JP2003346143A - Image processing method and image processing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing method capable of holding resolution feeling while reducing false color when a reduced image of an original image (RAW image) not subjected to a signal processing such as synchronization is produced, and an image processing program for realizing the method. <P>SOLUTION: Colors are separated from the original image (CCDRAW image) obtained from a single plate color imaging device (#1), and low-pass filters (hereafter referred to as Pre-LPF) set for each color are applied to R, G, and B signals (#2). The two-dimensional zone characteristics of the Pre-LPF are similar to the two-dimensional reproducing zones of the colors specified by a color filter arrangement and a sampling theorem. The single plate image is regenerated by using the R, G, and B signals after the Pre-LPF processing (#3), and pixels are omitted from the re-arranged image to generate the reduced RAW image (#4). Signal processings (developing processings) such as gamma conversion and synchronization are applied to the reduced RAW image (#5) to provide a final reduced image. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and an image processing program, and more particularly to an image processing technique suitable for reduction processing of an original image obtained from a single-plate color image pickup apparatus.

[0002]

2. Description of the Related Art A general digital camera converts an image signal obtained from an image sensor such as a CCD into 10-bit or 12-bit digital data, performs various image processing, and then compresses such as JPEG encoding. The image data is compressed and recorded on a recording medium according to a method. Since this type of digital camera performs irreversible compression during image recording, a sufficiently good image quality may not always be obtained during reproduction or printing. The recorded image is
Since various image processing has already been performed, the image quality may be deteriorated when the user himself / herself performs further image processing on the reproduced image.

On the other hand, digital data is processed in a raw state (RAW) without image processing after image processing is not performed in the camera, and analog signals for each pixel output from the image sensor are A / D converted. There has been proposed a method for recording the image as it is. In other words, by recording raw RAW data on the camera side and performing image reproduction (development) processing with an external device such as a personal computer, high-quality printing and more advanced image editing that matches the user's purpose Is realized.

[0004]

However, RAW format data has a larger file size than JPEG format data and takes a long time for reproduction processing. Playback of RAW data is a synchronized process that obtains R / G / B information for each pixel while taking gamma conversion and white balance based on large-size original image data with only one color information for each pixel. To obtain the final reproduced image. In order to check the reproducibility of details in the screen, it is necessary to handle such a large image. For example, when only checking the reproducibility of color (check the color tone and color feeling). If you want to check the results when you change the brightness level or gamma level,
Even without using such a large image, a small image can be sufficiently confirmed. In such a case, the processing time can be greatly shortened by reducing the RAW image and performing the reproduction process.

As described above, RAW image reduction processing may be performed in order to display the processing result of RAW data at high speed or to minimize the size of the preview image file.

In Japanese Patent Laid-Open No. 2001-86345, an original image is reduced (that is, a low-frequency component is extracted), advanced color conversion is performed on the reduced image, and the original signal is superimposed on the enlarged signal. A method for improving the image quality is proposed. However, according to the conventional method disclosed in the publication, each pixel constituting the original image is RG.
The target is information having all the color information of B (or CMY).

Therefore, when the method disclosed in the publication is applied to a mosaic RAW image obtained from a single-plate color image pickup device as it is, a false color appears depending on the color, or the resolution is deteriorated. Reduction that makes full use of imaging features
There is a disadvantage that RAW images cannot be obtained.

The present invention has been made in view of such circumstances, and realizes an image processing method capable of maintaining a sense of resolution while reducing false colors when an original image is reduced. An object is to provide an image processing program.

[0009]

In order to achieve the above object, the present invention is an image processing method for generating a reduced image from a digital image signal of an original image composed of pixels of a plurality of colors having different periodicity of color arrangement. A filter processing step of applying a low-pass filter having a two-dimensional band characteristic similar to the two-dimensional reproduction band of each color defined by the color arrangement and the sampling theorem for each color signal of the original image, and the filter processing step A reduction processing step for generating a reduced original image by thinning out pixels from the image generated through the above process, and reduction of the original image by performing image reproduction signal processing on the reduced original image generated by the reduction processing And a reproduction processing step for obtaining an image.

According to the present invention, when generating a reduced image of an original image (RAW image) that has not been subjected to signal processing such as synchronization, the reproduction band of each color signal (original signal) of the original image can be destroyed. The low-pass filter having a band characteristic similar to the two-dimensional reproduction band of each color is applied so that the number of pixels is reduced from the image after the low-pass filter process to obtain a reduced original image. Note that the pixel thinning amount is set depending on the reduction ratio of the reduced image to be finally generated. The reduced original image obtained in this way reflects the characteristics of the reproduction characteristics of the original image before reduction.

The reduced original image is subjected to image reproduction processing such as gamma conversion, white balance adjustment, and synchronization to obtain a final reduced image. As a result, the reproduction processing time can be shortened, and the maximum resolution of each color signal can be maintained while preventing the occurrence of false colors in the final image.

Another aspect of the present invention provides a program for realizing the above-described method invention by a computer. In other words, the image processing program according to the present invention is a program for causing a computer to realize an image processing function for generating a reduced image from a digital image signal of an original image composed of pixels of a plurality of colors having different periodicity of color arrangement. A filter processing function that applies a low-pass filter having a two-dimensional band characteristic similar to the two-dimensional reproduction band of each color defined by the color arrangement and the sampling theorem for each color signal of the original image, and generated through the filter processing function A reduction processing function for generating a reduced original image by thinning out pixels from the generated image, and performing a signal processing for image reproduction on the reduced original image generated by the reduction processing, thereby reducing the reduced image of the original image The reproduction processing function to be obtained is realized in a computer.

The image processing program of the present invention may be configured as a single application software, or may be incorporated as part of an application such as image processing software or file management software.
Further, the image processing program of the present invention is not limited to being applied to a computer system such as a personal computer, and may be applied as an operation program for a central processing unit (CPU) incorporated in an information device such as a digital camera or a mobile phone. Is possible.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an image processing method and an image processing program according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of an image pickup apparatus for recording an original image to which an image processing method according to an embodiment of the present invention is applied. The imaging device 10 is a single-plate digital camera that converts an optical image of a subject imaged via the imaging unit 12 into digital image data and records it on a memory card 14.
The imaging unit 12 includes an optical lens 16, an optical low-pass filter (OLPF) 17, a color filter 18, and the imaging device 2.
Contains zero.

The image sensor 20 is a CCD type or CMOS.
This is an image sensor represented by a mold. Image sensor 2
A large number of photodiodes (photosensitive pixels) are two-dimensionally arranged on the 0 light receiving surface, and subject information passing through the optical lens 16 is photoelectrically converted. Optical low-pass filter 17
Has an effect of removing high frequency components equal to or higher than the sampling frequency depending on the pixel pitch of the image sensor 20, and prevents aliasing in the final image after image reproduction (signal processing).

The color filter 18 has a predetermined color arrangement such that any one of R, G, and B is present at a position corresponding to one pixel of the image sensor 20, and is incident on a photodiode as a light receiving element. Select the light color.

FIG. 2 shows an example of a primary color filter array. In the honeycomb arrangement shown in FIG. 2A, the centers of the geometric shapes of the light receiving elements (photodiodes) are arranged so as to be shifted by 1/2 pitch in the row direction and the column direction. In the Bayer arrangement shown in FIG. 2B, the light receiving elements are arranged in a square matrix at a constant pitch in the row direction and the column direction. Note that the structure of the pixel array shown in FIG. 2 is periodically repeated in the horizontal direction and the vertical direction on the imaging plane of the actual image sensor 20. Of course, in the practice of the present invention, the arrangement structure of the color filters 18 is not limited to the example shown in FIG. 2, and various arrangement structures such as G stripes are possible. In this example, primary color filters are used. However, the present invention is not limited to primary color filters, and yellow (Y), magenta (M), cyan (C),
It is also possible to use a complementary color filter made of green (G).

The light that has passed through the optical lens 16 in FIG. 1 passes through the optical low-pass filter 17 and the color filter 18 and enters the image sensor 20. The subject image formed on the light receiving surface of the image sensor 20 is converted into a signal charge of an amount corresponding to the amount of incident light by each photodiode, and a voltage corresponding to the signal charge based on a pulse supplied from a driver circuit (not shown). It is sequentially read out as a signal (image signal).

The image pickup device 20 has an electronic shutter function for controlling the charge accumulation time (shutter speed) of each photodiode according to the timing of the shutter gate pulse. The operation (exposure, reading, etc.) of the image sensor 20 is controlled by the CPU 22.

The image signal output from the image sensor 20 is sent to the analog processing unit 24, where the analog processing unit 24 performs processing such as analog gain and CDS (correlated double sampling). The signal generated by the analog processing unit 24 is converted into a digital signal by the A / D conversion unit 26.

The A / D converted image data is recorded in the memory card 14 through necessary signal processing according to the operation mode of the image pickup apparatus 10 or by omitting signal processing. The image pickup apparatus 10 of this example can record an image in JPEG format and also can display an image immediately after A / D conversion (hereinafter, CCDRAW).
It is called an image. ) Can be recorded.

When recording in the JPEG format, the A / D converted image data is sent to the signal processing unit 28. The signal processing unit 28 performs synchronization (processing for calculating the color of each point by interpolating the spatial shift of the color signal associated with the color filter array), white balance (WB) adjustment, gamma correction, luminance / color difference signal generation. , Zooming (enlargement /
Image processing means for performing various processing such as reduction processing and pixel number conversion (resizing) processing, and processes image signals in accordance with commands from the CPU 22. Signal processor 28
Includes an image memory 30 that can temporarily store an image being processed, and performs image signal processing while using the image memory 30.

The image data that has undergone predetermined signal processing in the signal processing unit 28 is sent to the compression / decompression unit 32 and compressed according to the JPEG compression format. The compression format is not limited to JPEG, MPEG or other methods may be adopted, and a compression engine corresponding to the compression format used is used.

The compressed image data is recorded on the memory card 14 via the card interface unit 34. The means for storing the image data is not limited to the semiconductor memory represented by the memory card 14, but a magnetic disk,
Various media such as an optical disk and a magneto-optical disk can be used. In addition, not only removable media,
A recording medium (internal memory) built in the imaging apparatus 10 may be used.

On the other hand, in the mode for recording a CCDRAW image, the image data digitized by the A / D converter 26 is recorded on the memory card 14 via the CPU 22 without being subjected to synchronization or other signal processing. . That is, CCDR
The AW image is an image that has not undergone signal processing such as gamma conversion, white balance adjustment, and synchronization, and holds only one piece of color information that differs for each pixel corresponding to the array pattern of the color filter 18. It is a mosaic image. Of course, since the compression process is not performed, it has a large file size. When a CCDRAW image is recorded on the memory card 14, it may be recorded with reversible compression or uncompressed data may be recorded.

The CPU 22 is a control unit that performs overall control of the camera system in accordance with a predetermined program, and controls the operation of each circuit in the image pickup apparatus 10 based on an instruction signal from the operation panel 36. The ROM 38 stores programs executed by the CPU 22 and various data necessary for control. The RAM 40 is used as a work area for the CPU 22.

The operation panel 36 is a means for a user to input various instructions to the image pickup apparatus 10. For example, a mode selection switch for selecting an operation mode of the image pickup apparatus 10 and a menu item selection operation ( Cursor movement operation), four-way key to input instructions such as frame advance / rewind of playback image, execution key to instruct selection (registration) and execution of operation, selection item to delete desired instruction Various operation means such as a cancel key for canceling, a power switch, a zoom switch, and a release switch are included.

The CPU 22 controls the image pickup section 12 such as the image pickup device 20 in accordance with various shooting conditions (exposure conditions, presence / absence of strobe light emission, shooting mode, etc.) in accordance with an instruction signal input from the operation panel 36, and automatic exposure. (AE)
Control, auto focus adjustment (AF) control, auto white balance (AWB) control, lens drive control, image processing control,
Read / write control of the memory card 14 is performed.

For example, when the CPU 22 detects a half-press of the release switch (S1 = ON) and performs an automatic focus adjustment (AF) control, the CPU 22 fully presses the release switch (S2).
= ON) is detected, exposure and readout control for capturing a recording image is started. Further, the CPU 22 sends a command to a strobe control circuit (not shown) as necessary to control light emission of a flash light emitting tube (light emitting unit) such as a xenon tube.

The signal processing unit 28 includes an auto calculation unit for performing calculations necessary for AE and AF control, and a focus evaluation value based on an image signal taken in response to half-pressing of the release switch (S1 = ON). Calculation, AE calculation, etc. are performed, and the calculation result is transmitted to the CPU 22. When the release switch is fully pressed (S2 = ON), the CPU 22 controls a lens driving motor (not shown) based on the result of the focus evaluation value calculation, and moves the optical lens 16 to the in-focus position. Exposure is controlled by controlling the aperture and electronic shutter. Thus, the captured image data is recorded on the memory card 14 according to the recording mode.

Next, the image pickup apparatus 10 configured as described above.
An image processing apparatus that handles a CCDRAW image recorded by, and an image processing method thereof will be described.

The CCDRAW image recorded by the image pickup apparatus 10 is reproduced (developed) by a personal computer or a dedicated image processing apparatus. FIG. 3 is a block diagram showing a hardware configuration example of the personal computer 50 in which the image processing program according to the embodiment of the present invention is incorporated.

As shown in the figure, a personal computer 50 is necessary for the operation of the CPU 52, which functions as a control unit and an arithmetic unit, a RAM 54 used as a temporary storage area for data and a work area when the CPU 52 executes a program, and the CPU 52. Rewritable nonvolatile memory (RO) that stores various programs, various setting values, network connection information, etc.
M) 56, a hard disk device 58 in which an operating system (OS) of the personal computer 50, an image processing program according to the embodiment of the present invention, various application software, an image file recorded by the user, and the like are stored.
A calendar clock 60 for engraving the date and time, a media control unit 64 for performing read / write control of an external recording device 62 represented by a memory card or a magneto-optical disk, an input device 66 such as a keyboard or a mouse, and an input device 66 An input control unit 68 that controls signal input, a display 70 that displays images, characters, and the like, a display control unit 72 that outputs a display signal to the display 70, and a USB or wireless LAN
A communication device 74 for connecting to an external device or a communication network in accordance with a predetermined communication method, and a bus 76 for connecting the above components.

The personal computer 50 having the above-described configuration is
Since it is well known except for the image processing program to which the present invention is applied, detailed description of each component will be omitted.

Next, an image processing program for causing the personal computer 50 to function as an image processing apparatus will be described. The image processing program stores an image file stored in the hard disk device 58 or the external recording device 62 or an image file stored in an external device (for example, the imaging device 10) connected via the communication device 74. The personal computer 50 is operated so that it can be browsed and processed (edited).

FIG. 4 is a processing block diagram showing an image processing procedure for generating a reduced image from a CCDRAW image. According to the figure, the CCDRAW image, which is a single-plate original image (one side), is color-separated (# 1), and each color signal image of R, G, B (three sides)
Divide into A low pass filter (hereinafter referred to as Pre-LPF) set for each color is applied to the color-coded R signal, G signal, and B signal (# 2). As will be described in detail later, Pre-LPF having a band characteristic similar to each two-dimensional reproduction band is applied to each color signal subjected to color separation.

Using the R, G, and B signals obtained by applying Pre-LPF, rearrangement into a CCDRAW type pixel array (# 3) is performed to regenerate a single-plate image.

Subsequently, a process of thinning out the pixels of the regenerated CCDRAW type image at a certain rate is performed (# 4) to reduce the image. A CCDRAW type reduced image (hereinafter referred to as a reduced RAW image) generated by the thinning process is input to the development processing unit for signal processing (# 5), where gamma conversion,
Final image after processing such as white balance adjustment and synchronization (for example, RGB data which is a reduced image for display)
Convert to

Note that when reproducing a CCDRAW image without reducing it, the above processing steps (# 1) to (# 4) are omitted,
A CCDRAW image is directly input to the signal processing step (# 5) to obtain a reproduced image.

FIG. 5 shows an example of processing the honeycomb array image in accordance with the image processing process shown in FIG. FIG. 5 shows a processing process for generating a reduced image from a CCDRAW image having a honeycomb array. This processing process is used, for example, for preview display of the CCDRAW processing result.

As shown in FIG. 5A, the original image CC
The DRAW image is a mosaic image reflecting the pixel arrangement of the honeycomb arrangement. The image information of the original image is color-separated and divided into three surfaces R, G, and B as shown in FIG. At this time, the pixels are rearranged while filling the missing pixel points (blank positions) at a constant rate. Although the phase is changed by filling the blank pixel points, the periodic arrangement of the pixels is maintained.

The color-separated R signal, G signal, B
The signal is subjected to a Pre-LPF designed to preserve the characteristics of each two-dimensional reproduction band. In the case of the honeycomb arrangement, the Pre-LPF applied to the R signal and the B signal drops the diagonal band, and the Pre-LPF applied to G holds the diagonal band. In this way, a three-surface image shown in FIG.

A process (CCDRAW file conversion process) is performed to return the three-sided image after the pre-LPF processing to the original one-sided image (the same mosaic image as the CCDRAW image), as shown in FIG. Recreates a mosaic-like image.

A thinning process is performed from the rearranged mosaic image to generate a reduced RAW image shown in FIG. In the figure, an example of reduction to 1/3 is shown. FIG.
The R and G pixels indicated by “shaded” in (d) correspond to the R and G pixels “shaded” in FIG. 5E, respectively.

Based on the reduced RAW image obtained in this way, processing such as gamma conversion, white balance adjustment, and synchronization is performed, and the final reduced image shown in FIG. 5F (for example, RGB which is a reduced image for display). Data). As a result, the reduced image can be displayed at high speed.

Next, the details of the Pre-LPF process will be described.

As described above, it is important to design the Pre-LPF according to the reduction ratio when considering reducing the CCDRAW image and performing predetermined processing on the reduced RAW image. The band characteristic of this Pre-LPF may be a reduction ratio × fs / 2 (where fs is a sampling frequency). However, if this is applied uniformly regardless of the color, a color signal having a high sampling frequency ( Deterioration occurs in terms of resolution for the G signal in the honeycomb array or Bayer array, and deterioration occurs in the point of a false signal for the color signal originally having a low sampling frequency (R and B signals in the honeycomb array or Bayer array). End up.

Therefore, in the embodiment of the present invention, a pre-LPF set for each color is applied to the CCDRAW image,
The pre-LPF band characteristics to be applied to each color signal are the reduction rate x f
s / 2, and the two-dimensional characteristic is similar to the reproduction band of each original color.

FIG. 6 is a diagram showing the reproduction band of each color based on the sampling theorem on the spatial frequency coordinates (absolute spatial frequency coordinate system that is not standardized) for each of the honeycomb array and the Bayer array. is there. FIG.
As shown in (a), in the case of the honeycomb arrangement, the reproduction bands of the R and B signals have a rhombus shape with a reproduction band in the oblique 45-degree direction being lower than in the horizontal and vertical directions. In other words, although the reproducibility (resolution) is high for the input of the vertical line and the horizontal line, the diagonal 4
The reproducibility is low (1/2 ^1/2 times) for an input of a line in the 5 degree direction (hereinafter referred to as a diagonal line).

On the other hand, in the case of the G signal in the honeycomb arrangement, the horizontal and vertical directions have a reproduction band equivalent to that of the R and B signals, and the oblique 45 degree direction is twice that of the R and B signals. Has a reproduction band. That is, the two-dimensional reproduction band of the G signal has a rectangular (square) shape as shown in FIG.

Such a difference in reproduction band is caused by the arrangement period (pixel arrangement structure) of the color filter 18 (see FIG. 2). In the case of the honeycomb arrangement, the spatial sampling frequencies of R and B are equal to the spatial sampling frequency of G in the horizontal and vertical directions, but the spatial sampling frequency of R and B is half that of G in the oblique 45 degree direction. . The CCDRAW image reflects the arrangement structure of the color filters and has different band characteristics for each color.

FIG. 6B shows a two-dimensional reproduction band of each color in the Bayer array. For the Bayer layout,
The two-dimensional reproduction band of the R and B signals is rectangular, and the two-dimensional reproduction band of the G signal is diamond.

As is apparent from FIGS. 6 (a) and 6 (b), R,
The reproduction bands of the B signal and the G signal are in a relationship rotated by 45 degrees. The difference in size is due to the number of sampling points of the G signal.

In the embodiment of the present invention, the CCDR shown in FIG.
In consideration of the reproduction characteristics for each color in the AW image, the band characteristics of the Pre-LPF to be applied to each color signal in the image processing process described with reference to FIGS. 4 and 5 are similar to the reproduction bands of each original color.

Specifically, in the image processing process of FIG. 5, the R- and B-signals are pre-shown in FIG.
LPF is applied, and Pre-LPF shown in FIG. 8 is applied to the G signal. In the Pre-LPF shown in FIG. 7, when the jth filter coefficient is a _j and the input R signal is R _j (before processing), the Pre-LPF
R signal value Ri at post-processing pixel position i (after processing)
Is expressed by the following equation.

[0057]

R _i (after processing) = Σa _j R _j (before processing) / 16384 (1) The same calculation is performed for the B signal. For the G signal, the same calculation is performed using the filter coefficients shown in FIG.

The Pre-LPF for the R and B signals shown in FIG.
The pre-LPF for the G signal shown in FIG. 8 has a coefficient arrangement that increases the reproduction band in the oblique direction rather than the vertical and horizontal directions.

As described in FIG. 6, the R and B signals and the G
Since the signal reproduction bands are in a relationship of being rotated by 45 degrees with each other, the Pre-LPF applied to these may have their filter coefficients rotated by 45 degrees with respect to each other.

Actually, the Pre-LPF shown in FIG. 7 is obtained by rotating the coefficient arrangement of the Pre-LPF shown in FIG. 8 by 45 degrees. In this way, by applying the G-signal with the Pre-LPF filter coefficient rotated by 45 degrees applied to the R and B signals, it is possible to resemble the reproduction band of the honeycomb array primary color filter.

When a reduced image is generated from a CCDRAW image acquired by an imaging device using a Bayer array primary color filter, the Pre-LPF in FIG. 7 is applied to the G signal, and the Pre-LPF in FIG. , B signal. That is, in the case of the Bayer array, the Pre-LPF applied to the G signal drops the diagonal band, and the Pre-LPF applied to the R and B signals holds the diagonal band.

By using such Pre-LPF,
It is possible to minimize the occurrence of false colors after image reproduction without sacrificing the sampling frequency of each color.

7 and 8 exemplify an 11 × 11 pixel matrix filter, the form of the filter is not limited to this, and can be appropriately designed in consideration of the color arrangement.
When the pixel array of the input CCDRAW image is fixed (CC
If the standard for DRAW data is determined), the filter configuration can be fixed. When it is assumed that CCDRAW images of multiple types of pixel array patterns are handled (when configured as general-purpose software that supports processing of various types of CCDRAW data), the filter configuration (filter coefficient) depends on the color array information. ) Is preferably variably set.

In order to make the software of general-purpose type, the filter form is variably set by recognizing the information of the pixel arrangement.
For example, pre-LPF that automatically adds color filter information of the image sensor to a CCDRAW image file, reads the color filter information during image processing, and maintains the characteristics of the reproduction characteristics of the color arrangement automatically. Set.

According to the embodiment of the present invention described above, the reduction having the characteristics of the same reproduction band from a large-size CCDRAW image.
A CCDRAW image can be generated, and image reproduction processing (gamma conversion, white balance adjustment,
Since the final reduced image is obtained by performing processing such as synchronization, it is possible to prevent generation of false colors in the final image and to maintain the maximum resolution of each color signal.

The embodiment of the present invention is extremely effective in displaying the processing result at high speed when editing an image on an image processing application. According to the present invention, it is possible to display a result of image editing such as a change in color tone or a change in brightness at high speed. In other words, a reduced RAW image that retains the characteristics of the reproduction characteristics of the original image is generated, and signal processing is performed on the reduced RAW image based on editing instructions such as changing the tone, so that the processing result can be displayed in a short time. .

FIG. 9 shows an example of an application screen.
As shown in the figure, a preview display unit 82 is formed that displays a reduced image (reduced version final image) as a processing result beside an input window 80 for specifying editing parameters. When the user changes the editing parameters, the reduced image signal processing is performed in accordance with the input, and the processing result is displayed on the preview display unit 82. The user appropriately adjusts the editing parameters while confirming the reduced image on the preview display unit 82,
Determine the parameters. After determining the parameters, reproduction processing is performed on the large-size original image to obtain a final image.
Compared with the case of handling a large original image at the parameter adjustment stage (image editing stage), the processing time can be greatly reduced.

The means for carrying out the present invention is not limited to a personal computer, but may be a dedicated image processing apparatus (image reproducing apparatus or image processing apparatus). Further, the image processing is not limited to a mode realized by software, and part or all of the processing may be realized by dedicated hardware (signal processing circuit).

Further, a computer program for realizing the above-described image display function is recorded on a CD-ROM, a magnetic disk or other recording medium, and the program is provided to a third party through the recording medium, or communication such as the Internet. It is also possible to provide a download service for the program through a line.

Further, in the above-described embodiment, the color separation step is provided before the above-mentioned Pre-LPF is applied to the CCDRAW image (# 1 in FIG. 4). Not necessarily required. For example, if the Pre-LPF is modified in consideration of the CCDRAW image format, the color separation step (# 1 in FIG. 4) and the rearrangement step (# 3 in FIG. 4) can be omitted.

[0071]

As described above, according to the present invention, when a reduced original image is obtained from an unprocessed original image that has not undergone signal processing such as synchronization, it is similar to the two-dimensional reproduction band of the original signal. Since a low-pass filter having a two-dimensional band characteristic is applied, the characteristics of the reproduction band of the current signal can be maintained, and the occurrence of false colors in the final image generated from the reduced original image can be prevented. The maximum resolution of the signal can be maintained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an imaging apparatus that records an original image to which an image processing method according to an embodiment of the present invention is applied.

FIG. 2 is a schematic diagram illustrating an example of a primary color type color filter array;

FIG. 3 is a block diagram showing a hardware configuration example of a personal computer in which an image processing program according to an embodiment of the present invention is incorporated.

FIG. 4 is a processing block diagram showing an image processing procedure for generating a reduced image from a CCDRAW image.

FIG. 5 is an explanatory diagram showing an example of processing an image of a honeycomb array in accordance with the image processing process shown in FIG.

FIG. 6 is a diagram showing the reproduction band of each color on the spatial frequency coordinate based on the sampling theorem for each of the honeycomb array and the Bayer array.

7 is a diagram showing an image processing process shown in FIG.
Diagram showing an example of Pre-LPF applied to the B signal

8 is a diagram showing an example of a Pre-LPF applied to a G signal in the image processing process shown in FIG.

FIG. 9 is a diagram showing an example of an application screen to which the image processing program according to the embodiment of the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Imaging device, 12 ... Imaging part, 14 ... Memory card,
18 ... color filter, 20 ... image sensor, 22 ... CP
U, 50 ... PC, 52 ... CPU, 54 ... RAM, 5
8. Hard disk device

──────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme code (reference) H04N 9/07 H04N 1/40 D 5C079 9/79 1/46 Z // H04N 101: 00 9/79 G F-term (reference) 5B057 BA02 BA12 CA01 CA08 CA12 CA16 CB01 CB08 CB12 CB16 CC01 CD07 CE06 CE17 CG01 CH07 CH08 CH11 5C055 AA06 BA06 CA16 EA05 5C065 AA03 BB48 EE05 EE06 GG05 5C076 AA22 BB03 PP RR21 SS03 TT09 5C079 HB01 JA14 JA16 JA23 LA12 LA14 LA23 LA31 LB01 MA02 MA04 MA11 MA17 NA11

Claims (3)

[Claims] 1. An image processing method for generating a reduced image from a digital image signal of an original image composed of pixels of a plurality of colors having different periodicity of the color arrangement, wherein the color arrangement and the sampling theorem for each color signal of the original image A filter processing step of applying a low-pass filter having a two-dimensional band characteristic similar to the two-dimensional reproduction band of each color defined from the above, and generating a reduced original image by thinning out pixels from the image generated through the filter processing step A reduction processing step, and a reproduction processing step of obtaining a reduced image of the original image by performing image reproduction signal processing on the reduced original image generated by the reduction processing. Image processing method. 2. A program for causing a computer to realize an image processing function for generating a reduced image from a digital image signal of an original image composed of pixels of a plurality of colors with different periodicity of color arrangement, each color of the original image A filter processing function that applies a low-pass filter having a two-dimensional band characteristic similar to the two-dimensional reproduction band of each color defined by the color arrangement and the sampling theorem for the signal, and a pixel from an image generated through the filter processing function A reduction processing function for generating a reduced original image by thinning, a reproduction processing function for obtaining a reduced image of the original image by performing image reproduction signal processing on the reduced original image generated by the reduction processing; An image processing program for causing a computer to realize the above. 3. The original image includes R (red), G (green), and B
It is an image acquired using a single-plate color imaging device equipped with a (blue) primary color filter, and is a digital image that is not subjected to signal processing such as gamma conversion, white balance adjustment, and synchronization The image processing program according to claim 2.