JP4879508B2 - Conversion parameter calculation method, conversion parameter calculation program, and image processing apparatus - Google Patents

Description

  The present invention relates to a conversion parameter calculation method, a conversion parameter calculation program, and an image processing apparatus, and more particularly to a technique for acquiring a device-independent color system image from three primary color images captured in frame sequential order.

  In general, a 3 × 3 matrix or a 3D-LUT (three-dimensional lookup table) is used to convert a color image obtained through a color filter of three primary colors into an XYZ image of the XYZ color system (patent) References 1 and 2).

However, since the color image values of the three primary colors obtained as described above include the influence of flare, there is a problem that the accuracy when converting the color image of the three primary colors into an XYZ image is lowered. It was. In order to solve such a problem, Patent Literature 3 discloses a flare correction method in which flare characteristics of a camera are measured in advance and all captured images are corrected using the flare characteristics.
JP 2001-94800 A JP-A-9-37091 JP 2003-69896 A

  By the way, the flare characteristic also changes depending on the aperture and focal length at the time of imaging. However, it is difficult to measure flare characteristics in advance for each aperture and focal length of the camera. For this reason, in the flare correction method disclosed in the above-mentioned Patent Document 3, flare correction cannot be sufficiently performed, and the accuracy in converting a color image of three primary colors into an XYZ image is reduced, and color reproducibility is reduced. There was a risk of lowering.

  The present invention has been made in view of such circumstances. A conversion parameter calculation method and a conversion parameter calculation capable of accurately correcting flare during imaging and obtaining a colorimetric color reproduction image with high color reproducibility. It is an object to provide a program and an image processing apparatus.

To achieve the above object, a conversion parameter calculation method according to the first aspect of the present invention is a conversion parameter calculation method for calculating a conversion parameter for obtaining a colorimetric color reproduction image from at least three primary color images. In (a) acquiring a color image of at least three primary colors obtained by imaging a scene for which colorimetric color reproduction is desired, and (b) assuming the flare amount generated at the time of acquiring the color image. Calculating a conversion parameter for converting the color image value of the scene into the colorimetric value based on the flare amount, the color image value of the scene, and the colorimetric value measured for the scene; (C) a colorimetric value calculation step of calculating a colorimetric value of the scene based on the color image value of the scene and the calculated conversion parameter; (d) a colorimetric value measured for the scene; A step of calculating an average value of color differences based on the colorimetric values calculated in the step (c), and (e) repeating the steps (b) to (d) while changing the assumed flare amount. A flare amount calculating step for obtaining a flare amount that minimizes the average value of the color differences, and (f) a step of acquiring a conversion parameter based on the flare amount that minimizes the average value of the color differences.

According to the conversion parameter calculation method according to the first aspect , by calculating the flare amount for each captured image, it is possible to accurately correct the flare during imaging. By using such conversion parameters, a colorimetric color reproduction image with high color reproducibility can be acquired.

The conversion parameter calculation method according to a second aspect of the present invention is characterized in that, in the first aspect , the flare amount in which the weighted average value of the color difference is minimized is obtained in the flare amount calculation step (e). To do.

According to the conversion parameter calculation method according to the second aspect , for example, by increasing the weight applied to a specific color, the accuracy of the colorimetric value of the color is increased when a colorimetric color reproduction image is acquired. be able to.

In the conversion parameter calculation method according to the third aspect of the present invention, in the first or second aspect , the colorimetric color reproduction image is an XYZ color system XYZ image or a Lab color system Lab image. It is characterized by being. In the third aspect , the three primary color images and the colorimetric color reproduction image are limited.

A conversion parameter calculation program according to a fourth aspect of the present invention is a conversion parameter calculation program for calculating a conversion parameter for obtaining a colorimetric color reproduction image from at least three primary color images. Assuming a function of acquiring a color image of at least three primary colors obtained by imaging a scene to be realized, a flare amount generated when acquiring the color image, the assumed flare amount, a color image value of the scene, and A function for calculating a conversion parameter for converting the color image value of the scene into the colorimetric value based on the colorimetric value measured for the scene, and the color image value of the scene and the calculated conversion parameter. Based on the function for calculating the colorimetric value of the scene, the colorimetric value measured for the scene, and the calculated colorimetric value, the average value of the color difference is calculated. A function of repeatedly calculating the average value of the color difference while changing the assumed flare amount, and obtaining a flare amount that minimizes the average value of the color difference, and the average value of the color difference is minimized. The computer is realized with a function of acquiring a conversion parameter based on a flare amount.

By applying software and firmware including the conversion parameter calculation program according to the fourth aspect to a device having an image playback function such as a personal computer (PC), a video playback device (video deck, television), a digital camera, etc. The image processing method and the image processing system of the invention can be realized.

An image processing apparatus according to a fifth aspect of the present invention includes an image acquisition unit that acquires a color image of at least three primary colors obtained by imaging a scene for which colorimetric color reproduction is desired, and a flare amount generated when the color image is acquired To convert the color image value of the scene into the colorimetric value for each of the assumed flare amounts based on the color image value of the scene and the colorimetric value measured for the scene. Conversion parameter calculation means for calculating a conversion parameter of the scene, and colorimetric value calculation means for calculating a colorimetric value for calculating the colorimetric value of the scene based on the color image value of the scene and the calculated conversion parameter Color difference average value calculating means for calculating an average value of color differences based on the colorimetric values measured for the scene and the calculated colorimetric values; and color difference values calculated for each of the assumed flare amounts. Average value The flare amount calculating means for obtaining the flare amount that minimizes the average value of the color difference, the conversion parameter acquiring means for acquiring the conversion parameter based on the flare amount that minimizes the average value of the color difference, and the image acquiring means And a colorimetric color reproduction means for obtaining a colorimetric color reproduction image based on the acquired conversion parameter when an image of at least three primary colors is input via

According to the image processing apparatus of the fifth aspect , by calculating the flare amount for each captured image, it is possible to accurately correct the flare at the time of imaging, and colorimetric color reproduction with high color reproducibility. Images can be acquired.

  According to the present invention, by calculating the flare amount for each captured image, it is possible to accurately correct the flare during imaging. Thereby, a colorimetric color reproduction image with high color reproducibility can be acquired. Also, by increasing the weight applied to a specific color when calculating the flare amount, the accuracy of the colorimetric value of that color can be increased.

  Hereinafter, preferred embodiments of a conversion parameter calculation method, a conversion parameter calculation program, and an image processing apparatus according to the present invention will be described with reference to the accompanying drawings. The image processing system described below includes a frame sequential imaging device 10 and an image processing device 300. When linear conversion is performed to a CIE (International Commission on Illumination) color matching function, the color image of the three primary colors captured through a color filter designed to have a spectral sensitivity so as to reduce errors is obtained by the image processing apparatus 300 as a colorimetric color. It is converted into a reproduced image (for example, an XYZ image or a Lab image).

  FIG. 1 is a block diagram showing a field sequential imaging apparatus constituting an image processing system according to an embodiment of the present invention. A field sequential imaging device 10 shown in FIG. 1 includes an imaging device main body 100 and a rotating color filter device 200. The frame sequential imaging device 10 records a frame sequential color image captured through the rotating color filter device 200 on a memory card 154, and the overall operation of the device is controlled by a central processing unit (CPU) 140. The The ROM 151 stores programs, adjustment values, and the like in advance, and these programs, adjustment values, and the like are read as appropriate.

  The imaging apparatus main body 100 is provided with an operation unit 138 including a shutter button and a mode dial for setting an imaging mode, a playback mode, and the like. A signal corresponding to an operation on the operation unit 138 is input to the CPU 140. .

  Image light indicating a subject is imaged on a light receiving surface of a black and white image sensor 116 such as a CCD image sensor or a CMOS image sensor via a rotating color filter device 200, an imaging lens 112, and a diaphragm 114.

  The turret plate 202 of the rotary color filter device 200 is rotationally driven by a filter driving unit 137 and a motor 204 controlled by the CPU 140 so that each color filter is positioned on the optical axis of the imaging lens 112 for each frame sequential imaging. Be controlled.

  The imaging lens 112 is driven by a lens driving unit 136 controlled by the CPU 140 to perform focus control and the like. The diaphragm 114 is composed of, for example, five diaphragm blades, and is driven by a diaphragm driving unit 134 controlled by the CPU 140. For example, the diaphragm 114 is controlled in five stages from the diaphragm value F2.8 to F11 in increments of 1AV.

  In addition, the CPU 140 controls the diaphragm 114 via the diaphragm driving unit 134 and controls the charge accumulation time (shutter speed) in the monochrome image sensor 116 via the image sensor control unit 132.

  The signal charge accumulated in the monochrome image sensor 116 is read out as a voltage signal corresponding to the signal charge based on the readout signal applied from the image sensor control unit 132. The voltage signal read from the black and white image sensor 116 is applied to the analog signal processing unit 118, where the voltage signal for each pixel is sampled and held, amplified, and then applied to the A / D converter 120. The A / D converter 120 converts sequentially input analog signals into digital signals, and the digital signals (image data) are temporarily stored in a memory (SDRAM) 148 via the image input controller 122.

  The image data stored in the memory 148 is output to the VRAM 150 after required signal processing is performed via the digital signal processing unit 124. The VRAM 150 includes an A area and a B area each storing image data representing an image for one frame. In the VRAM 150, image data representing an image for one frame is rewritten alternately in the A area and the B area. The written image data is read from an area other than the area where the image data is rewritten out of the A area and B area of the VRAM 150. The image data read from the VRAM 150 is encoded by the video encoder 128 and output to a liquid crystal monitor (LCD) 130 provided on the back of the camera. As a result, the subject image is displayed on the display screen of the liquid crystal monitor 130.

  Further, when the shutter button of the operation unit 138 is pressed (half-pressed) in the first stage, the AE operation and the AF operation are started. That is, the image data output from the A / D converter 120 is taken into the AF detection unit 142 and the AE detection unit 144. The AF detection unit 142 uses image data (for example, a signal in the center region (focus region) of the monochrome image sensor 116), and uses a high-pass filter (HPF) to extract high-frequency components from one-dimensional horizontal continuous image data. A value (AF evaluation value) obtained by extracting and integrating the high frequency components is output to the CPU 140. The AE detection unit 144 integrates image data of the entire screen, or integrates image data with different weights at the center and peripheral portions of the screen, and outputs the integrated value to the CPU 140.

  Based on the AF evaluation value input from the AF detection unit 142, the CPU 140 moves the imaging lens 112 through the lens driving unit 136 to the lens position where the AF evaluation value is maximized, and the integration input from the AE detection unit 144. The brightness of the subject (imaging Ev value) is calculated from the value, and the aperture value of the diaphragm 114 and the electronic shutter (shutter speed) of the black and white image sensor 116 are determined based on the imaging Ev value according to a predetermined program diagram. Based on the determined aperture value, the aperture 114 is controlled via the aperture drive unit 134, and the charge accumulation time in the monochrome image sensor 116 is controlled via the image sensor control unit 132 based on the determined shutter speed.

  When the AE operation and the AF operation are completed and the shutter button is pressed in the second stage (full press), frame-sequential imaging is performed in response to the depression, and the image data for each color in the frame sequence is the image data It is temporarily stored in the memory 148 via the input controller 122.

  The CPU 140 corrects the color shift of the image data for each color stored in the memory 148.

  The digital signal processing unit 124 performs predetermined signal processing such as offset control, gain control processing including white balance correction and sensitivity correction, gamma correction processing, and YC processing on the image data for each color after color misregistration correction. Do. The YC-processed image data (YC data) is read from the digital signal processing unit 124 and stored in the memory 148 again. Subsequently, the YC data is output to the compression / decompression processing unit 126, and a predetermined compression process such as JPEG (Joint Photographic Experts Group) is executed. The compressed YC data is again output to and stored in the memory 148, read by the media controller 152, and recorded on the memory card 154.

  When RAW data recording is performed, the frame sequential RAW data input via the image input controller 122 is temporarily stored in the memory 148 and then directly stored as a RAW data file (the signal from the digital signal processing unit 124). It is recorded in the memory card 154 without being processed or compressed.

  FIG. 2 is a block diagram illustrating a hardware configuration example of an image processing apparatus constituting the image processing system according to the present invention. As shown in the figure, the image processing apparatus 300 is composed of, for example, a personal computer (PC), and stores a central processing unit (CPU) 310 that mainly controls the operation of each component and a control program for the apparatus. Or a main memory 312 serving as a work area when the program is executed, an operating system (OS) of a personal computer, an image processing program according to the present invention, various application software, a hard disk device 314 storing user images, and the like. A CD-ROM device 316 capable of reading data from the ROM, a card interface (card I / F) 317 for reading image data (RAW data) from the memory card 154, and a display memory 318 for temporarily storing display data And image data and text from the display memory 318 A monitor device 320 such as a CRT monitor or a liquid crystal monitor that displays images, characters, etc. according to data, a keyboard 322, a mouse 324 as a position input device, and a mouse pointer on the monitor device 320 by detecting the state of the mouse 324 A mouse controller 326 that outputs signals such as the position of the mouse 324 and the state of the mouse 324 to the CPU 310, a communication interface (communication I / F) 327 that communicates with the frame sequential imaging device 10 and the like, and a bus that connects the above components 328.

  The image processing apparatus 300 having the above-described configuration is well known except for the image processing program stored in the hard disk device 314, and therefore detailed description of each component will be omitted. The image processing program according to the present invention can be installed in the image processing apparatus 300 by setting a CD-ROM in which the image processing program is recorded in the CD-ROM device 316.

  In the image processing system according to the present invention, an XYZ color system XYZ image is acquired from the three primary color images captured by the field sequential imaging device 10. Note that the XYZ color system is one of the device-independent color systems defined by the CIE (International Lighting Commission).

  Next, a method of calculating conversion parameters (matrix) for converting the three primary color images captured by the field sequential imaging device 10 into XYZ images will be described with reference to FIG. When calculating the conversion parameter (matrix), first, a scene for which colorimetric color reproduction is to be realized is imaged in a frame sequential manner by the frame sequential imaging device 10. Here, the scene to be imaged is, for example, a person or a person including both a person and a color chart in addition to the color chart 400 in which a rectangular area 401 of 24 colors as shown in FIG. 3 is formed.

  RAW data of the three primary colors obtained by this imaging is recorded on the memory card 154. When the memory card 154 is loaded into the card interface 317 of the image processing apparatus 300, the image processing apparatus 300 reads out the RAW data of the three primary colors as appropriate. As shown in FIG. 2, the frame sequential imaging device 10 may be connected to a communication interface 327 such as IEEE1394 or USB, and RAW data may be read from the frame sequential imaging device 10.

  FIG. 4 is a flowchart illustrating a processing flow in the image processing apparatus 300 when calculating conversion parameters (matrix) for converting the three primary color images captured by the field sequential imaging apparatus 10 into XYZ images. First, RAW data of a scene imaged in the frame sequential order by the frame sequential imaging device 10 is captured (step S10). The RAW data fetched in step S10 is subjected to predetermined processing such as honeycomb interpolation and temporarily stored.

The RAW data is used when a RAW image is displayed on the monitor 320, and color image values (R _n , G _n , B _n ) of each color of the captured scene are calculated (step S12). In this embodiment, as an example, color image values (R _n , G _n , B _n ) are calculated for 24 colors (that is, n = 1,..., 24). Then, the color image values (R _n , G _n , B _n ; n = 1,..., 24) calculated from the RAW data are sent to the image processing apparatus 300, and a color image of the three primary colors is processed by a process described later. A conversion matrix A (3 × 3) for conversion to an XYZ image is calculated.

The color image values (R _n , G _n , B _n ; n = 1,..., 24) calculated from the RAW data calculated in step S12 are acquired and the XYZ values (X _n ) of the captured scene are acquired. , Y _n , Z _n ; n = 1,..., 24) are acquired (step S14). The XYZ values (X _n , Y _n , Z _n ; n = 1,..., 24) of the imaged scene were obtained by calculating from spectral data and color matching functions measured in advance by a spectral luminance meter. It is a colorimetric value.

Next, the color image values (R _n , G _n , B _n ; n = 1,..., 24) acquired in steps S12 and S14, and the XYZ values (X _n , Y _n , Z _n ; n = 1) ,..., 24) are substituted into the following equation (1) to calculate the conversion matrix A (α, β, γ) (step S16).

なお、式（１）の（Ｒ_ｎ´，Ｇ_ｎ´，Ｂ_ｎ´；ｎ＝１，…，２４）は、次に示す式（２）により表されるように、色画像値（Ｒ_ｎ，Ｇ_ｎ，Ｂ_ｎ）からそれぞれのチャンネルにおける未知のフレア量（α，β，γ）が減算されたものである。

It should be noted that (R _n ′, G _n ′, B _n ′; n = 1,..., 24) in Expression (1) is expressed by the color image value (R _n , G _n , B _n ), the unknown flare amount (α, β, γ) in each channel is subtracted.

次に、フレア量（α，β，γ）に所定の値（仮定フレア量）が順次代入されて、次に示す式（３）により、代入されたフレア量（α，β，γ）の値ごとにＸＹＺ値（Ｘ_ｎ´，Ｙ_ｎ´，Ｚ_ｎ´；ｎ＝１，…，２４）が算出される（ステップＳ１８）。ここで、仮定フレア量は、例えば、０≦α，β，γ≦２０の範囲の任意の値である。

Next, a predetermined value (assumed flare amount) is sequentially substituted into the flare amount (α, β, γ), and the value of the assigned flare amount (α, β, γ) according to the following equation (3) XYZ values each _{(X n ', Y n'} , Z n '; n = 1, ..., 24) is calculated (step S18). Here, the assumed flare amount is an arbitrary value in the range of 0 ≦ α, β, γ ≦ 20, for example.

その次に、上記ステップＳ２０において、仮定フレア量の値ごとに算出されたＸＹＺ値（Ｘ_ｎ´，Ｙ_ｎ´，Ｚ_ｎ´；ｎ＝１，…，２４）が、次に示す式（４）によりＬ＊ａ＊ｂ＊表色系（Ｌａｂ表色系）のＬａｂ値（Ｌ_ｎ´，ａ_ｎ´，ｂ_ｎ´；ｎ＝１，…，２４）に変換される。また、上記ステップＳ１４において取得された（Ｘ_ｎ，Ｙ_ｎ，Ｚ_ｎ；ｎ＝１，…，２４）も同様にＬａｂ値（Ｌ_ｎ，ａ_ｎ，ｂ_ｎ；ｎ＝１，…，２４）に変換される。

Next, in step S20, the XYZ values (X _n ′, Y _n ′, Z _n ′; n = 1,..., 24) calculated for each value of the assumed flare amount are expressed by the following equation (4 ) Are converted into Lab values (L _n ′, a _n ′, b _n ′; n = 1,..., 24) in the L * a * b * color system (Lab color system). Further, acquired in step _{S14 (X n, Y n,} Z n; n = 1, ..., 24) likewise Lab value _{(L n, a n, b} n; n = 1, ..., 24) Is converted to

なお、式（４）において、（Ｘ_ｌ，Ｙ_ｌ，Ｚ_ｌ）は光源のＸＹＺ値であり、例えば、撮像されたシーン中の白色のＸＹＺ値から算出される。また、関数ｆ（Ｘ_ｎ´／Ｘ_ｌ）は、次に示す式（５）により表される。また、関数ｆ（Ｙ_ｎ´／Ｙ_ｌ）、ｆ（Ｚ_ｎ´／Ｚ_ｌ）も式（５）と同様に表される。

In Equation (4), (X ₁ , Y ₁ , Z ₁ ) is the XYZ value of the light source, and is calculated from, for example, the white XYZ value in the captured scene. The function f (X _n ′ / X _l ) is expressed by the following equation (5). The functions f (Y _n ′ / Y _l ) and f (Z _n ′ / Z _l ) are also expressed in the same manner as in the equation (5).

そして、代入された仮定フレア量の値ごとに、次に示す式（６）により色差が算出され、この色差の平均値Ｅ（α，β，γ）が算出される（ステップＳ２０）。

Then, for each value of the assumed amount of assumed flare, a color difference is calculated by the following equation (6), and an average value E (α, β, γ) of the color difference is calculated (step S20).

その次に、ステップＳ２０において算出された色差の平均値Ｅ（α，β，γ）が最小となるフレア量（α´，β´，γ´）が取得され（ステップＳ２２）、変換マトリクスＡ（α´，β´，γ´）が取得される（ステップＳ２４）。

Next, the flare amount (α ′, β ′, γ ′) that minimizes the average value E (α, β, γ) of color differences calculated in step S20 is acquired (step S22), and the conversion matrix A ( (α ′, β ′, γ ′) is acquired (step S24).

  The conversion matrix A (α ′, β ′, γ ′) calculated as described above is output to the image processing apparatus 300 as a parameter file. Then, based on the conversion matrix A (α ′, β ′, γ ′) and the color image value calculated from the RAW data of the scene imaged by the frame sequential imaging device 10, the same as in the equation (3). An XYZ value is calculated and a colorimetric color reproduction image (XYZ image) is created.

  In steps S20 to S24, a weighted average value of color differences is calculated by the following equation (7) instead of the above equation (6), and the flare amount (α ′, β ′ at which the weighted average value is minimized). , Γ ′), the conversion matrix A (α ′, β ′, γ ′) may be acquired. In this case, for example, by increasing the weight S (i) applied to the color difference of a specific color, the accuracy of the XYZ value of that color can be selectively increased.

本実施形態の画像処理システムにより、３種類の光源下において変換マトリクスＡ（α´，β´，γ´）から求められたＸＹＺ値と、実測値の精度比較を行った。図５は各光源の波長と強度の関係を示すグラフであり、図６は光源ごとの平均色差を示すテーブルである。図６に示すように、すべての光源１から３のもとにおいて、本実施形態のフレア補正を行った場合の平均色差ΔＥの方がフレア補正を行わなかった場合のΔＥよりも小さい。これにより、本実施形態によれば、高解像度かつ高精度の測色的色再現画像（ＸＹＺ画像）を得ることができることが確認された。本実施形態の画像処理システムにより得られるＸＹＺ画像は、製品の色の評価、印刷などの分野での利用が期待できる。

With the image processing system of this embodiment, the XYZ values obtained from the conversion matrix A (α ′, β ′, γ ′) and the measured values were compared under three types of light sources. FIG. 5 is a graph showing the relationship between the wavelength and intensity of each light source, and FIG. 6 is a table showing the average color difference for each light source. As shown in FIG. 6, for all light sources 1 to 3, the average color difference ΔE when the flare correction of the present embodiment is performed is smaller than ΔE when the flare correction is not performed. Thereby, according to this embodiment, it was confirmed that a high-resolution and highly accurate colorimetric color reproduction image (XYZ image) can be obtained. The XYZ image obtained by the image processing system of the present embodiment can be expected to be used in fields such as product color evaluation and printing.

  In the present embodiment, the case where an XYZ image is obtained from a color image of three primary colors in sequential order has been described. However, the present invention also applies to a case where a colorimetric color reproduction image (for example, a Lab image) other than an XYZ image is obtained. Applicable. In this embodiment, the case where a 3 × 3 matrix is used for conversion into an XYZ image has been described, but the conversion parameter calculation method according to this embodiment is also used when a three-dimensional lookup table (3D-LUT) is used. Applicable. Further, the frame sequential color image may be, for example, a frame sequential RGB image using an RGB color filter or a frame sequential CMY image using a CMY color filter. Furthermore, the present invention can also be applied to a case where a colorimetric color reproduction image is acquired from a frame sequential color image using four or more color filters.

  In this embodiment, an example of converting a color image of the three primary colors captured in the field sequential order into an XYZ image has been described. However, when converting a color image of the three primary colors captured by a digital camera or the like into an XYZ image. Also, the image processing method of this embodiment can be applied.

  In addition, by applying software and firmware including a program for performing the above-described processing to a device having an image playback function, such as a personal computer (PC), a video playback device (video deck, television), or a digital camera, the present invention The image processing method and the image processing system can be realized.

1 is a block diagram showing a field sequential imaging device constituting an image processing system according to an embodiment of the present invention. 1 is a block diagram showing an example of a hardware configuration of an image processing apparatus constituting an image processing system according to the present invention. Plan view schematically showing the color chart The flowchart which shows the flow of a process in the image processing apparatus 300 at the time of calculating the conversion parameter (matrix) for converting the color image of three primary colors imaged with the field sequential imaging device 10 into an XYZ image. Graph showing the relationship between the wavelength and intensity of each light source Table showing the average color difference for each light source

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Frame sequential imaging device, 100 ... Imaging device main body, 112 ... Imaging lens, 114 ... Aperture, 116 ... Monochrome imaging device, 118 ... Analog signal processing part, 120 ... A / D converter, 122 ... Image input controller, 124 DESCRIPTION OF SYMBOLS Digital signal processing part 126 ... Compression / decompression processing part 128 ... Video encoder 130 ... Liquid crystal monitor 132 ... Image sensor control part 134 ... Aperture drive part 136 ... Lens drive part 137 ... Filter drive part 138 ... Operation part 140 ... Central processing unit (CPU) 142 ... AF detection part 144 ... AE detection part 148 ... Memory (SDRAM) 150 ... VRAM 151 ... ROM 152 ... Media controller 154 ... Memory card , 200 ... Rotating color filter device, 202 ... Turret plate, 204 ... Motor, 300 ... Image processing device 310 ... Central processing unit (CPU), 312 ... Main memory, 314 ... Hard disk device, 316 ... CD-ROM device, 317 ... Card interface (card I / F), 318 ... Display memory, 320 ... Monitor device, 322 ... Keyboard, 324 ... mouse, 326 ... mouse controller, 327 ... communication interface (communication I / F), 328 ... bus, 400 ... color chart

Claims (5)

In a conversion parameter calculation method for calculating a conversion parameter for obtaining a colorimetric color reproduction image from at least three primary color images,
(A) obtaining a color image of at least three primary colors obtained by imaging a scene for which colorimetric color reproduction is desired;
(B) Assuming the flare amount generated at the time of acquisition of the color image, the color of the scene based on the assumed flare amount, the color image value of the scene, and the colorimetric value measured for the scene Calculating a conversion parameter for converting an image value into the colorimetric value;
(C) a colorimetric value calculation step of calculating a colorimetric value of the scene based on the color image value of the scene and the calculated conversion parameter;
(D) Based on the colorimetric value measured for the scene and the colorimetric value calculated in the step (c), the weighted average value of the color difference when the weight applied to the color difference of a specific color is increased is calculated. And a process of
(E) A flare amount calculating step for obtaining a flare amount that minimizes the weighted average value of the color differences by repeating the steps (b) to (d) while changing the assumed flare amount;
(F) obtaining a conversion parameter based on a flare amount that minimizes the average value of the color differences;
A conversion parameter calculation method comprising: The colorimetric value of the light source of the scene is calculated from the colorimetric value of white in the captured scene, and the conversion parameter is calculated based on the colorimetric value of the light source . Conversion parameter calculation method.   3. The conversion parameter calculation method according to claim 1, wherein the colorimetric color reproduction image is an XYZ color system XYZ image or a Lab color system Lab image. In a conversion parameter calculation program for calculating a conversion parameter for obtaining a colorimetric color reproduction image from at least three primary color images,
A function for acquiring a color image of at least three primary colors obtained by imaging a scene for which colorimetric color reproduction is desired;
Assuming the amount of flare generated when acquiring the color image, the color image value of the scene is calculated based on the assumed flare amount, the color image value of the scene, and the colorimetric value measured for the scene. A function for calculating a conversion parameter for conversion to the colorimetric value;
A function for calculating a colorimetric value of the scene based on the color image value of the scene and the calculated conversion parameter;
A function of calculating a weighted average value of color differences when a weight applied to a color difference of a specific color is increased based on the colorimetric value measured for the scene and the calculated colorimetric value;
A function of repeatedly calculating the average value of the color differences while changing the assumed flare amount to obtain a flare amount that minimizes the weighted average value of the color differences;
A function of acquiring a conversion parameter by a flare amount that minimizes the average value of the color difference;
A conversion parameter calculation program for causing a computer to realize the above. Image acquisition means for acquiring a color image of at least three primary colors obtained by imaging a scene for which colorimetric color reproduction is desired;
Assuming a plurality of flare amounts generated at the time of obtaining the color image, based on the color image value of the scene and the colorimetric value measured for the scene, the color image value of the scene for each of the assumed flare amounts Conversion parameter calculation means for calculating a conversion parameter for converting the colorimetric value into the colorimetric value;
A colorimetric value calculating means for calculating a colorimetric value for calculating the colorimetric value of the scene based on the color image value of the scene and the calculated conversion parameter;
Color difference average value calculating means for calculating a weighted average value of color differences when the weight applied to the color difference of a specific color is increased based on the colorimetric values measured for the scene and the calculated colorimetric values;
A flare amount calculating means for comparing the average values of the color differences calculated for each of the assumed flare amounts and obtaining a flare amount that minimizes the weighted average value of the color differences;
Conversion parameter acquisition means for acquiring a conversion parameter by a flare amount that minimizes the average value of the color differences;
A calorimetric color reproduction means for obtaining a calorimetric color reproduction image based on the obtained conversion parameter when an image of at least three primary colors is input via the image acquisition means;
An image processing apparatus comprising:

Images