JPH0448890A - Picture correction device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image correction device that corrects the illumination conditions of an input digital color image and outputs the corrected image.

[Prior Art] In conventional digital image processing devices, when a user attempts to obtain a corrected image under a desired illumination condition from an input image under a certain actual illumination condition, the input image is For example, a method of correcting brightness using a lookup table and a method of correcting color using a matrix have been used. However, in these conventional methods, the user must determine the values of the lookup table and matrix by intuition, and therefore, the corrected image obtained using these correction parameters may spoil the image of the input image. Ta.

Furthermore, when obtaining an image from a photograph using conventional technology, an optical filter such as a CC filter (color convensating filter) is used at the time of photography to partially weaken some of the red, green, and blue components of the spectrum. How to change the color balance of images shot on color film by using the LB filter (which is also an optical filter)
A method of changing the color balance of images shot on color film by using a light balancing filter (light balancing filter) to change the color temperature of the light source and making adjustments to strengthen or weaken the red, green, and blue parts of the spectrum as a whole. , and methods using a combination of these optical filters have been used. However, in these conventional methods, experts select the above-mentioned optical filters based on knowledge gained through experience,
It has been nearly impossible to obtain properly corrected images except when shooting in combination.

[Problems to be Solved by the Invention] As described above, in conventional image correction techniques, the user has no choice but to determine the correction parameters for the target illumination condition based on his or her intuition, and as a result, the brightness and color of the obtained corrected image are There was a problem that needed to be solved in that it was not possible to appropriately correct conditions such as the following.

Also, if you try to correct the lighting conditions with an optical filter when taking a photo, it may be difficult to obtain a photographic image under the desired lighting conditions, as optical filters can only make corrections according to their unique characteristics. There was an issue that needed to be solved that could not be done.

An object of the present invention is to solve the above problems and provide an image correction device that can appropriately convert an input image under a certain lighting condition into an image under a target lighting condition and output the image. There is a particular thing.

[Means for Solving the Problem] In order to achieve the above object, the present invention provides an image input means for inputting a digital color image, and a plurality of illumination condition correction parameters for one condition, which are input in advance from actual measurement data. a storage means for storing the digital color image obtained from the image input means, a correction means for converting the digital color image input from the image input means into a corrected image based on the storage means, and outputting the corrected image obtained by the correction means. The invention is characterized by comprising an output means for.

The present invention also provides an image input means for inputting digital color images, data obtained from photographing color charts in a plurality of cloudy-weather dies, and data obtained from photographing the same color chart in a certain appropriate fair-weather die. A plurality of illumination condition correction parameters are obtained and stored in advance by associating them with each other. a storage means, and a correction means for converting a digital color image of illumination conditions under a cloudy sky input from the image input means into a corrected image using illumination condition correction parameters corresponding to the cloudy weather condition stored in advance in the storage means. and an output means for outputting the corrected image obtained by the correction means.

[Function] In the present invention, the illumination data obtained from a plurality of pieces for one condition is stored in the storage means, and the input original image is converted into a corrected image based on the illumination condition correction parameters and then output. .

In addition, the present invention converts an input image under cloudy lighting conditions into a corrected image using lighting condition correction parameters according to the cloudy state, and then outputs the image. A plurality of pieces of data are obtained by associating data obtained from actually photographing a color chart on that cloudy day with data obtained from actually photographing the same color chart on a certain appropriate sunny day, and stored in a storage means. Te(.

In this way, since it is based on actual measurement data, the user can obtain an output image with the illumination conditions of the input image corrected without relying on intuition. Furthermore, it is possible to save the effort of taking photographs again under favorable conditions.

Embodiments] Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a circuit configuration of an image correction device according to an embodiment of the present invention. In this figure, numeral 1 indicates a subject such as a person or scenery to be photographed. Reference numeral 2 denotes an image photographing device for photographing the subject 1, such as a camera. Reference numeral 3 denotes an image input device for inputting images photographed by the image photographing device 2, and a drum scanner is used, for example. 3' is a command input device for giving instructions to each part, and for example, a keyboard is used. 4 is a display device for displaying input commands, illumination condition correction parameters, input images, and images after correction processing; for example, a display using a CRT (cathode ray tube) or liquid crystal is used. .

6 is a file device for storing illumination condition correction parameters; for example, a brightness correction lookup table and a color correction coefficient matrix, which are illumination condition correction parameters from cloudy to sunny conditions, are stored in advance as described below. .

As this file device 6, for example, in addition to a memory such as an IC-RAM, an FD (floppy disk) or a CD (compact disk) can be used. Reference numeral 7 denotes a calculation device that performs calculation processing on the input image based on the illumination condition correction parameters stored in the file device 6 . As the arithmetic unit 7, for example, a microcomputer or an arithmetic circuit can be used.

Reference numeral 8 denotes an output device for obtaining a hard copy, such as a digital film recorder. Reference numeral 5 denotes a control device which displays the above-mentioned input device 39 and display device 4. File device 6. It controls the arithmetic device 7 and the output device 8. As the control device 5, for example, a one-chip microcomputer having a built-in program ROM, RAM, etc. is used.

The operation of the image correction apparatus of this embodiment configured as described above will be explained below according to the flow of data.

In FIG. 1, a photographic signal of a subject (for example, a person) 1 photographed by a photographing device 2 under illumination conditions under a cloudy sky is converted by an image input device 3 (A/DC analog/digital), and then sent to a control device 5. The image is stored in the file device 6 as an original image under the control of.

Next, the control device 5 calls up the original image stored in the file device 6, and performs a brightness correction process using a brightness correction lookup table stored in advance in the file device 6, and a color correction process using a color correction coefficient matrix. A corrected image is obtained by performing the calculation process 7, and this corrected image is stored in the file device 6. Next, the corrected image is output as a hard copy onto a recording medium such as positive film by the output device 8.

In this way, an output image in which the illumination conditions of the original image are corrected can be obtained from the output device 8 according to the illumination condition correction parameters stored in the file device 6.

FIGS. 2 and 3 are graphs showing an example of the data contents of the brightness correction lookup table of the file device 6, in which the horizontal axis shows the input gradation and the vertical axis shows the output gradation. Figure 2 shows the standard state, in which a gradation value of O is output for an input of a gradation value of 0, and a gradation value of 2 is output for an input of a gradation value of 255.
55, indicating a directly proportional correlation, and the contents of the input and output are the same. Furthermore, FIG. 3 shows that there is an inversely proportional correlation in which a gradation value of 255 is output for an input of a gradation value of 0, and a gradation value of O is output for an input of a gradation value of 255. When the lookup table shown in FIG. 3 is used, the relationship between input and output is an image in which the density data is inverted. Here, for convenience, the red that constitutes each pixel of the digital image.

Green and blue data are represented by R, G, and B, respectively. Furthermore, each pixel has an 8-bit configuration for each component, that is, data that can be expressed in 256 gradations, with the highest brightness being 255 and the lowest brightness being O.

The following equation (1) represents the color correction matrix processing executed by the arithmetic unit 7 described above.

The above formula (1) is Ril'l+G, which is the RGB value of the input image.
l. .

Rout+GIlut+B which is the RGB value of the output image using 3×3 coefficient matrix A=(alJ) from Blrl
It shows that OLlt is obtained.

Here, if the matrix in (2) below is used as the coefficient matrix A in equation (1) above, it indicates a standard state, and the input and output contents are the same.

Furthermore, when the matrix in (3) below is used as the relational matrix A in (1) above, Rout is Bln, Gaut is Gin, and Bout is R111.

The flowchart of FIG. 4 shows the operating procedure of the illumination condition correction process (process of obtaining an image of a person under clear sky illumination conditions from an image of a person under cloudy sky illumination conditions) in the embodiment of FIG. 1.

The processing operation of this embodiment will be described in detail below with reference to the flowchart of FIG.

A user places a positive film taken by a camera, which is an image capturing device 2, on a drum (not shown) of a drum scanner, which is an image input device 3, under cloudy lighting conditions. , sends instruction information for starting processing to the control device 5 from the command input device 3'. When the control device 5 receives the instruction information, it sends a command to start scanning (image scanning) to the image input device W3, and as a result, the image input device W3 outputs an image 8.
The RGB data quantized into bits is stored as an original image in the file device 6 for each pixel.

At the end of the process S2, the original image in the file device 6 is displayed on the display device 4 according to a command from the control device 5.

Next, according to the command from the control device 5, the command input device 3'
is in a command input waiting state, and the user manually selects and inputs a brightness correction lookup table and a color correction coefficient matrix according to the cloudy condition of the original image using the keys on the command input device 3'.

Next, in response to a command from the control device 5, the arithmetic device 7 performs brightness correction, which is the first stage of the illumination condition correction process. That is,
The arithmetic device 7 processes the image data stored in the file device 6 (
each pixel R, G of the original image).

The brightness is corrected for each value of B using the brightness correction lookup table described above.

The contents of this lookup table are determined in advance and stored in the file device 6 based on measurement data under each of the cloudy and clear lighting conditions. FIG. 5 shows an example of specific contents of the lookup table used in the embodiment. In this embodiment, the same table is used for each of R, G, and B values. The image data is stored in the file device 6 again after the brightness correction process.

Next, in response to a command from the control device 5, the arithmetic device 7 performs color correction, which is the second stage of the illumination condition correction process. That is, the calculation device 7 performs matrix calculations on the R, G, and B values of each pixel of the image data stored in the file device 6 using the above color correction coefficient matrix. Similarly to the above, the contents of the color correction coefficient matrix are obtained in advance and stored in the file device 6 from measurement data under each of the cloudy and clear lighting conditions. An example of the specific contents of the coefficient matrix used in this example is shown in (4) below. After the image data is subjected to color correction processing, it is stored again in the file device 6.

Next, according to a command from the control device 5, the corrected image in the file device 6 is displayed on the display device 4.

Next, according to the command from the control device 5, the command input device 3'
enters a command input waiting state, and here the user checks the corrected image displayed on the display device 4, and if the user determines that this is acceptable, the process proceeds to step S8; if the user determines that this is not correct, the process proceeds to step S2. Key human power to return to.

According to a command from the control device, the contents of the image data in the file device 6 are outputted onto a positive film by the digital film recorder, which is the output device 8, and the process is completed.

In the above-described embodiment, an image is input from a photographed positive film using a drum scanner, but the same effect can be obtained by inputting from a photographic print or a printed matter. Also,
Although a drum scanner was used as the input device, the same effect can be obtained by directly inputting an image of a three-dimensional object using a TV camera or the like.

Further, in this embodiment, the same lookup table is used for each of R, G, and B, but it is also possible to use separate lookup tables for each of R, G, and B.

[Effects of the Invention] As explained above, according to the present invention, image correction is performed using illumination condition correction parameters obtained based on actual measurement data, so the user does not have to rely on intuition or experience. It is possible to easily obtain an output image in which the illumination conditions of the input image are corrected to the target illumination conditions without relying on it. Furthermore, it is possible to save the effort of taking photographs again under favorable conditions.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the circuit configuration of an image correction device according to an embodiment of the present invention, FIGS. 2 and 3 are graphs each explaining the contents of the lookup table of this embodiment, and FIG. Flowchart showing the processing operation of one embodiment of the invention. FIG. 5 is a graph showing a specific example of the brightness correction lookup table of this embodiment. 1... Subject, 2... Image capturing device, 3... Image input device, 3'... Command input device, 4... Display device, 5... Control device, 6... File Device, 7... Arithmetic device, 8... Output device. Figure 3

Claims (1)

[Scope of Claims] 1) Image input means for inputting a digital color image; Storage means for storing a plurality of illumination condition correction parameters obtained in advance from actual measurement data for one condition; a correction means for converting a digital color image input from an image input means into a corrected image based on the illumination condition correction parameters stored in advance in the storage means; and an output for outputting the corrected image obtained by the correction means. An image correction device characterized by comprising: means. 2) Correlating the image input means for inputting digital color images with data obtained from photographing color charts on a plurality of cloudy days and data obtained from photographing the same color chart on a certain appropriate sunny day. a storage means in which a plurality of illumination condition correction parameters are obtained and stored in advance; and a digital color image of the illumination condition under cloudy weather inputted from the image input means is stored in advance in the storage means under the cloudy sky. An image correction device comprising: a correction means for converting into a corrected image using illumination condition correction parameters according to a state; and an output means for outputting the corrected image obtained by the correction means.