JP2010062836A - Image processing apparatus, image processing method, and image processing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus etc., that suitably reproduces sensation of granularity of a silver halide photograph. <P>SOLUTION: A synchronization processing unit 23 performs synchronization processing for generating image data having a plurality of colors for each pixel, on the basis of image data obtained by an imaging device which has an imaging element, having a plurality of color filters arranged. Addition units 36 and 37 add a prescribed granular pattern to the image data, having been subjected to the synchronization processing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for adding a granular pattern such as that obtained by a silver salt photograph to image data obtained by a digital camera or the like.

  A digital image obtained by a digital camera or the like is superimposed with a noise component that mainly generates an image sensor, and this noise component is a cause of deterioration in image quality. In general, efforts are made to improve image quality by reducing noise components superimposed on an image by various methods.

  In silver halide photography, granular noise is mainly caused by silver salt particles, which is one of the causes of image quality deterioration as in digital images. Conversely, the graininess due to granular noise is There is also the fact that it has a certain value as an expression of photography.

Under such a background, in order to obtain the visual effect of silver salt particles in order to give a digital image the same value as a silver salt photograph, a technology that superimposes a granular pattern resembling the graininess of silver salt particles on the digital image Various proposals have been made. For example, in Patent Document 1, random numbers are generated in units of pixels, and frequency filtering and scale change are performed to superimpose the expected granularity on the image. In Patent Document 2, a granular pattern is calculated by subtracting a smoothed image from an exposure image obtained from a uniformly exposed color film.
US Pat. No. 5,641,596 Japanese Patent Laid-Open No. 11-85955

  However, although the above Patent Documents 1 and 2 refer to calculation of the granularity or granular pattern to be superimposed, the image processing method necessary for generating the granular feeling expected as the final image is completely described. Absent.

  An object of this invention is to provide the technique for reproducing the graininess of a silver salt photograph appropriately.

  An image processing apparatus according to an aspect of the present invention is configured to simultaneously generate image data having a plurality of colors per pixel based on image data obtained by an imaging apparatus having an imaging element in which a plurality of color filters are arranged. A processing unit, and a granular pattern adding unit that adds a predetermined granular pattern to the image data generated by the synchronization processing unit.

  An image processing method according to another aspect of the present invention is a step of generating image data having a plurality of colors per pixel based on image data obtained by an imaging device having an imaging device in which a plurality of color filters are arranged. And a step of adding a predetermined granular pattern to the generated image data.

  An image processing program according to yet another aspect of the present invention generates image data having a plurality of colors per pixel based on image data obtained by an imaging apparatus having an imaging element in which a plurality of color filters are arranged. A program for causing a computer to execute a step and a step of adding a predetermined granular pattern to the generated image data.

  According to the present invention, since the process of adding a granular pattern to the image data after the synchronization process is performed, the synchronization process is performed after the granular pattern is added. It is possible to appropriately reproduce the graininess of a silver halide photograph by preventing problems such as loss of image quality, or recognizing a granular pattern as the structure of an image and generating a geometric pattern that is not originally present in an image.

  FIG. 1 is a block diagram illustrating a configuration of a digital camera including an image processing apparatus according to an embodiment. This digital camera includes an imaging unit 1, an A / D conversion unit 2, a microcomputer 3 (hereinafter referred to as a microcomputer 3), a RAM 4, a ROM 5, an image processing circuit 6, an operation unit 7, and a display unit. 8, a memory interface 9 (hereinafter referred to as I / F 9), and a recording medium 10.

  The image pickup unit 1 includes a single-plate color image pickup device (hereinafter simply referred to as an image pickup device) in which a plurality of color filters are arranged in front of a photodiode constituting each pixel, a photographing optical system, and a drive unit thereof. It is composed of For example, the color filters are arranged in a Bayer array. The Bayer array has a line in which R pixels and G (Gr) pixels are alternately arranged in a horizontal direction, and a line in which G (Gb) pixels and B pixels are alternately arranged, and the two lines are further divided. It is configured by alternately arranging in the vertical direction. The image sensor receives light collected by a lens (not shown) by a photodiode that constitutes a pixel and photoelectrically converts the light, and outputs the amount of light to the A / D converter 2 as a charge amount. The image sensor may be either a CMOS type or a CCD type. Further, the color filter may be configured in an array other than the Bayer array, or may be configured in a color other than R, G, and B.

  The A / D converter 2 converts the electrical signal output from the imaging unit 1 into a digital image signal (hereinafter referred to as image data).

  The microcomputer 3 is a control unit that performs overall control of the digital camera. For example, the microcomputer 3 controls the focus control of the imaging optical system inside the imaging unit 1, the exposure control of the imaging device, the recording control when recording the image data on the recording medium 10, and the display when displaying the image data on the display unit 8. Control and so on.

  The RAM 4 is a storage unit that temporarily stores various data such as image data obtained by the A / D conversion unit 2 and image data processed by an image processing circuit 6 described later. The ROM 5 stores various parameters necessary for the operation of the digital camera, granular pattern data resembling the granular feeling due to silver salt particles, and the like. The granular pattern data is obtained by a known method, separated into a Y (luminance) component and a C (color) component, and stored in the ROM 5. The ROM 5 also stores various programs executed by the microcomputer 3. The microcomputer 3 reads parameters necessary for various sequences from the ROM 5 in accordance with a program stored in the ROM 5 and executes each process.

  The image processing circuit 6 performs various image processing on the image data read from the RAM 4. Details of the image processing performed by the image processing circuit 6 will be described later. The image data that has been subjected to image processing by the image processing circuit 6 is recorded on the recording medium 10 via the I / F 9. The recording medium 10 is, for example, a recording medium composed of a memory card that can be attached to and detached from the digital camera body, but is not limited to this.

  The operation unit 7 is an operation member such as a power button, a release button, and various input keys. When one of the operation members of the operation unit 7 is operated by the user, the microcomputer 3 executes various sequences corresponding to the user's operation. The power button is an operation member for instructing power on / off of the digital camera. When the power button is pressed, the microcomputer 3 turns the digital camera on or off. The release button has a two-stage switch of a first release switch and a second release switch. When the release button is pressed halfway and the first release switch is turned on, the microcomputer 3 performs a shooting preparation sequence such as AE processing and AF processing. In addition, when the release button is fully pressed and the second release switch is turned on, the microcomputer 3 executes the shooting sequence to perform shooting. The operation unit 7 can also set an image recording mode and a shooting mode.

  The bus 11 is a transfer path for transferring various data generated in the digital camera to each unit in the digital camera. The bus 11 is connected to the imaging unit 1, the A / D conversion unit 2, the microcomputer 3, the RAM 4, the ROM 5, the image processing circuit 6, the operation unit 7, the display unit 8, and the I / F 9. Yes.

  FIG. 2 is a block diagram showing a detailed configuration of the image processing circuit 6. The image processing circuit 6 includes a first noise reduction unit (first NR unit in the figure) 21, a white balance correction unit (WB unit in the figure) 22, a synchronization processing unit 23, a color conversion unit 24, a floor, Tone conversion unit 25, YC conversion unit 26, edge extraction unit 27, edge enhancement unit 28, Y gradation conversion unit 29, Y second noise reduction unit (Y second NR unit in the figure) 30, C Tone conversion unit 31, C second noise reduction unit (C second NR unit in the figure) 32, resizing unit 33, JPEG compression unit 34, JPEG decompression unit 35, addition units 36 and 37, multiplication Parts 38 and 39.

  The first noise reduction unit 21 performs a process for reducing noise on the image data converted by the A / D conversion unit 2 and stored in the RAM 4 based on a noise reduction gain NR1 described later. This noise reduction process is a process for correcting pixel defects of the image sensor and a process for reducing random noise generated during imaging. However, at least one of a process for correcting pixel defects of the image sensor and a process for reducing random noise generated during imaging may be performed.

  The white balance correction unit 22 performs a process of correcting the white balance of the image data after noise reduction.

  The synchronization processing unit 23 performs a process of synchronizing image data based on the Bayer array into image data including R, G, and B information per pixel. The synchronized image data is subjected to predetermined color conversion processing by the color conversion unit 24 and then subjected to gradation conversion processing (first gradation conversion processing) by the gradation conversion unit 25.

  The YC conversion unit 26 converts the image data after the gradation conversion process into a Y (luminance) signal and a C (color) signal. The converted Y signal is output to the adder 36, and the C signal is output to the adder 37.

  The edge extraction unit 27 performs processing for extracting an edge from the image data on which the noise reduction processing has been performed by the first noise reduction unit 21. The edge emphasizing unit 28 performs edge emphasis processing that multiplies the edge data extracted by the edge extracting unit 27 by a predetermined gain.

  The multiplication unit 38 multiplies the Y component data of the granular pattern stored in the ROM 5 by a gain GRN_Y described later and outputs the result to the addition unit 36. The addition unit 36 adds the edge data input from the edge enhancement unit 28 and the Y component data of the granular pattern input from the multiplication unit 38 to the Y signal. The Y signal is input from the YC conversion unit 26 during shooting and RAW data editing, and is input from the RAM 4 during JPEG compression data editing. The Y signal output from the adder 36 is subjected to a tone conversion process (second tone conversion process), which will be described later, in the Y tone converter 29 and then reduced in noise by the Y second noise reduction unit 30. Processing is performed.

  The multiplier 39 multiplies the C component data of the granular pattern stored in the ROM 5 by a gain GRN_C described later, and outputs the result to the adder 37. The addition unit 37 adds the C component data of the granular pattern input from the multiplication unit 39 to the C signal. The C signal is input from the YC conversion unit 26 during shooting and RAW data editing, and is input from the RAM 4 during JPEG compression data editing. The C signal output from the adding unit 37 is subjected to a tone conversion process (second tone conversion process) described later in the C tone conversion unit 31 and then reduced in noise by the C second noise reduction unit 32. Processing is performed.

  The resizing unit 33 resizes the Y signal and C signal after the noise reduction processing according to the image size at the time of recording. The JPEG compression unit 34 performs JPEG compression on the resized Y signal and C signal. The data after JPEG compression is recorded on the recording medium 10 via the I / F 9. The JPEG decompression unit 35 performs decompression processing for reading JPEG compressed data recorded on the recording medium 10 and returning it to the state before compression.

= Processing flow during shooting =
3A and 3B are flowcharts showing a processing flow at the time of shooting by a digital camera including the image processing apparatus according to the embodiment. When the release button is turned on by the user, the process of step S10 is started.

  In step S10, known photometry processing and distance measurement processing are executed, and in subsequent step S20, known exposure control and focus control are executed. In step S <b> 30, an imaging process is executed in the imaging unit 1. In step S <b> 40, after the imaging process is executed by the imaging unit 1, the image data obtained by performing the A / D conversion process by the A / D conversion unit 2 is temporarily stored in the RAM 4.

  In step S50, it is determined whether the image recording format is the JPEG format or the RAW format. The image recording format can be set by the user operating the operation unit 7 before shooting. If it is determined that the image recording format is the JPEG format, the process proceeds to step S60. If it is determined that the image recording format is the RAW format, the process proceeds to step S250 in FIG. 3B.

  In step S60, it is determined whether the image recording mode is the silver salt tone mode or the normal mode. The silver salt tone mode is a mode in which a granular pattern resembling the granular feeling of silver salt particles is superimposed on image data in order to obtain a visual effect similar to that of a silver salt photograph. The image recording mode can be set by the user operating the operation unit 7 before shooting. If it is determined that the image recording mode is the normal mode, the process proceeds to step S70.

  In step S70, the noise reduction gain NR1 in the normal mode is calculated. FIG. 4 is a diagram illustrating an example of various gains, imaging noise, and image noise in the normal mode. For various gains, the gain NR1 used when the first noise reduction unit 21 performs noise reduction, the gain GRN_Y multiplied by the Y component of the granular pattern, the gain GRN_C multiplied by the C component of the granular pattern, and the Y second noise reduction unit 30 , The gain NR2_Y used when the noise reduction process is performed, and the gain NR2_C used when the C second noise reduction unit 32 performs the noise reduction process.

  Various gains are determined according to ISO sensitivity set at the time of shooting. For example, when the ISO sensitivity is 800, the gain NR1 is 4, the gain NR2_Y is 2, and the gain NR2_C is 2. However, in the normal mode, since the process of superimposing the granular pattern on the image data is not performed, the fields of the gains GRN_Y and GRN_C are blank. Note that the gains GRN_Y and GRN_C may be set to 0, and the process of superimposing the granular pattern may be performed.

  The imaging noise corresponding to each ISO sensitivity is based on the imaging noise in the case of ISO sensitivity 100, and the smaller the value, the greater the noise. That is, as the ISO sensitivity increases, the imaging noise increases. Similarly, the image noise is based on the image noise when the ISO sensitivity is 100, and the smaller the value, the larger the noise. Accordingly, the image noise increases as the ISO sensitivity increases.

  The ROM 5 stores a data table in which various gains corresponding to each ISO sensitivity as shown in FIG. 4 are stored. The data table is read and a gain NR1 corresponding to the ISO sensitivity at the time of shooting is calculated. To do. Note that the greater the value of the gain NR1, the greater the noise reduction effect during the noise reduction process.

  On the other hand, if it is determined in step S60 that the image recording mode is the silver salt tone mode, the process proceeds to step S80. In step S80, the noise reduction gain NR1 in the silver salt tone mode is calculated. FIG. 5 is a diagram illustrating an example of various gains, imaging noise, and image noise in the silver salt tone mode. In FIG. 5, various gains, imaging noise, and image noise are viewed in the same way as in FIG.

  In the silver salt tone mode, in order to keep the granularity on the finally obtained image data constant regardless of the ISO sensitivity, the intensity of the granular pattern to be synthesized (in accordance with the amplification of imaging noise in accordance with the ISO sensitivity) Gain GRN_Y, GRN_C) and noise reduction intensity (gain NR2_Y, NR2_C) after the granular pattern synthesis are controlled. Here, as the ISO sensitivity increases, the gains GRN_Y and GRN_C are reduced to reduce the intensity of the granular pattern to be combined with the image data. As shown in FIG. 5, the image noise of the image data after adding the granular pattern is constant regardless of the ISO sensitivity.

  Further, in order to maintain the granularity of the granular pattern superimposed on the image data, the gains NR2_Y and NR2_C are set weaker than in the normal mode. Furthermore, the intensity of the granular pattern is such that the color difference (C) is weakened relative to the luminance (Y), so that color noise is not unnecessarily generated.

  The ROM 5 stores a data table in which various gains corresponding to the ISO sensitivity as shown in FIG. 5 are stored. The data table is read to calculate the gain NR1 corresponding to the ISO sensitivity at the time of shooting. .

  In step S90, the first noise reduction unit 21 reads the image data stored in the RAM 4, and performs noise reduction processing using the noise reduction gain NR1 calculated in step S70 or step S80.

  In step S100, the white balance correction unit 22 performs a process of correcting the white balance on the image data after the noise reduction process. In step S110, the synchronization processing unit 23 performs synchronization processing, and in step S120, the color conversion unit 24 performs color conversion processing.

  In step S130, the tone conversion unit 25 performs tone conversion processing. Here, in consideration of the gamma characteristic of the display unit 8, gradation conversion processing is performed such that the dark part is expanded and the bright part is compressed. FIG. 7 is a diagram illustrating an example of gradation conversion characteristics when the gradation conversion process is performed in step S130. When the gradation conversion process is performed, the process proceeds to step S140 in FIG. 3B.

  In step S140, the YC conversion unit 26 converts the image data after the gradation conversion process into a Y (luminance) signal and a C (color) signal.

  In step S150, it is determined whether the image recording mode is the silver salt tone mode or the normal mode. This determination is the same as the determination in step S60. If it is determined that the image recording mode is the normal mode, the process proceeds to step S210. If it is determined that the image recording mode is the silver salt tone mode, the process proceeds to step S160.

  In step S160, gains GRN_Y and GRN_C in the silver salt tone mode are calculated. In calculating the gains GRN_Y and GRN_C, the data table as shown in FIG. 5 described above is read from the ROM 5, and the gains GRN_Y and GRN_C corresponding to the ISO sensitivity at the time of shooting are calculated.

  In step S170, the multiplication unit 38 reads the Y component data of the granular pattern from the ROM 5, and multiplies the read G component data of the granular pattern by the gain GRN_Y calculated in step S160. Further, the multiplication unit 39 reads the granular component C component data from the ROM 5 and multiplies the read granular pattern C component data by the gain GRN_C calculated in step S160.

  In step S180, the addition unit 36 adds the edge data input from the edge enhancement unit 28 and the Y component data of the granular pattern input from the multiplication unit 38 to the Y signal converted by the YC conversion unit 26. . Further, the addition unit 37 adds the C component data of the granular pattern input from the multiplication unit 39 to the C signal converted by the YC conversion unit 26.

  In step S190, the Y gradation conversion unit 29 reads the Y signal gradation conversion table from the ROM 5, and the C gradation conversion unit 31 reads the C signal gradation conversion table from the ROM 5.

  FIG. 8 is a diagram illustrating an example of gradation conversion characteristics when performing Y signal gradation conversion processing. This gradation conversion characteristic is a characteristic that enhances the contrast of image data, that is, a characteristic that compresses a dark part and a bright part and expands a halftone. FIG. 9 is a diagram illustrating an example of gradation conversion characteristics when performing gradation conversion processing of the C signal. The ROM 5 stores a gradation conversion table having gradation conversion characteristics as shown in FIG. 8 and a gradation conversion table having gradation conversion characteristics as shown in FIG. When the gradation conversion table is read from the ROM 5, the process proceeds to step S200.

  In step S200, the Y gradation conversion unit 29 performs gradation conversion processing on the Y signal input from the addition unit 36 using the Y signal gradation conversion table read in step S190. In the C gradation conversion unit 31, gradation conversion processing is performed on the C signal input from the addition unit 37 using the C signal gradation conversion table read in step S 190.

  In step S210, the Y second noise reduction unit 30 performs noise reduction processing on the Y signal after the tone conversion processing, and the C second noise reduction unit 32 performs C processing after the tone conversion processing. A process for reducing noise is performed on the signal. In the noise reduction process, gains NR2_Y and NR2_C corresponding to the normal mode or the silver salt tone mode are used. For example, if it is determined in step S150 that the normal mode is selected, a data table as shown in FIG. 4 is read from the ROM 5, and gains NR2_Y and NR2_C corresponding to the ISO sensitivity at the time of shooting are obtained. If it is determined in step S150 that the silver salt tone mode is selected, a data table as shown in FIG. 5 is read from the ROM 5, and gains NR2_Y and NR2_C corresponding to the ISO sensitivity at the time of shooting are obtained. The Y second noise reduction unit 30 performs noise reduction processing of the Y signal using the gain NR2_Y, and the C second noise reduction unit 32 performs noise reduction processing of the C signal using the gain NR2_C.

  In step S220, the resizing unit 33 resizes the Y signal and C signal after the noise reduction processing according to the image size at the time of recording. In step S230, the JPEG compression unit 34 performs JPEG compression on the resized Y signal and C signal. In step S240, the Y signal and the C signal compressed with JPEG are stored in the RAM 4.

  In step S250, shooting information such as an image recording mode and exposure conditions is created as fill header information. In step S260, the created file header information is JPEG compressed and added to data temporarily stored in RAM4. Then, recording is performed on the recording medium 10 via the I / F 9.

= Processing flow when editing RAW data =
In the flowchart showing the processing flow at the time of photographing shown in FIG. 3A, if it is determined in step S50 that the image recording format is the RAW format, the image processing after step S60 is not performed, and the recording medium 10 is processed as RAW data. To be recorded. In the following, processing in the case where image processing is performed by reading RAW data recorded on the recording medium 10 will be described.

  FIG. 10 is a flowchart showing a processing flow when editing RAW data. In the flowchart of FIG. 10, steps that perform the same processes as those in the flowchart of FIG. 3A are assigned the same step numbers, and detailed descriptions thereof are omitted. Moreover, since the process after step S130 of FIG. 10 is the same as the process of the flowchart shown to FIG. 3B, a figure and description are abbreviate | omitted.

  In step S1000, RAW image data is read from the recording medium 10 via the I / F 9. In step S1010, shooting information is read from the file header information added to the image data. In step S40, the read image data and shooting information are stored in the RAM 4.

  The processing after step S60 is the same as the processing of the flowcharts shown in FIGS. 3A and 3B.

= Processing when editing JPEG compressed data =
In the flowchart showing the processing flow at the time of photographing shown in FIGS. 3A and 3B, when it is determined that the image recording mode is the normal mode in the determinations in step S60 and step S150, the image data includes granular particles of silver salt particles. Granular patterns that resemble the feeling are not superimposed. Below, the process which reads the image data recorded in normal mode at the time of imaging | photography, superimposes the granular pattern resembling the granular feeling by silver salt particle | grains, and records on the recording medium 10 is demonstrated.

  FIG. 11 is a flowchart showing a processing flow when editing JPEG compressed data. In the flowchart of FIG. 11, steps that perform the same processes as the processes performed in the flowcharts of FIGS. 3A, 3 </ b> B, and FIG.

  In step S1100, JPEG-compressed image data is read from the recording medium 10 via the I / F 9.

  In step S1110, the JPEG decompression unit 35 performs decompression processing for returning the image data read in step S1100 to the state before JPEG compression. The image data subjected to the decompression process and the shooting information read out in step S1010 are stored in the RAM 4 in step S40.

  In step S1120, the image data stored in the RAM 4 is displayed on the display unit 8. Thereby, the user can confirm the image on which the granular pattern is superimposed.

  In step S160A, gains GRN_Y and GRN_C in the silver salt tone mode when editing JPEG compressed data are calculated. FIG. 6 is a diagram illustrating an example of a data table used in the processing when editing JPEG compressed data. In FIG. 6, various gains, imaging noise, and image noise are viewed in the same way as in FIGS. 4 and 5.

  When editing JPEG compressed data, in order to obtain an image quality equivalent to the image quality obtained during the shooting process in the silver salt tone mode, the intensity of the granular pattern (GRN_Y, GRN_C) and noise reduction strength after synthesis (NR2_Y, NR_C) are controlled.

  The ROM 5 stores a data table in which various gains corresponding to the ISO sensitivity as shown in FIG. 6 are stored. The data table is read and gains GRN_Y and GRN_C corresponding to the ISO sensitivity at the time of shooting are stored. calculate.

  In step S210A, the Y second noise reduction unit 30 performs noise reduction processing on the Y signal after the tone conversion processing, and the C second noise reduction unit 32 performs C processing after the tone conversion processing. A process for reducing noise is performed on the signal. Here, a data table as shown in FIG. 6 is read from the ROM 5, and gains NR2_Y and NR2_C corresponding to the ISO sensitivity at the time of shooting are obtained. The Y second noise reduction unit 30 performs noise reduction processing of the Y signal using the obtained gain NR2_Y, and the C second noise reduction unit 32 performs noise reduction processing of the C signal using the obtained gain NR2_C. Do.

  As described above, according to the image processing apparatus in the embodiment, the processing for adding a predetermined granular pattern is performed after the synchronization processing is performed on the image data. Therefore, the synchronization processing is performed after the granular pattern is added. This eliminates the problem of losing the fine granularity unique to silver salt particles, or recognizing the granular pattern as the structure of an image and generating a geometric pattern that is not in the original image. Can be properly reproduced.

  In addition, according to the image processing apparatus in the embodiment, the first gradation conversion process is performed on the image data subjected to the synchronization process, and the predetermined granular pattern is applied to the image data after the gradation conversion process Is added. Thus, by performing the gradation conversion process after adding the granular pattern, it is possible to prevent the granular pattern in the dark portion from being emphasized and the granular feeling to be impaired.

  Furthermore, according to the image processing apparatus in the embodiment, the second gradation conversion process different from the first gradation conversion process is performed on the image data to which the granular pattern is added. It is possible to achieve both characteristics and graininess control according to the gradation level. Since this second gradation conversion process is a gradation conversion process that enhances the contrast of image data, while suppressing the graininess of highlights and shadows, A unique grainy feel can be expressed.

  In addition, according to the image processing apparatus in one embodiment, an edge used in edge enhancement processing is extracted from image data before a predetermined granular pattern is added. When processing to extract an edge from image data after adding a granular pattern, there is a possibility that a part that is not an edge will be mistakenly extracted as an edge, but by extracting an edge from image data before adding a granular pattern, , It is possible to prevent erroneous extraction of edges.

  Further, according to the image processing apparatus in one embodiment, the intensity of the granular pattern added to the image data is adjusted, so that a desired granular pattern can be added. In particular, since the intensity of the granular pattern is adjusted according to the photographing sensitivity at the time of photographing, an appropriate granular pattern can be added in consideration of a noise component generated according to the photographing sensitivity.

  In the above description of the embodiment, an example in which the image processing apparatus is applied to a digital still camera has been described. However, a computer may execute a program for realizing the processing described in the embodiment. it can. That is, in a computer having a main storage device such as a CPU and a RAM and a computer-readable storage medium storing a program for realizing all or part of the processing described in the embodiment, the CPU is stored in the storage medium. By reading the stored program and executing information processing / calculation processing, processing similar to that of the above-described image processing apparatus is realized.

  Here, the computer-readable recording medium refers to a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, and the like. Further, the above-described program may be distributed to a computer via a communication line, and the computer that has received the distribution may execute the program.

  The present invention is not limited to the above-described embodiment, and various modifications and applications can be made without departing from the gist of the present invention. For example, the gains GRN_Y and GRN_C for determining the intensity of the granular pattern to be added to the image data are obtained according to the ISO sensitivity at the time of shooting. However, the user can set an arbitrary value by operating the operation unit 7. You may be able to do it. According to this method, a granular pattern having the intensity desired by the user can be added to the image data. Further, gains GRN_Y and GRN_C for determining the intensity of the granular pattern may be set according to the degree of noise on the image.

  In the above-described embodiment, the image data is described as being JPEG-compressed. However, the image data compression method is not limited to the JPEG format.

1 is a block diagram illustrating a configuration of a digital camera including an image processing apparatus according to an embodiment. It is a block diagram which shows the detailed structure of an image processing circuit. It is a flowchart which shows the front | former stage of the processing flow at the time of imaging | photography with the digital camera containing the image processing apparatus which concerns on one Embodiment. It is a flowchart which shows the back | latter stage of the processing flow at the time of imaging | photography with the digital camera containing the image processing apparatus which concerns on one Embodiment. It is a figure which shows an example of the various gains, imaging noise, and image noise in normal mode. It is a figure which shows an example of the various gains, imaging noise, and image noise in a silver salt tone mode. It is a figure which shows an example of the various gains at the time of JPEG compression data editing, imaging noise, and image noise. It is a figure which shows an example of the gradation conversion characteristic of the gradation conversion process performed before synthesize | combining a granular pattern. It is a figure which shows an example of the gradation conversion characteristic at the time of performing the gradation conversion process of Y signal. It is a figure which shows an example of the gradation conversion characteristic at the time of performing the gradation conversion process of C signal. It is a flowchart which shows the processing flow at the time of editing of RAW data. It is a flowchart which shows the processing flow at the time of edit of JPEG compression data.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Imaging part, 2 ... A / D conversion part, 3 ... Microcomputer, 4 ... RAM, 5 ... ROM, 6 ... Image processing circuit, 7 ... Operation part, 8 ... Display part, 9 ... I / F, 10 ... Recording Medium 21. First noise reducing unit 22 White balance correcting unit 23 Synchronizing unit 24 Color converting unit 25 Tone converting unit 26 YC converting unit 27 Edge extracting unit 28 ... Edge emphasis part, 29 ... Y gradation conversion part, 30 ... Y second noise reduction part, 31 ... C gradation conversion part, 32 ... C second noise reduction part, 33 ... Resize part, 34 ... JPEG compression part, 35 ... JPEG decompression unit, 36 ... addition unit, 37 ... addition unit, 38 ... multiplication unit, 39 ... multiplication unit

Claims (12)

A synchronization processing unit for generating image data having a plurality of colors per pixel based on image data obtained by an image pickup apparatus having an image pickup element in which a plurality of color filters are arranged;
A granular pattern addition unit for adding a predetermined granular pattern to the image data generated by the synchronization processing unit;
An image processing apparatus comprising: A first gradation conversion unit that performs a first gradation conversion process on the image data generated by the synchronization processing unit;
The image processing apparatus according to claim 1, wherein the granular pattern adding unit adds the predetermined granular pattern to the image data on which the first gradation conversion processing has been performed.   3. The image processing apparatus according to claim 2, further comprising a second gradation conversion unit that performs a second gradation conversion process different from the first gradation conversion process on the image data to which the granular pattern is added. An image processing apparatus according to 1.   The image processing apparatus according to claim 3, wherein the second gradation conversion unit performs gradation conversion processing for enhancing contrast of image data as the second gradation conversion processing.   The image processing apparatus according to claim 1, further comprising an edge extraction unit that extracts an edge used in edge enhancement processing from image data before the predetermined granular pattern is added.   The image processing apparatus according to claim 1, further comprising an intensity adjusting unit that adjusts the intensity of the predetermined granular pattern added to the image data.   The image processing apparatus according to claim 6, wherein the intensity adjustment unit adjusts the intensity of the predetermined granular pattern according to imaging sensitivity at the time of imaging by the imaging apparatus. A setting unit for setting the intensity of the predetermined granular pattern to be added to the image data;
The image processing apparatus according to claim 6, wherein the intensity adjustment unit adjusts the intensity of the predetermined granular pattern based on an operation of the setting unit by a user. A granular pattern addition unit for adding a predetermined granular pattern to image data subjected to predetermined image processing including at least a first gradation conversion process;
A second gradation conversion unit that performs a second gradation conversion process different from the first gradation conversion process on the image data to which the granular pattern is added;
An image processing apparatus comprising:   The image processing apparatus according to claim 9, wherein the second gradation conversion unit performs gradation conversion processing for enhancing contrast of image data as the second gradation conversion processing. Generating image data having a plurality of colors per pixel based on image data obtained by an image pickup apparatus having an image pickup element in which a plurality of color filters are arranged;
Adding a predetermined granular pattern to the generated image data;
An image processing method comprising: Generating image data having a plurality of colors per pixel based on image data obtained by an image pickup apparatus having an image pickup element in which a plurality of color filters are arranged;
Adding a predetermined granular pattern to the generated image data;
An image processing program for causing a computer to execute.

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