JP2007164628A - Image processing device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the optimization of image processing at a high speed without causing an increase in a circuit scale. <P>SOLUTION: An image signal of a processing target is converted by using a table for conversion table for registering an output image signal value and image processing information for image processing about an input image signal value composed of a plurality of components. In the conversion of the image signal using the table for conversion processing, a processing parameter in an image processing circuit is set on the basis of the image processing information acquired from the table for conversion processing. Then, the image processing circuit with the processing parameter set on the basis of the image processing information processes the image signal converted by a converting means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to image processing using a lookup table.

In general, image processing such as sharpness correction, noise suppression, and contrast correction is known. In this type of image processing, the same processing is generally performed on the entire image, but in order to further improve the image quality, it has been proposed to perform image processing according to the region in the image signal. Yes. Patent Document 1 discloses a configuration in which the gain of an aperture correction signal is changed or the frequency characteristics are changed with respect to a human face region.
Japanese Patent Laid-Open No. 11-146405

  However, the method disclosed in Patent Document 1 requires an image processing circuit for detecting a skin color from a processing target image and discriminating a human face area, and avoids an increase in circuit scale and processing time. I can't. The same problem exists in a configuration in which image processing is performed in accordance with image characteristics from hue determination or pattern recognition of an image signal. Further, since only the human face area or specific area of the image signal is effective for improving the image quality, a sufficient effect is not obtained.

  SUMMARY An advantage of some aspects of the invention is that image processing can be appropriately adjusted without increasing the circuit scale.

In order to achieve the above object, an image processing apparatus according to an aspect of the present invention has the following arrangement. That is,
A conversion processing table in which output image signal values and image processing information for image processing are registered for input image signal values composed of a plurality of components;
Conversion means for converting an image signal to be processed using the conversion processing table;
Setting means for performing conversion of the image signal by the conversion means and setting processing parameters of the image processing means based on image processing information acquired from the conversion processing table;
And processing means for processing the image signal converted by the converting means by the image processing means in which processing parameters are set by the setting means.

According to another aspect of the present invention for solving the above problems, the following image processing method is provided. That is,
A conversion step of converting an image signal to be processed using a conversion processing table in which an output image signal value and image processing information for image processing are registered for an input image signal value composed of a plurality of components;
A setting step of performing conversion of the image signal by the conversion step and setting processing parameters of the image processing means based on image processing information acquired from the conversion processing table;
There is provided an image processing method including a processing step of processing the image signal converted in the conversion step by an image processing unit in which a processing parameter is set in the setting step.

  According to the present invention, the image processing parameters are set according to the color area of the image, so that it is possible to appropriately adjust the image processing without increasing the circuit scale.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a block diagram showing the configuration of the image processing apparatus according to this embodiment. In this embodiment, an image processing apparatus incorporated in a digital still camera will be described. However, the application of the present invention is not limited to this. For example, it may be realized in a general-purpose computer such as a personal computer, or may be realized in a digital video camera. Therefore, the image to be processed may be a video (moving image) or a still image. It is also possible to apply the image processing apparatus of this embodiment to a printer. Furthermore, part or all of the processing described below may be realized by hardware.

  The look-up table 101 is a look-up table that obtains a fifth-order output value for a third-order input value. At the same time, it performs color conversion of the input three-color image signal, and sets the image processing parameters to the control unit 105 and It outputs to a processing part (102-104). In the following description, “red (R), blue (B), green (G)” is used as the input / output image signal of the lookup table 101, but the present invention is not limited to this. For example, “luminance signal (Y), color difference signal Cr (R−Y), color difference signal Cb (B−Y)”, density signal composed of “cyan (Cy), magenta (Mg), yellow (Ye)”, etc. May be used as an input / output signal of the lookup table 101. In the above description, the color space representing the input color is three-dimensional. However, it is obvious that an image signal in a color space of four or more dimensions can be input / output. Further, the color space of the input / output signals of the lookup table 101 need not be the same. For example, a lookup table may be used in which RGB space values are used as input values and CMY space values are used as output values.

  The look-up table 101 converts the input three-color image signals Rin, Gin, and Bin into image signals Rout, Gout, and Bout, and outputs the image information Iout and the image quality setting value Pout. That is, in the case of the present embodiment, the lookup table 101 has a third order input value (Rin, Gin, Bin) and a fifth order output value (Rout, Gout, Bout, Iout, Pout). In the present embodiment, since application to a digital still camera is described, an image signal input to the look-up table 101 is transmitted to an optical system (not shown) including an imaging lens or an image sensor (not shown). It is the digital image signal obtained through this. Hereinafter, the image information Iout and the image quality setting value Pout are collectively referred to as image processing parameters.

  FIG. 6 is a diagram illustrating an example of encoding the image information Iout and the image quality setting value Pout. The image information Iout indicates image contents (skin, landscape, blue sky, etc.) corresponding to the color of the input value. The image quality setting value Pout indicates image processing parameters for a plurality of image processes such as a sharpness correction amount, a noise suppression amount, and a contrast correction amount. Image processing parameters expressed using encoded values as shown in FIG. 6 are registered in the lookup table 101. If the image information Iout is used, scene discrimination can be easily performed. For example, when the image information Iout is image content having a skin ratio of a certain value or more, the image information Iout is determined to be a portrait image.

  In the control unit 105, the CPU 105a executes various controls by executing a control program stored in the ROM 105b or the RAM 105c. The RAM 105c also functions as a work memory for the CPU 105a. For example, the control unit 105 sets image processing parameters for the sharpness correction unit 102, the noise suppression unit 103, and the contrast correction unit 104 based on image processing information (Iout, Pout) obtained from the lookup table 101. Do. The control unit 105 also has an image memory 105d for storing images. The control unit 105 sends an image from the image memory 105d to each circuit (102 to 104) for image processing, and stores the image processed image in the image memory 105d. The interface 105e is an interface between the lookup table 101, the circuits 102 to 104 and the units 106 to 108, and the CPU 105a.

  The sharpness correction unit 102 includes a plurality of bandpass filters, and performs sharpness correction by changing the frequency characteristics and gain of each bandpass filter. The noise suppression unit 103 detects a low frequency region by passing a color image signal through a predetermined bandpass filter, and suppresses noise by removing a high frequency component in the low frequency region. The contrast correction unit 104 prepares a plurality of gamma correction coefficients for the luminance signal and performs contrast correction.

  The image display unit 106 displays an input image, an output image, current processing settings, and the like under the control of the control unit 105. The operation unit 107 inputs user instructions such as designation of an input image and start of processing. When this image processing apparatus is applied to a digital video camera or a digital still camera, an operation for inputting an image to be processed (shutter operation, recording operation, etc.) is also performed by the operation unit 107. The recording unit 108 records and stores the processed image. That is, color conversion is performed by the lookup table 101, image processing is performed based on the image processing information acquired from the lookup table 101, and the image stored in the image memory 105d is recorded in the recording unit 108 by the control unit 105. . Note that a removable recording medium may be used for the storage unit 108.

  FIG. 2 is a diagram showing a five-dimensional lookup table 101 according to the present embodiment. The look-up table 101 converts the input three-color image signals Rin, Gin, and Bin into three-color image signals Rout, Gout, and Bout, and outputs an image quality setting value Pout and image information Iout. Only either Pout or Iout may be output. Alternatively, as shown in FIG. 3, the image processing parameter Qout calculated by the image processing parameter calculation unit 301 based on Pout and the change amount of the input value and the output value may be output. In this case, the value of Qout is supplied to the circuits 102 to 104 as image processing circuits, for example, as a processing intensity setting parameter. For example, when | Rin−Rout | + | Gin−Gout | + | Bin−Bout | exceeds a predetermined value, the level of color conversion is large, and noise such as tone jump is likely to occur. Therefore, in such a case, the image quality can be further improved by weakening the sharpness correction of the processing intensity setting parameter and enhancing the noise suppression regardless of Pout.

  Next, an image processing parameter setting method will be described. The lookup table 101 of the present embodiment inputs three color input image signals Rin, Gin, Bin having a gradation of 8 bits per color. Then, output image signals Rout, Gout, Bout having a gradation of 8 bits per color, image information Iout having an information amount of 3 bits, and an image processing parameter Pout having an information amount of 5 bits are output. Therefore, the accuracy of 24 bits for input and 32 bits for output is required. The lookup table 101 of the present embodiment uses a 64 Mbyte RAM having a 24-bit address space. That is, the lookup table 101 is realized by assigning input signal values to a 24-bit address space and assigning output signal values to a 32-bit storage area.

  FIG. 4 schematically shows a lookup table. In order to simplify the drawing, nine grid points are shown on each side, but the lookup table 101 of this embodiment has 257 grid points on each side. Each grid point stores a table value having a data length of 32 bits. Color conversion output values, image information, and image quality setting values are written in advance in all 64 Mbytes recording areas of the look-up table RAM. Writing data into the RAM for the look-up table only needs to be performed when the image processing apparatus is started up or when the image processing content is changed. During image processing, only reading to the storage area is performed, thereby eliminating image processing time. It becomes possible.

  FIG. 5 schematically shows an example of setting image processing parameters. In FIG. 5, an area 502 indicates a skin color area, and an encoded value (“000”) representing “skin” as image information is associated with the input image signal in this area as a lookup table 101 ( RAM). Further, in the lookup table 101, in order to prevent the facial wrinkles from being emphasized in correspondence with the input image signal in the area 502, a parameter (for example, a sharpness correction weaker than the normal area and a contrast weakened). “00000” in FIG. 6 is stored. Of course, the image quality setting value can be freely set in the region 502 in accordance with the color density, luminance, and the like.

  A region 501 surrounded by a thick line in FIG. 5 is a green region represented by a leaf of a landscape image. This area 501 is a color area that requires a higher resolution than the normal area and is less sensitive to noise. Therefore, an image quality setting value that suppresses the noise suppression amount and that sharpness correction is strongly applied is registered in the lookup table so as to correspond to the region 501. Although not shown in FIG. 5, the image quality setting value that maximizes the amount of noise suppression is registered because the blue sky or purple color gamut is a color area that is particularly sensitive to noise.

  In the image processing apparatus as described above, when a color image signal is input as an input image signal, each pixel value (Rin, Gin, Bin) of the input image signal is converted into a pixel value (Rout) of the output image signal by the lookup table 101. , Gout, Bout). At this time, image information (Iout) and image quality setting value (Pout) are output according to the input pixel value.

  In accordance with the image quality setting value output from the look-up table 101, for example, a parameter indicating processing intensity is set for the sharpness correction circuit 102, the noise suppression circuit 103, and the contrast correction circuit 104. Then, image processing by the sharpness correction circuit 102, the noise suppression circuit 103, and the contrast correction circuit 104 is executed on the image converted by the lookup table 101, and the result is stored in the image memory 105d. For example, output pixels and image processing parameters are sequentially output to the look-up table 101 according to the input pixel sequence of the input image signal. In the circuits 102 to 104, parameter setting is performed based on the image processing parameter output together with the output pixel serving as the target pixel. In this way, the output image converted using the lookup table 101 is processed according to the parameter value output from the lookup table 101.

  FIG. 7 is a flowchart for explaining the operation of the image processing apparatus according to the present embodiment (that is, the processing content of the control unit 105). In step S701, a signal is input for each pixel from the input image signal. In step S702, the input pixel value is converted by referring to the lookup table 101 to obtain a converted pixel value, and an image processing parameter is acquired. In step S703, the processing parameters of the image processing units (circuits 102 to 104 in FIG. 1) are set based on the image processing parameters acquired in step S702. Next, in step S704, the image processing unit in which the processing parameter is set in step S703 executes image processing using the pixel as the target pixel, and in step S705, the converted image after image processing is output. Here, the output includes, for example, storage in the image memory 105d and storage in the recording unit 108. Of course, the image information may be output to the outside of the apparatus. The processes in steps S701 to S705 are executed for all the pixels of the input image (step S706). When filtering using surrounding pixel values is performed in the image processing in step S704, the converted pixel values and image processing parameters acquired in step S702 are appropriately buffered, and the parameters and pixels are stored in the image processing unit. The value may be supplied.

  As described above, according to the present embodiment, it is possible to execute appropriate image processing according to the color area of the input image. In the present embodiment, in order to realize appropriate image processing, it is necessary to increase an area for storing image processing parameters such as image information and image quality setting values as compared with a general lookup table. However, image processing optimization can be dealt with mainly by increasing the storage area, and there is almost no increase in the image processing circuit scale. Therefore, according to this embodiment, optimization of image processing can be realized at high speed without increasing the circuit scale.

  In FIG. 1, the circuits 102 to 104 may be realized by software. In this case, for example, the control unit 105 converts the input image signal using the lookup table 101. Then, image processing is executed while setting parameters of a program for performing sharpness correction processing, noise suppression processing, and contrast correction processing according to the image processing parameters acquired from the lookup table 101 in this conversion processing.

  Therefore, the present invention achieves the functions of the above-described embodiments by supplying a software program directly or remotely to a system or apparatus, and the computer of the system or apparatus reads and executes the supplied program code. Including the case. In this case, the supplied program is a program corresponding to the flowchart shown in the drawing in the embodiment.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the present invention includes a computer program itself for realizing the functional processing of the present invention.

  In that case, as long as it has the function of a program, it may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, or the like.

  Examples of the recording medium for supplying the program include the following. For example, floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM, DVD (DVD-ROM, DVD- R).

  As another program supply method, a client computer browser is used to connect to a homepage on the Internet, and the computer program of the present invention is downloaded from the homepage to a recording medium such as a hard disk. In this case, the downloaded program may be a compressed file including an automatic installation function. It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer is also included in the present invention.

  Further, the program of the present invention may be encrypted, stored in a storage medium such as a CD-ROM, and distributed to users. In this case, a user who has cleared a predetermined condition is allowed to download key information for decryption from a homepage via the Internet, execute an encrypted program using the key information, and install the program on the computer. You can also.

  In addition to the functions of the above-described embodiment being realized by the computer executing the read program, the embodiment of the embodiment is implemented in cooperation with an OS or the like running on the computer based on an instruction of the program. A function may be realized. In this case, the OS or the like performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

  Furthermore, the program read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, so that part or all of the functions of the above-described embodiments are realized. May be. In this case, after a program is written in the function expansion board or function expansion unit, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing based on the instructions of the program.

It is a block diagram which shows the structure of the image processing apparatus by this embodiment. It is a figure explaining the lookup table by this embodiment. It is a figure explaining the lookup table by this embodiment. It is a figure which illustrates typically the part for the color conversion of a lookup table. It is a figure which illustrates typically the setting method of an image processing parameter. It is a figure which shows the encoding example of an image quality setting value and image information. It is a flowchart explaining operation | movement of the image processing apparatus by this embodiment.

Claims (12)

A conversion processing table in which output image signal values and image processing information for image processing are registered for input image signal values composed of a plurality of components;
Conversion means for converting an image signal to be processed using the conversion processing table;
Setting means for performing conversion of the image signal by the conversion means and setting processing parameters of the image processing means based on image processing information acquired from the conversion processing table;
An image processing apparatus comprising: processing means for processing the image signal converted by the conversion means by the image processing means in which processing parameters are set by the setting means. The image processing means includes sharpness correction means,
The image processing apparatus according to claim 1, wherein the setting unit sets a sharpness correction amount of the sharpness correction unit by setting the processing parameter. The image processing means includes noise suppression means,
The image processing apparatus according to claim 1, wherein the setting unit sets a noise suppression amount of the noise suppression unit by setting the processing parameter. The image processing means includes a contrast correction means,
The image processing apparatus according to claim 1, wherein the setting unit sets a contrast correction amount of the contrast correction unit by setting the processing parameter.   The image processing apparatus according to claim 1, further comprising a changing unit that changes the image processing information according to a change amount of an input value and an output value of the lookup table. A conversion step of converting an image signal to be processed using a conversion processing table in which an output image signal value and image processing information for image processing are registered for an input image signal value composed of a plurality of components;
A setting step of performing conversion of the image signal by the conversion step and setting processing parameters of the image processing means based on image processing information acquired from the conversion processing table;
And a processing step of processing the image signal converted in the conversion step by an image processing unit in which a processing parameter is set in the setting step. The image processing means includes sharpness correction means,
The image processing method according to claim 6, wherein the setting step sets a sharpness correction amount of the sharpness correction unit by setting the processing parameter. The image processing means includes noise suppression means,
The image processing method according to claim 6, wherein the setting step sets a noise suppression amount of the noise suppression unit by setting the processing parameter. The image processing means includes a contrast correction means,
The image processing method according to claim 6, wherein the setting step sets a contrast correction amount of the contrast correction unit by setting the processing parameter.   The image processing method according to claim 6, further comprising a changing step of changing the image processing information according to a change amount of an input value and an output value of the lookup table.   A control program for causing a computer to execute the image processing method according to claim 6.   A computer-readable medium storing the control program according to claim 11.

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