JPH1155520A - Image processing unit and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the image processing unit by which deterioration in image quality of an input image is prevented by correcting the contrast and intensity without making a dynamic range of gradation of image data narrower and to provide its method. SOLUTION: Received image data are given to an image distribution detection circuit 402, where gradation distribution of the image data is taken and a contrast correction circuit 403 sets a correction parameter of contrast. Furthermore, an intensity adjustment offset value setting circuit 404 adds the contrast correction parameter and an intensity adjustment parameter based on the intensity adjustment parameter set by the user to set a level conversion parameter. An image level conversion circuit 406 converts level of the image data according to the level conversion parameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and method, and more particularly, to an image processing apparatus and method for performing contrast and brightness correction on image data.

[0002]

2. Description of the Related Art Advances in digital signal processing technology, recording and reproduction technology, and recording media have made digital video cameras and digital still cameras widely available at low cost. In addition, personal computers and their peripheral devices have been improved in performance and reduced in price, and individuals are ready to easily handle large amounts of images.

When an image photographed by a digital video camera, a digital still camera, or the like is output by an image output device such as a television monitor or a printer, the dynamic range of gradations of the image data is expanded to improve the image quality. For this purpose, contrast correction is performed.

[0004] This contrast correction will be described with reference to FIGS. 1 and 2.

In FIG. 1, an input terminal 10 for image data is provided.
1 is input to the image distribution detection circuit 10
In 2, the gradation frequency distribution of the image data is obtained as shown in FIG. 2 (1) before the contrast correction. “A” and “B” represent the minimum and maximum levels, respectively.

The image distribution detecting circuit 102 obtains a gradation frequency distribution of the image data, and the result is sent to a contrast correction range setting circuit 103, where a contrast correction parameter is set. For example, a position a of α% with respect to the total number of pixels counted from the minimum value A in the figure before contrast correction of FIG. 2A and a position b of β% with respect to the total number of pixels counted from the maximum value B are obtained. The range of (a, b) is set as a range for contrast correction. The ranges a and b are sent to the contrast correction circuit 105 as contrast correction parameters.

[0007] The memory 104 holds the image data input from the input terminal 101 until the range of the contrast correction is determined. The contrast correction circuit 105 reads image data from the memory 104 and performs contrast correction according to the contrast correction parameters a and b sent from the contrast correction range setting circuit 103. Assuming that the image data read from the memory 104 is x, the contrast correction is f (x) = 255 × (x−a) / (b
-A). The gradation frequency distribution of the image data is shown in FIG.
This is a diagram after the contrast correction of (1). The contrast correction circuit 105 performs the above-described correction on the image data, and outputs the result to the output terminal 106. The user views the contrast-corrected image on an image output device such as a television monitor. At this time, the user may want to adjust the brightness of the corrected image. in this case,
According to the user's operation, the image data subjected to the contrast correction is further corrected.

The operation of adjusting the lightness and darkness of the contrast-corrected image data will be described with reference to FIG. The corrected image data is input from the input terminal 301. The light-dark shift amount setting circuit 304 sets a shift amount (shq) based on user input information from the input terminal 305 and sends the shift amount (shq) to the level shift circuit 302. The level shift circuit 302 shifts the level of the input corrected image data according to the shift amount (shq) sent from the light-dark shift amount setting circuit 304. Assuming that the corrected image data is x, the level shift of the image data is represented by f (x) = x + shq. Thereafter, the corrected image data is output to the output terminal 303, and the user views the image whose brightness has been corrected on an image output device such as a television monitor. The gradation frequency distribution of the pixels of the shifted image data is as shown in FIG. 2B after the brightness correction. Here, what is actually output to an image output device such as a television monitor is in the range of (shq, 255), and image data corresponding to the hatched portion is missing.

[0009]

However, the above technique has the following problems. After performing the contrast correction on the image data to expand the dynamic range, the brightness of the image data after the contrast correction is adjusted by the user's operation. Therefore, the dynamic range is reduced by shifting the gradation frequency distribution of the image data. , 0 to 255, the image corresponding to the image data outside the level range is lost, and the image quality is significantly deteriorated.
Further, there is a problem that the image is easily whitened (the image becomes whitish) and the black is lost (the image becomes dark) due to the light / dark adjustment, and the light / dark adjustment cannot be performed sufficiently satisfactorily.

An object of the present invention is to solve the above-mentioned problem, and to perform contrast and light / dark correction without reducing the dynamic range of the gradation of image data, and to prevent image quality deterioration of an input image. It is an object to provide a processing device and a method thereof.

[0011]

The present invention has the following configuration as one means for achieving the above object.

An image processing apparatus according to the present invention comprises: first input means for inputting image data; setting means for setting a contrast correction parameter based on a level distribution of the input image data; and a brightness adjustment parameter set by a user. A second input unit for inputting, and a correction unit for correcting the input image data based on the contrast correction parameter and the lightness / darkness adjustment parameter.

According to the image processing method of the present invention, image data is input, a contrast correction parameter is set from a level distribution of the input image data, a brightness adjustment parameter set by a user is input, and the contrast correction parameter and Based on the brightness adjustment parameters,
The input image data is corrected.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image processing apparatus and an image processing method according to an embodiment of the present invention will be described in detail with reference to the drawings.

[Basic Configuration] FIG. 4 is a block diagram showing a configuration example of an image processing apparatus according to an embodiment of the present invention.

Image data from a digital video camera or the like is input from an input terminal 401 to a memory 405 and an image distribution detection circuit 402. 5 in the image distribution detection circuit 402.
The contrast and the gradation frequency distribution of the image data as shown in the figure before the brightness correction are obtained, and the result is sent to the contrast correction circuit 403.

The gradation frequency distribution of the image data input to the image distribution detecting circuit 402 is sent to a contrast correction range setting circuit 403, where a contrast correction parameter is set. For example, a position a of α% with respect to the total number of pixels counted from the minimum value A in the figure before the contrast and contrast correction of FIG. The range of a, b) is set as a range for contrast correction. Data a and b indicating the range are sent to the contrast adjustment offset value setting circuit 404 as contrast correction parameters.

The light / dark adjustment offset value setting circuit 404
Contrast correction parameters a and b and light / dark adjustment parameters (offset) set by user operation
And are added. Data (a + offset) and (b + off) indicating the range are provided to the image level conversion circuit 406.
set) as a level conversion parameter.

The image level conversion circuit 406 has the level conversion parameters (a + offset) and (b + offset) set by the light / dark adjustment offset value setting circuit 404.
According to t), the image data is read from the memory 405 and the level of the image data is converted. Assuming that the image data read from the memory 405 is x, the level conversion is f (x)
= 255 x (x- (a + offset)) / (ba)
It is represented by The level-converted image data as shown in the figure after the contrast and brightness correction in FIG. 5 is output from the image level conversion circuit 406 to the output terminal 407.

When image data is first input,
The light-dark adjustment parameter (offset) of the light-dark adjustment offset value setting circuit 404 is offset = 0. Therefore, the image data is level-converted based on the contrast correction parameters a and b and output from the output terminal 407. The user adjusts the brightness of the image based on the result. The light-dark adjustment offset value setting circuit 404 sets a light-dark adjustment parameter (offset) based on light-dark adjustment input information from the input terminal 408.

FIG. 6 is a block diagram showing an example of the configuration of an image processing apparatus when the image processing described with reference to FIG. 4 is realized by software.

The computer bus 604 interfaces a main memory (RAM) 601, a CPU 602, a ROM 603, an input interface unit 605, and a video interface unit 606.

Image data output from a device 607 such as a video camera is input from an input interface unit 605. This input interface unit 604 is connected to the IE
EE1394, SCSI, GPIB, RS232C, R
A general-purpose interface such as S422 can be used.

The ROM 603 stores program steps corresponding to the flowchart shown in FIG.
The CPU 602 reads the main memory (RA
M) A program step is loaded into 601 and the program step is executed on image data input from the input interface unit 605. The result is output to an image output device such as a monitor 608 through the video interface unit 606.

The flow of the above processing will be described in detail with reference to the flowchart of FIG.

In step S1, image data is input from the input terminal 401 of FIG. A step S2 calculates a gradation frequency distribution of the image data input in the step S1. In step S3, contrast correction parameters a and b are obtained based on the gradation frequency distribution of the image data obtained in step S2. A step S4 sets an initial value offset = 0 for the brightness adjustment parameter. Step S
5 adds the contrast correction parameters a and b obtained in step S3 and the initial value offset = 0 of the light-dark adjustment parameter set in step S4, and sets the level conversion parameters (a + offset, b + offset). In step S6, the level conversion parameters (a + offset, b + off) set in step S5
Set), level conversion of image data is performed. A step S7 outputs the image whose level has been converted in the step S6. Step S8 is performed when it is necessary to further adjust the brightness of the image output in step S7.
Proceed to.

In step S9, if the image output in step S7 is to be brightened, a negative light / dark adjustment parameter (o
ffset), and if darkening is desired, a positive light / dark adjustment parameter (offset) is input. Thereafter, the process returns to step S5, and the level conversion parameters (a + offset) and (b + offset) according to the brightness adjustment parameter (offset) input in step S9.
To reset. In step S6, the reset level conversion parameters (a + offset) and (b + off)
Set), level conversion of image data is performed. A step S7 outputs the image whose level has been converted in the step S6. Step S8 is performed when it is necessary to further adjust the brightness of the image output in step S7.
The process proceeds to steps S5, S6, S7, and S8, and if not, the flow ends.

In the embodiment described above, the contrast and light / dark correction are performed without narrowing the dynamic range of the gradation of the image data by adding the contrast correction parameter of the image data and the light / dark adjustment parameter. Can be prevented.

It should be noted that the present invention is not limited to the above-described embodiment, but can be applied to, for example, an image processing apparatus such as a laser beam printer. Further, the present invention is not limited to the above-described circuit configuration, and can be applied to an apparatus having a configuration using the above-described means.

[0030]

[Other Embodiments] Even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus (for example, a copying machine) Machine, facsimile machine, etc.).

Another object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or apparatus, and to provide a computer (or CPU) of the system or apparatus.
And MPU) read and execute the program code stored in the storage medium. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk,
D-ROM, CD-R, CD-R / W, DVD-RO
M, DVD-RAM, magnetic tape, non-volatile memory card, ROM, and the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also an OS (Operating System) running on the computer based on the instruction of the program code. ) May perform some or all of the actual processing, and the processing may realize the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written in a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the program code is read based on the instructions of the program code. It goes without saying that a CPU or the like provided in the function expansion card or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0034]

The present invention provides an image processing apparatus and method capable of performing contrast and light / dark correction without reducing the dynamic range of the gradation of image data and preventing deterioration of the image quality of an input image. be able to.

[0035]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a general contrast correction circuit.

FIG. 2 is a diagram for explaining general contrast correction and light / dark adjustment;

FIG. 3 is a block diagram showing a configuration example of a general light-dark adjustment circuit;

FIG. 4 is a block diagram showing a configuration example of an image processing apparatus according to an embodiment of the present invention;

FIG. 5 is a view for explaining contrast correction and light / dark adjustment according to the present invention;

FIG. 6 is a block diagram illustrating a configuration example of an image processing apparatus when image processing according to an embodiment of the present invention is implemented by software;

FIG. 7 is a flowchart illustrating an image processing method according to an embodiment of the present invention.

Claims (13)

[Claims] A first input unit for inputting image data; a setting unit for setting a contrast correction parameter based on a level distribution of the input image data; and a second input for inputting a brightness adjustment parameter set by a user. Means for correcting the input image data based on the contrast correction parameter and the lightness / darkness adjustment parameter. 2. The image processing apparatus according to claim 1, wherein the correction unit corrects the input image data with a level conversion parameter obtained by adding the contrast correction parameter and the lightness / darkness adjustment parameter. 3. The image processing apparatus according to claim 2, wherein the correction unit extends a dynamic range of gradation of the input image data based on the level conversion parameter. 4. The image processing apparatus according to claim 2, wherein the correction unit performs a contrast correction process and a light / dark adjustment process based on the level conversion parameter. 5. The image processing apparatus according to claim 1, wherein the contrast correction parameter represents a predetermined range of the level distribution. 6. The image processing apparatus according to claim 1, wherein the brightness adjustment parameter is set by a user according to brightness of an image represented by the input image data. Image processing device. 7. The level conversion parameter according to claim 2, wherein the contrast correction parameter is a and b, and the brightness adjustment parameter is c, and the level conversion parameter is represented by a + c and b + c. The image processing apparatus according to any one of the above. 8. The correction by the correction means is as follows: when the image data is x, f (x) = 255 × (x− (a +
8. The image processing apparatus according to claim 7, wherein c)) / (ba). 9. The apparatus according to claim 1, wherein the first input unit includes an interface for inputting image data output from a digital camera or the like. Image processing device. 10. The image processing apparatus according to claim 1, wherein the second input unit includes an interface for allowing a user to perform light / dark adjustment. 11. The image processing apparatus according to claim 1, wherein the correction unit includes an interface for outputting the processed image data to an image output device. apparatus. 12. Inputting image data, setting a contrast correction parameter from a level distribution of the input image data, inputting a light / dark adjustment parameter set by a user, based on the contrast correction parameter and the light / dark adjustment parameter, An image processing method, wherein the input image data is corrected. 13. A recording medium on which a program code for image processing is recorded, wherein a program code for setting a contrast correction parameter from a level distribution of the input image data; and the contrast correction parameter and the brightness adjustment parameter. A program code for correcting the input image data based on the program code.