium I / F 125 can write various data to the recording medium 127 and read various data from the recording medium 127. In addition, the recording medium I / F 125 can display various data recorded on the recording medium 127 on a display device 119 such as an LCD or EVF in cooperation with the display control unit 117. In the present embodiment, the type of the recording medium 127 is not particularly limited, and various known recording media can be used. Further, the type of the recording medium I / F 125 can be appropriately selected according to the type of the recording medium 127.

<Configuration of image processing unit>
Next, a detailed configuration of the image processing unit 113 according to the present embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is a block diagram illustrating an example of the configuration of the image processing unit according to the present embodiment, and FIG. 3 is a block diagram illustrating an example of the configuration of the edge enhancement unit according to the present embodiment.

  As illustrated in FIG. 2, the image processing unit 113 included in the image processing apparatus 10 according to the present embodiment includes an edge enhancement unit 131 and a post-processing unit 133.

  The edge enhancement unit 131 is a processing unit that performs the edge enhancement processing according to the present embodiment on the captured image output from the image sensor 109. The edge emphasizing unit 131 refers to a storage unit such as the ROM 103, the RAM 105, the recording medium 127, and the like when executing the edge emphasis process described in detail below, and stores a program stored in the storage unit and a gain correction curve described later. Can be used. The detailed configuration and function of the edge enhancement unit 131 will be described in detail below.

  The post-processing unit 133 performs a known post-processing including image size change processing such as image size enlargement / reduction, as necessary, on a captured image that has been subjected to edge enhancement processing by the edge enhancement unit 131 and improved sharpness. Process. Further, the post-processing unit 133 can also perform processing such as compression of the captured image and conversion of the color coordinate space. The post-processing unit 133 can use various programs stored in the storage unit by referring to the storage unit such as the ROM 103, the RAM 105, and the recording medium 127 when performing the various processes as described above.

  The captured image that has been subjected to known post-processing by the post-processing unit 133 is displayed on the display device 119 such as an LCD or EVF via the display control unit 117, or stored in the recording medium 127 via the recording medium I / F 125. Or

  Next, the configuration of the edge enhancement unit 131 according to the present embodiment will be described in more detail with reference to FIG.

  The edge enhancement unit 131 according to the present embodiment includes a contrast calculation unit 151, a plurality of edge detection units 153, a plurality of gain adjustment units 155, a plurality of smoothing processing units 157, and an image correction unit 159. Hereinafter, these processing units will be described in detail.

  In FIG. 3, the case where two edge detection units 153, gain adjustment units 155, and smoothing processing units 157 are provided is shown as an example. However, the number of processing units is not limited to the following two examples, and the number of edge detection units 153 and gain adjustment units 155 is not limited to the required processing accuracy, the size of a filter used for processing, and the like. What is necessary is just to determine suitably according to a calculation cost etc.

  When the contrast calculation unit 151 acquires the captured image (hereinafter also referred to as an input image) input to the edge enhancement unit 131, the contrast calculation unit 151 detects the contrast of the input image and calculates a contrast value corresponding to the detected contrast. . The contrast value calculation process can be performed using a known contrast value calculation method. For example, the size of the edge detection filter used in the plurality of edge detection units 153 described below (in other words, In accordance with the size of the edge detection area, the following equation 101 is applied to the edge detection area.

Here, in the following expression 101, “contrast” represents a contrast value, and P _ij represents the pixel value of the (vertical, horizontal) = (i, j) th pixel constituting the input image, and is an edge detection region. The case where the size of is 5 × 5 is shown. Therefore, the following expression 101 is a difference between the maximum pixel value and the minimum pixel value in the edge detection region having a size of 5 × 5 as a contrast value.

・・・（式１０１）

... (Formula 101)

  Note that when the contrast calculation unit 151 calculates the contrast value using the formula 101, the second pixel value from the maximum value and the maximum value and the minimum value in the edge detection region are not used, and The contrast value may be calculated using the second pixel value from the minimum value.

  The contrast calculation unit 151 outputs the contrast value of each edge detection region calculated in this way to each of a plurality of edge detection units 153 described later.

  The plurality of edge detection units 153 detect edge components independently of each other in different frequency bands from the input image input to the edge enhancement unit 131. In the example illustrated in FIG. 3, the first edge detection unit 153 a and the second edge detection unit 153 b have different frequency bands, for example, a relatively low band in the spatial frequency plane representing the contour of the object, and the details of the object. Edge detection is performed independently in each of the relatively high bands in the spatial frequency plane representing

  More specifically, the first edge detection unit 153a and the second edge detection unit 153b first select two different frequency filters (for example, different spatial frequency bands as shown in FIG. Classification is performed by using either of two types of bandpass filters having different bands. For example, when the first edge detection unit 153a performs edge detection for a relatively low frequency band and the second edge detection unit 153b performs edge detection for a relatively high frequency band, the first edge detection unit 153a separates the frequency band using a bandpass filter as shown in FIG. 4, and the second edge detector 153b separates the frequency band using a bandpass filter as shown in FIG. Further, a high pass filter may be used instead of the band pass filter for the high frequency band.

  Thereafter, the first edge detection unit 153a and the second edge detection unit 153b perform edge detection processing independently of each other using a two-dimensional edge detection filter having a predetermined size for each spatial frequency band. Such a two-dimensional edge detection filter is not particularly limited, and for example, a 5 × 5 two-dimensional FIR (Finite Impulse Response) filter, a 7 × 7 two-dimensional FIR filter, or the like may be used. Is possible.

  Information (for example, the output value of the FIR filter) regarding edges detected independently of each other by the respective edge detection units 153 is output to a plurality of gain adjustment units 155 described later.

  In which frequency band the first edge detection unit 153a and the second edge detection unit 153b perform edge detection processing is not particularly limited.

  The plurality of gain adjustment units 155 are provided corresponding to each of the plurality of edge detection units 153, and the contrast calculated by the contrast calculation unit 151 for the edge component detected by the corresponding edge detection unit 153. Adjust the gain according to the value.

  More specifically, in the present embodiment, as shown in FIG. 3, a first gain adjustment unit 155a is provided corresponding to the first edge detection unit 153a, and corresponding to the second edge detection unit 153b. A second gain adjustment unit 155b is provided.

  First, the first gain adjustment unit 155a and the second gain adjustment unit 155b each acquire a gain correction curve set in advance corresponding to each gain adjustment unit. These gain correction curves have, for example, different correction curve shapes as illustrated in FIG. For example, in the first gain correction curve shown in FIG. 5, in the region where the contrast value is low, the correction coefficient value is close to 1, and the correction coefficient value decreases as the contrast value increases. It is like that. On the other hand, in the second gain correction curve shown in FIG. 5, the value of the correction coefficient is close to 1 up to an intermediate contrast value, and the correction coefficient suddenly decreases in a region where the contrast value is high. It has become a thing.

  In areas where the contrast value is high, the sharpness such as the contour of the object is originally relatively high. Therefore, by using the two types of gain correction curves shown in FIG. 5, in the high contrast value region, it becomes possible to weaken the edge enhancement relative to the low contrast value region, thereby suppressing excessive edge enhancement. It becomes possible. Moreover, since gain adjustment is performed using gain correction curves having different shapes, different gain control can be performed for different spatial frequency bands.

  Note that the shape of each gain correction curve is not limited to the example shown in FIG. 5, and can be determined as appropriate according to the policy of gain adjustment.

  The first gain adjustment unit 155a and the second gain adjustment unit 155b determine a correction coefficient based on each gain correction curve and the contrast value as described above, and output the output value output from the corresponding edge detection unit. The gain value is calculated by multiplying the correction coefficient determined in the above.

  The first gain adjustment unit 155a and the second gain adjustment unit 155b output information on the calculated gain value to a plurality of smoothing processing units 157 described later.

  Depending on the setting conditions of the image processing apparatus 10 and the like, it is determined in advance that the post-processing unit 133 provided at the subsequent stage of the edge emphasizing unit 131 performs image size changing processing such as input image enlargement / reduction processing. There may be cases. In such a case, each gain adjustment unit 155 changes the characteristics of the corresponding gain correction curve in accordance with the image size change process, and then performs the gain adjustment as described above (that is, the gain value calculation process). ) May be performed. It can be said that the image size changing process is a process of changing the spatial frequency of the input image of interest. Accordingly, each gain adjustment unit 155 may perform processes such as “correct the gain correction curve so as to weaken the degree of gain suppression”, “correct the gain correction curve so as to enhance the gain”, and the like. By performing such processing, it is possible to maintain high image quality after changing the image size.

  The plurality of smoothing processing units 157 are provided corresponding to each of the plurality of gain adjustment units 155, and are detected by the corresponding edge detection unit 153, and the edge component whose gain is adjusted by the gain adjustment unit 155. , Smoothing processing is performed.

  More specifically, in the present embodiment, as shown in FIG. 3, a first smoothing processing unit 157a is provided corresponding to the first edge detection unit 153a and the first gain adjustment unit 155a, and the second edge A second smoothing processing unit 157b is provided corresponding to the detection unit 153b and the second gain adjustment unit 155b.

  The first smoothing processing unit 157a and the second smoothing processing unit 157b specify the direction of the edge component output from the corresponding gain adjustment unit 155, and then calculate a weighted average of the direction of the edge component to obtain the edge component. Smooth. This makes it possible to perform edge enhancement while suppressing noise components such as isolated point noise. In addition, since it is possible to improve edge connectivity, it is possible to perform edge enhancement in which jaggies that are likely to occur in oblique lines are suppressed (not noticeable).

  Hereinafter, the smoothing process (smoothing process) performed by each of the first smoothing processing unit 157a and the second smoothing processing unit 157b will be specifically described with reference to FIG.

The first smoothing processing unit 157a and the second smoothing processing unit 157b use the direction determination operator D _n (n = 0 to 3) shown in the upper part of FIG. 6 to obtain edge components (for example, 3 × 3) after gain adjustment. The direction of the edge component) is determined. More specifically, the first smoothing processing unit 157a and the second smoothing unit 157b, to the edge component of interest, by the action of the direction determination operator D _n, to obtain the corresponding calculated value. On top of that, the first smoothing processing unit 157a and the second smoothing unit 157b includes a direction corresponding to the direction determination operator D _n giving the maximum calculated value is determined to be the direction of the edge components.

Then, the first smoothing processing unit 157a and the second smoothing processing unit 157b, as shown in the lower part 6, by using the index of the direction determination operator D _n giving the maximum calculated value (n), the index Select a smoothing operator. Thereafter, the first smoothing processing unit 157a and the second smoothing processing unit 157b cause the selected smoothing operator to act on the focused edge component to obtain an output value. The first smoothing processing unit 157a and the second smoothing processing unit 157b output the obtained output value to the subsequent image correction unit 159 as a processing result of the smoothing processing.

  The image correction unit 159 performs edge enhancement processing on the input image based on the output values output from the plurality of smoothing processing units 157, respectively. More specifically, as shown in FIG. 3, the image correction unit 159 calculates the sum of output values respectively output from the plurality of smoothing processing units 157 as an edge enhancement amount, and inputs the calculated edge enhancement amount. Edge enhancement processing is performed by adding to the image. Thereby, it is possible to improve the image quality while reducing the influence of noise.

  Heretofore, an example of the function of the image processing apparatus 10 according to the present embodiment has been shown. Each component described above may be configured using a general-purpose member or circuit, or may be configured by hardware specialized for the function of each component. In addition, the CPU or the like may perform all functions of each component. Therefore, it is possible to appropriately change the configuration to be used according to the technical level at the time of carrying out the present embodiment.

  It should be noted that a computer program for realizing each function of the image processing apparatus according to the present embodiment as described above can be produced and installed in a personal computer or the like. In addition, a computer-readable recording medium storing such a computer program can be provided. The recording medium is, for example, a magnetic disk, an optical disk, a magneto-optical disk, a flash memory, or the like. Further, the above computer program may be distributed via a network, for example, without using a recording medium.

<Flow of image processing method>
Next, the flow of the image processing method in the image processing apparatus 10 according to the present embodiment will be briefly described with reference to FIG. FIG. 7 is a flowchart showing an example of the flow of the image processing method according to the present embodiment.

  In the image processing method according to the present embodiment, first, the edge enhancement unit 131 acquires a processing target image (that is, the input image in FIG. 3) (step S101). Thereafter, the contrast calculation unit 151 of the edge enhancement unit 131 calculates the contrast value of the processing target image (step S103).

  Further, the plurality of edge detection units 153 provided in the edge enhancement unit 131 respectively detect edge components in different frequency bands (for example, high frequency band and mid frequency band) (step S105). Thereafter, each edge detection unit 153 outputs the obtained detection result to the gain adjustment unit 155 provided at the subsequent stage of each edge detection unit 153.

  Subsequently, in each of the gain adjustment units 155 provided at the subsequent stage of each edge detection unit 153, the gain of each frequency band (for example, the high frequency band / mid frequency band) is adjusted (step S107). Thereafter, each gain adjustment unit 155 outputs the edge component after gain adjustment to the smoothing processing unit 157 provided at the subsequent stage of each gain adjustment unit 155.

  Next, each smoothing processing unit 157 performs a smoothing process on the edge component after gain adjustment (for example, the edge component of the high frequency band / mid frequency band) output from each gain adjustment unit 155 (Step S1). Thereafter, each smoothing processing unit 157 outputs the obtained processing result to the image correction unit 159 provided in the subsequent stage.

  The image correction unit 159 calculates an edge enhancement amount based on the output result output from each smoothing processing unit 157 (step S111). Thereafter, the image correction unit 159 enhances the edge of the processing target image by adding the calculated edge enhancement amount to the processing target image (step S113). Thereby, edge enhancement is performed, and an image with improved sharpness is generated. Thereafter, the image correction unit 159 outputs the processing target image after edge enhancement (step S113).

  By performing such processing, edge enhancement can be performed while suppressing the influence of noise, and image quality can be improved.

<Example>
FIG. 8 shows an edge image obtained by performing an edge enhancement process using the image processing method according to the present embodiment, using an image of a side mirror of a car as an input image. In this processing, edge enhancement processing is performed by using an edge enhancement section having a configuration as shown in FIG.

  As shown in FIG. 8A, after the general edge enhancement processing, the contour of the side mirror is jagged, whereas as shown in FIG. 8B, the edge according to the present embodiment. It can be seen that the contours of the side mirrors are smoothly connected by performing the enhancement process.

  As described above, by using the image processing apparatus and the image processing method according to the present embodiment, it is possible to provide a high-quality image with improved sharpness without conspicuous over-emphasis of an object outline or jaggy of oblique lines. Is possible.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

10 Imaging device 101 CPU / DSP
103 ROM
105 RAM
DESCRIPTION OF SYMBOLS 107 Image pick-up optical system 109 Image pick-up element 111 Optical system drive part 113 Image processing part 115 Light projection light source 117 Display control part 119 Display apparatus (LCD / EVF)
121 Operation interface (operation I / F)
123 Operation unit 125 Recording media interface (recording media I / F)
127 Recording medium 131 Edge enhancement unit 133 Post processing unit 151 Contrast calculation unit 153 Edge detection unit 153a First edge detection unit 153b Second edge detection unit 155 Gain adjustment unit 155a First gain adjustment unit 155b Second gain adjustment unit 157 Smoothing processing Unit 157a first smoothing processing unit 157b second smoothing processing unit 159 image correction unit

Claims (7)

A contrast calculation unit that detects the contrast of the input image and calculates a contrast value corresponding to the detected contrast;
A plurality of edge detectors that detect edge components independently of each other in different frequency bands with respect to the input image;
A plurality of gain adjustment units provided corresponding to each of the plurality of edge detection units, and performing gain adjustment according to the contrast value for the edge components detected by the corresponding edge detection unit;
A plurality of smoothing processing units provided corresponding to each of the plurality of gain adjustment units and smoothing the detected edge component;
An image correction unit that performs edge enhancement processing on the input image based on output values respectively output from the plurality of smoothing processing units;
An image processing apparatus comprising: 2. The smoothing processing unit according to claim 1, wherein the smoothing processing unit smoothes the edge component by calculating a weighted average of the direction of the edge component after specifying the direction of the detected edge component. 3. Image processing device. The image correction unit calculates the sum of output values output from the plurality of smoothing processing units to obtain an edge enhancement amount, and performs edge enhancement processing by adding the edge enhancement amount to the input image. The image processing apparatus according to claim 1, wherein the image processing apparatus is an image processing apparatus. 4. The image processing according to claim 1, wherein each of the plurality of gain adjustment units performs the gain adjustment according to different gain correction curves and the contrast value. 5. apparatus. When the image size changing process is performed after the edge enhancement process, the plurality of gain adjusting units change the characteristics of the corresponding gain correction curve according to the image size changing process, and then the gain The image processing apparatus according to claim 4, wherein adjustment is performed. A contrast calculating step for detecting a contrast of the input image and calculating a contrast value corresponding to the detected contrast;
An edge detection step for detecting edge components independently of each other in different frequency bands from the input image;
A gain adjustment step of performing gain adjustment according to the contrast value independently of each other on the detected edge components in the different frequency bands;
Smoothing processing steps for smoothing the detected edge components independently from each other in the different frequency bands;
An image correction step for performing edge enhancement processing on the input image based on the output values respectively output in the smoothing processing step;
An image processing method comprising: On the computer,
A contrast calculation function for detecting the contrast of the input image and calculating a contrast value corresponding to the detected contrast;
A plurality of edge detection functions for detecting edge components independently of each other in different frequency bands from the input image;
A plurality of gain adjustment functions that are provided corresponding to each of the plurality of edge detection functions, and that perform gain adjustment according to the contrast value for the edge components detected by the corresponding edge detection functions;
A plurality of smoothing processing functions provided corresponding to each of the plurality of gain adjustment functions, and smoothing the detected edge component;
An image correction function for performing edge enhancement processing on the input image based on output values respectively output from the plurality of smoothing processing functions;
A program to realize

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