JP2006109313A - Image processing apparatus and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology of providing a properly modulated image preferable for a certificate photo wherein details of a face of a person are properly suppressed. <P>SOLUTION: An image processing apparatus 1 applies contrast characteristic conversion processing to image data obtained by photographing to convert the image data so that a change amount of a lightness L* in the output is a multiple of 0.9 to 2.5 with respect to a change amount in the lightness L* in the input in a medium and low lightness region of the image (35≤L*≤50), and a change amount of a lightness L* in the output is a multiple of 0.2 to 0.9 with respect to a change amount in the lightness L* in the input in a medium and high lightness region of the image (65≤L*≤80). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus and an image processing method for performing image processing on an input image and outputting the processed image.

2. Description of the Related Art Conventionally, an apparatus and a system that perform various kinds of image processing on digital image data captured by an image input device such as a digital camera or an image reading device and output the data from a monitor or a printer are known (for example, see Patent Document 1).
JP-A-9-130609

  By the way, it is assumed that the ID photo is used for public purposes, and color reproduction is performed faithfully to the color of the subject, but the ID photo image in the ID photo box is a general snapshot photo, etc. Unlike an image taken in front of a fixed background by a camera with optimized settings under conditions in which subject distance, light distribution, light intensity, illuminance, etc. are properly managed, a fixed color Color conversion image processing faithful to the subject can be performed using the conversion table.

  However, if the subject is reproduced too faithfully, the details may be too clear and there will be too much visual information on the image, which may be inappropriate as an ID photo. Also, if the dynamic range is widened to faithfully reproduce the gradation information of the subject, the contrast may be insufficient depending on the density range, resulting in a sleepy image or a sharp image. On the other hand, if the contrast is increased in order to add sharpness, the effect of using a strobe as illumination may cause the color to fly or collapse in a high lightness region.

  In the above-mentioned Patent Document 1, the dynamic range compression ratio is changed based on the maximum luminance and the minimum luminance of the image signal so that the portion that is too bright and the portion that is too dark can be printed without being crushed. It does not process the face image properly.

  An object of the present invention is to provide a preferable image as an ID photograph with moderate sharpness, in which details of a person's face are moderately suppressed.

In order to solve the above-mentioned problem, the invention described in claim 1
In an image processing apparatus provided with a contrast characteristic converting means for converting and outputting a contrast characteristic of an input image,
In the L * a * b * color system and the lightness range of the input image where the lightness range of the input image is 35 ≦ L * ≦ 50, the contrast characteristic converting means is a lightness L in the output with respect to the amount of change in the lightness L * at the input. In the output range with respect to the change amount of the lightness L * at the input, in the middle / high lightness region where the lightness range of the input image is 65 ≦ L * ≦ 80 so that the change amount of * is 0.9 to 2.5 times. The contrast characteristic is converted so that the amount of change in the lightness L * is 0.2 to 0.9 times.

The invention according to claim 2 is the invention according to claim 1,
In the contrast characteristic conversion means, the change amount of the lightness L * in the output with respect to the change amount of the lightness L * in the input is 1.2 to 2 in the middle and low lightness region where the lightness range of the input image is 35 ≦ L * ≦ 50. In the middle and high brightness regions where the brightness range is 65 ≦ L * ≦ 80, the amount of change in lightness L * in the output with respect to the amount of change in lightness L * in the input is 0.3 to 0. It is characterized in that the contrast characteristic is converted so as to be 8 times.

The invention according to claim 3 is the invention according to claim 1 or 2,
The contrast characteristic conversion means converts the input image so that the output L * value is greater than the input L * value in a medium to high brightness region where the brightness range of the input image is 65 ≦ L * ≦ 80.

The invention according to claim 4 is the invention according to any one of claims 1 to 3,
The contrast characteristic converting means performs the contrast characteristic conversion on a skin color gamut of an input image.

The invention described in claim 5
In an image processing method for converting and outputting the contrast characteristics of an input image,
In the low-lightness region where the lightness range of the input image is 35 ≦ L * ≦ 50 in the L * a * b * color system, the amount of change in lightness L * in the output relative to the amount of lightness L * in the input is 0. In a medium-high brightness region where the brightness range of the input image is 65 ≦ L * ≦ 80 so that the brightness range of the input image is 9 to 2.5 times, the change amount of the brightness L * in the output with respect to the change amount of the brightness L * in the input is It is characterized in that the contrast characteristic is converted so as to be 0.2 to 0.9 times.

The invention according to claim 6 is the invention according to claim 5,
In the middle and low lightness region where the lightness range of the input image is 35 ≦ L * ≦ 50, the change amount of the lightness L * in the output with respect to the change amount of the lightness L * in the input is 1.2 to 2.1 times. In the middle and high brightness region where the brightness range is 65 ≦ L * ≦ 80, the change amount of the lightness L * at the output with respect to the change amount of the lightness L * at the input is 0.3 to 0.8 times. It is characterized by converting contrast characteristics.

The invention according to claim 7 is the invention according to claim 5 or 6,
In the middle and high brightness regions where the brightness range of the input image is 65 ≦ L * ≦ 80, the conversion is performed so that the output L * value is greater than the input L * value.

The invention according to claim 8 is the invention according to any one of claims 5 to 7,
The contrast characteristic conversion is performed on the skin color gamut of the input image.

  According to the first and fifth aspects of the present invention, the change in the lightness L * at the input in the low and medium lightness region where the lightness range of the input image is 35 ≦ L * ≦ 50 in the L * a * b * color system. The lightness L * at the input is such that the amount of change in the lightness L * in the output with respect to the amount is 0.9 to 2.5 times, and the lightness range of the input image is in the middle / high lightness region of 65 ≦ L * ≦ 80. The contrast characteristic is converted so that the amount of change in the lightness L * in the output with respect to the amount of change in is 0.2 to 0.9 times. Therefore, by applying it to ID photos, it is possible to prevent the image from being reproduced too faithfully in the low and medium brightness areas, resulting in too much detail, and the detail being moderately suppressed and properly sharpened. It is possible to provide a preferable image in which the light portion is not skipped and the color is not crushed.

  According to the second and sixth aspects of the present invention, the amount of change in the lightness L * in the output with respect to the amount of change in the lightness L * in the input in the middle and low lightness region where the lightness range of the input image is 35 ≦ L * ≦ 50. Is 1.2 to 2.1 times, and the amount of change in the lightness L * in the output with respect to the amount of change in the lightness L * in the input in the lightness range of 65 ≦ L * ≦ 80. The contrast characteristics are converted so that becomes 0.3 to 0.8 times. Therefore, by applying the method to the ID photo, it is possible to provide a preferable image having a more appropriate sharpness and without losing the highlight portion.

  According to the third and seventh aspects of the invention, since the lightness range of the input image is converted so that the output L * value> the input L * value in the medium / high lightness region where 65 ≦ L * ≦ 80, It is possible to increase the contrast in the low lightness region to give a sharpness and to secure a sufficient dynamic range.

  According to the fourth and eighth aspects of the present invention, there is no possibility that the image is faithfully reproduced in the medium to low lightness region and the detail is not too clear with respect to the flesh color gamut of the input image, and the detail is moderate. Therefore, it is possible to provide a preferable face image with no sharpness and skipping of highlight portions and color collapse.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the present embodiment, a case where the image processing apparatus according to the present invention is applied to an ID photo box will be described as an example. However, the scope of the invention is not limited to the illustrated examples.

First, the configuration will be described.
FIG. 1 shows an external view of an image processing apparatus 1 according to the present embodiment.
As shown in FIG. 1, the image processing apparatus 1 is formed in a box shape, and an outlet 17a for taking a photographed ID photo is installed on the outer wall thereof. A chair C for the subject M is installed in the box (hereinafter referred to as a photographing room) so that the subject M can be moved up and down. An input device 14 for inputting instructions, a detection sensor 13 for detecting that the subject M has entered the shooting room, and a cashier 23 for adjusting the shooting fee are installed. In addition, lighting strobes 24a to 24f are installed on the inner wall of the photographing room above, on the front, on the back, and below the subject M, respectively.

FIG. 2 shows an internal configuration example of the image processing apparatus 1.
As shown in FIG. 2, the image processing apparatus 1 includes a control unit 11, a camera 12, a detection sensor 13, an input device 14, a display device 15, a storage unit 16, a printer 17, an I / O (Input / Output) unit 21, A speaker 22, a cashier 23, and a strobe unit 24 are provided.

Hereinafter, each part of the image processing apparatus 1 will be described.
The control unit 11 includes a CPU (Central Processing Unit) and a RAM (Random Access Memory), and includes various programs such as a system program stored in the storage unit 16, a face image photographing processing program, and an image processing program according to the present invention. Are expanded in the RAM, and the operation of each unit is centrally controlled according to the program.

The camera 12 includes an optical lens, an optical sensor such as a CCD (Charge Coupled Device), A /
It is composed of a D (Analog / Digital) conversion unit and the like, and at the time of photographing, a subject image input via an optical lens is photoelectrically converted by an optical sensor to generate an image signal (analog). Then, digital image data is obtained from the analog image signal by the A / D conversion unit, and the digital image data is output to the control unit 11.

  The detection sensor 13 is an optical sensor or the like that detects that a user has entered the photographing room of the image processing apparatus 1, and outputs a detection signal to the control unit 11.

  The input device 14 includes a touch panel integrated with the display device 15, a photo type selection switch (hereinafter referred to as SW: Switch) for selecting a photo type, a shooting SW for instructing start of shooting, and a shot image. Various function keys such as a print SW for instructing print output are provided, and an operation signal corresponding to the operated key is output to the control unit 11.

  The display device 15 is configured to include an LCD (Liquid Crystal Display) or the like, and according to a control signal from the control unit 11, various operation screens such as a guide screen for explaining a photographing procedure, a selection screen for selecting a photo type, and the like. The face image of the subject M photographed by the camera 12 is displayed.

  In addition to the system program, the storage unit 16 stores various processing programs such as a face image photographing processing program and an image processing program, data processed by each program, and the like.

  In the present embodiment, the storage unit 16 stores a three-dimensional lookup table (3D-LUT) 161 (details will be described later).

  The printer 17 performs print output based on the image data input from the control unit 11. As a printing method of the printer 17, a sublimation transfer method in which an image is formed by sublimating and transferring a color material will be described. However, by applying heat by superimposing a recording medium and an image receiving material. A melt transfer recording method in which an image is formed by transferring a recording layer of a recording medium to an image receiving layer of an image receiving material may be applied, or an electrophotographic method, an inkjet method, or other printing methods may be used. Moreover, a silver salt photographic image may be formed.

  The I / O unit 21 is an interface that mediates exchange of information between the control unit 11, the speaker 22, the cashier 23, and the strobes 24 a to 24 f, and sends control signals from the control unit 11 to the speaker 22, cashier 23, While transmitting to strobe 24a-24f, the status signal from the speaker 22, cashier 23, strobe 24a-24f, etc. are output to the control part 11. FIG.

  The speaker 22 outputs an audio signal for the guide announcement input from the control unit 11 via the I / O unit 21.

  The cashier 23 is a cash registering machine provided with a coin and banknote deposit port, a change refund port, and the like. The cashier 23 detects the amount deposited from the deposit port, calculates the amount of change, discharges coins or banknotes for the calculated change amount to the refund port, and performs fee settlement.

  The strobe unit 24 includes strobes 24a to 24f, and emits light at a light emission timing and a light emission amount instructed from the control unit 11. As shown in FIG. 1, the strobe 24a is on the ceiling of the photographing room, the strobe 24b is in front of the subject M, the strobe 24c is in front of the subject M (front upper side), the strobe 24d is in the back of the subject M, and the strobe 24e is in front. The strobe 24 f is installed on the lower right side of the subject M and on the lower left side of the subject M.

Next, the operation of the image processing apparatus 1 in the present embodiment will be described.
FIG. 3 is a flowchart for explaining the face image photographing process executed by the control unit 11. This process is a process realized by software processing in cooperation with the CPU of the control unit 11 and the face image photographing processing program stored in the storage unit 16.

  When detection of the user by the detection sensor 13 is awaited and the user is detected by the detection sensor 13 (step S1; YES), a guide screen is displayed on the display device 15 (step S2). At the same time, the announcement sound relating to the photographing guide is output from the speaker 22.

  Next, the charging of the cashier 23 is awaited. When the fee is charged (step S3; YES), the amount of money deposited in the cashier 23 is checked (step S4), and the photo type is displayed on the display device 15. A selection screen for selecting is displayed. When the photo type selection SW corresponding to the desired photo type (for passport, resume, etc.) is pressed on this selection screen (step S5; YES), the charge corresponding to the photo type selected by the cashier 23 Is settled and the change is discharged to the refund slot (step S6).

  When the fee is settled, a shooting guide screen is displayed on the display device 15, and guidance is given to press the shooting SW at a desired timing. When the photographing SW is pressed (step S7; YES), the camera 12 and the strobe unit 24 are controlled, and a face image of the subject M is photographed (step S8).

  After shooting, the image processing program stored in the storage unit 16 is read, and image processing is performed on the image data input from the camera 12 by shooting (step S9).

  When the image processing is completed, the image processed image data is output to the printer 17, and the ID photo is printed out by the printer 17 (step S10). When the ID photo print is discharged to the take-out port 17a (step S11), this process ends.

Next, the image processing performed in step S9 of FIG. 3 will be described.
In step S9, R, G, and B image data input from the camera 12 are subjected to gray balance adjustment processing, spatial filter processing, enlargement / reduction processing, and 3D-LUT 161 contrast characteristic conversion processing.

  The 3D-LUT 161 is a color conversion lookup table that stores a combination of R, G, and B values after conversion corresponding to a combination of R, G, and B values before conversion, and the control unit 11 performs a contrast characteristic conversion process. In this case, a combination of R, G, and B values after conversion corresponding to the R, G, and B values of the image data before conversion is read from the 3D-LUT 161, and the image data input from the camera 12 is converted to capture the image. Thus, the contrast characteristic of the image data input from the camera 12 is converted into a preferable contrast characteristic.

  L1 in FIG. 4 is the brightness before conversion (input) by the 3D-LUT 161 (L * value in the L * a * b * color system defined by the CIE (International Lighting Commission)) and after conversion (output). L0 indicates the relationship with lightness, and L0 indicates the relationship between input and output when lightness is faithfully reproduced in the input image. As shown in FIG. 4, the contrast of the medium / low brightness area (35 ≦ L * ≦ 50 is defined as the medium / low brightness area) compared with the case where the input image is faithfully reproduced by performing conversion using the 3D-LUT 161. Is increased (standing), and the contrast characteristics are converted so that the contrast gradient in the medium / high brightness area (65 ≦ L * ≦ 80 is defined as the medium / high brightness area) is reduced (lays down).

Specifically, by contrast characteristic conversion processing,
In the middle and low lightness region (35 ≦ L * ≦ 50) of the input image, the amount of change in lightness L * in the output (defined as ΔL *) is 0.9 to 2.5 times the amount of lightness L * in input. ,And,
In the middle and high brightness region (65 ≦ L * ≦ 80) of the input image, conversion is performed so that ΔL * is 0.2 to 0.9 times.
More preferably,
ΔL * is 1.2 to 2.1 times in the middle and low brightness region (35 ≦ L * ≦ 50) of the input image, and
In the middle and high brightness region (65 ≦ L * ≦ 80) of the input image, conversion is performed so that ΔL * is 0.3 to 0.8 times.
Also, conversion is performed so that the output L * value> the input L * value in the middle and high brightness region (65 ≦ L * ≦ 80) of the input image.

By the above contrast characteristic conversion process, the face image (skin color area) of the ID photo is not reproduced with too much detail due to the faithful reproduction of the image, and the detail is moderately suppressed and appropriate. It is possible to obtain a preferable image as an ID photo with sharpness. In addition, it is possible to provide an image in which the highlight portion of the face image has no color skip or color collapse.
In addition, by setting the output L * value> the input L * value in the medium / high brightness area, it is possible to increase the contrast in the medium / low brightness area to provide a sharpness and ensure a sufficient dynamic range in the output image. . Furthermore, the medium and high brightness portions can be brightly expressed, and a facial image having a good impression can be obtained.

FIG. 5 shows the results of visual evaluation of real images of ID photos of five researchers (evaluators A to E) engaged in image processing development. Evaluation was carried out by a three-level evaluation, where ◯: very good, Δ: normal, so-so, x: bad.
The ID photo to be evaluated is obtained by taking a person's face image in the ID photo box, converting the obtained image data to contrast characteristics 1 to 5 in FIG. The image was output by a sublimation transfer printer that sublimated and transferred the material to form an image.

As shown in FIG.
(1) When ΔL * is 1.2 to 2.1 times at 35 ≦ L * ≦ 50, and ΔL * is 0.3 to 0.8 times at 65 ≦ L * ≦ 80 (4 in FIG. 5). 4), four evaluators evaluated “◯” and one evaluated “Δ”, and it was verified that a preferable photograph was obtained.
(2) When ΔL * is 0.9 to 2.5 times at 35 ≦ L * ≦ 50, and ΔL * is 0.2 to 0.9 times at 65 ≦ L * ≦ 80 (3 in FIG. 5). 5), one person gave a result of “×”, but there were a plurality of evaluators who gave “◯”, and it was verified that a nearly preferable photograph was obtained.
(3) At least one of ΔL * outside the range of 0.9 to 2.5 times at 35 ≦ L * ≦ 50 or outside the range of ΔL * from 0.2 to 0.9 times at 65 ≦ L * ≦ 80 As for images corresponding to (No. 1, 2, 6, 7 in FIG. 5), it was verified that there were many people who evaluated “x”, and preferable photographs could not be obtained.

  As described above, according to the image processing apparatus 1 of the present invention, the contrast data conversion process is performed on the image data obtained by shooting, and the image data is input in the middle / low brightness region (35 ≦ L * ≦ 50) of the image. Change in lightness L * in the output with respect to the change in lightness L * in the image is 0.9 to 2.5 times, and the change in the lightness L * in the input in the medium to high lightness region (65 ≦ L * ≦ 80) of the image Conversion is performed so that the amount of change in lightness L * in the output with respect to the amount becomes 0.2 to 0.9 times.

  Therefore, in the middle and low brightness areas of the face image of the ID photo, the image is not reproduced too much and the details are not too clear, the details are moderately suppressed, and it is preferable as an ID photo with appropriate sharpness. It can be an image. In addition, it is possible to provide an image in which the highlight portion of the face image has no color skip or color collapse.

In addition, the description content in the said embodiment is a suitable example of the image processing apparatus 1 which concerns on this invention, and is not limited to this.
For example, in the above-described embodiment, the conversion is performed so that all the color gamuts of the input image data have the same contrast characteristic. However, the above-described contrast characteristic is particularly suitable for a face image. Since it is converted into contrast, color reproduction faithfully reproduces the contrast of the original image in the area other than the face area, that is, in the background area other than the combination of the R, G, and B values representing the skin color gamut. Alternatively, the conversion may be performed so that the background region has a preferable contrast.

  In addition, the detailed configuration and detailed operation of the image processing apparatus 1 according to the present embodiment can be changed as appropriate without departing from the spirit of the present invention.

1 is an external view of an image processing apparatus 1 according to the present invention. It is a block diagram which shows the functional structure of the image processing apparatus 1 of FIG. It is a flowchart which shows the face image imaging process performed by the control part 11 of FIG. L1 is a diagram showing the relationship between the lightness L * value before (input) and the lightness L * value after conversion (output) by the 3D-LUT 161, and L0 represents the lightness faithfully reproduced in the input image It is a figure which shows the relationship between input and output. It is a figure which shows the visual evaluation result of an identification photograph.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image processing apparatus 11 Control part 12 Camera 13 Detection sensor 14 Input device 15 Display apparatus 16 Memory | storage part 161 3D-LUT
17 Printer 21 I / O Unit 22 Speaker 23 Cashier 24 Strobe Units 24a-24f Strobe

Claims (8)

In an image processing apparatus provided with a contrast characteristic converting means for converting and outputting a contrast characteristic of an input image,
In the L * a * b * color system and the lightness range of the input image where the lightness range of the input image is 35 ≦ L * ≦ 50, the contrast characteristic converting means is a lightness L in the output with respect to the amount of change in the lightness L * at the input. In the output range with respect to the change amount of the lightness L * at the input, in the middle / high lightness region where the lightness range of the input image is 65 ≦ L * ≦ 80 so that the change amount of * is 0.9 to 2.5 times. An image processing apparatus that converts a contrast characteristic so that a change amount of lightness L * is 0.2 to 0.9 times.   In the contrast characteristic conversion means, the change amount of the lightness L * in the output with respect to the change amount of the lightness L * in the input is 1.2 to 2 in the middle and low lightness region where the lightness range of the input image is 35 ≦ L * ≦ 50. In the middle and high brightness regions where the brightness range is 65 ≦ L * ≦ 80, the amount of change in lightness L * in the output with respect to the amount of change in lightness L * in the input is 0.3 to 0. The image processing apparatus according to claim 1, wherein the contrast characteristic is converted so as to be 8 times.   The contrast characteristic converting means performs conversion so that the output L * value is greater than the input L * value in a medium-high brightness region where the brightness range of the input image is 65 ≦ L * ≦ 80. 2. The image processing apparatus according to 2.   The image processing apparatus according to claim 1, wherein the contrast characteristic conversion unit performs the contrast characteristic conversion on a skin color gamut of an input image. In an image processing method for converting and outputting the contrast characteristics of an input image,
In the low-lightness region where the lightness range of the input image is 35 ≦ L * ≦ 50 in the L * a * b * color system, the amount of change in lightness L * in the output relative to the amount of lightness L * in the input is 0. In a medium-high brightness region where the brightness range of the input image is 65 ≦ L * ≦ 80 so that the brightness range of the input image is 9 to 2.5 times, the change amount of the brightness L * in the output with respect to the change amount of the brightness L * in the input is An image processing method, wherein the contrast characteristic is converted so as to be 0.2 to 0.9 times.   In the middle and low lightness region where the lightness range of the input image is 35 ≦ L * ≦ 50, the change amount of the lightness L * in the output with respect to the change amount of the lightness L * in the input is 1.2 to 2.1 times. In the middle and high brightness region where the brightness range is 65 ≦ L * ≦ 80, the change amount of the lightness L * at the output with respect to the change amount of the lightness L * at the input is 0.3 to 0.8 times. The image processing method according to claim 5, wherein the contrast characteristic is converted.   7. The image processing method according to claim 5, wherein conversion is performed such that the output L * value> the input L * value in a medium-high brightness region where the brightness range of the input image is 65 ≦ L * ≦ 80. .   The image processing method according to claim 5, wherein the contrast characteristic conversion is performed on a skin color gamut of an input image.

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