JP2000270222A - Image processor, image processing method and photographing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology by which gradation of a specific area in an image such as a major object is made proper while utilizing an advantage of density histogram smoothing. SOLUTION: This image processor is provided with an area sensor 6 that reads image information from a negative film, an area extract section 23 that extracts the face of a human body as a specific area from the image information, a histogram generating section 24 that obtains a density histogram from the image information, a lookup tale generating section 26 that generates a smoothing lookup table for smoothing the density histogram, and an image conversion processing section 28 that uses the smoothing lookup table to convert the read image information. Then the image conversion processing is conducted by utilizing advantages of smoothing while keeping the gradation of the face so that a conversion coefficient of the specific area is 1 to 1 in the case of generating the lookup table.

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, an image processing method, and a photographic processing apparatus for smoothing a density histogram obtained from image information.

[0002]

2. Description of the Related Art In the prior art, for example, a method is known in which image information is read from an image frame of a negative film and converted into digital data, and a photograph is formed by exposure in a printing unit using the digital data. In this case, instead of exposing and forming a photograph without processing the read image information as it is, a process for automatically optimizing the gradation by taking advantage of the conversion into digital data is performed.

This processing will be described with reference to FIGS. FIG. 6 is a density histogram obtained as a result of reading an image frame of a negative film, which is an example of an image forming medium, by image reading means such as a scanner. In this example, the image information has been read as 8-bit digital data, and has two values from 0 (darkest) to 255 (brightest).
Image information is obtained as density data having 56 gradations. In the example of FIG. 6, the ratio of the pixel having the density x to all the pixels is y%. In the example of FIG. 6, there is a peak at a portion indicated by M, and this portion indicates that there are many pixels of similar gradation. If such similar gradations are distributed in a narrow range, if this is used as it is in a photographic print, the number of pixels distributed is large, giving a sticky impression, and an image of poor quality Will be formed.

On the other hand, when attention is paid to the portion indicated by T in the density histogram, it is found that the number of pixels in this portion is considerably smaller than that in the portion indicated by M. This does not mean that a gray scale having as many as 256 levels is used effectively. Therefore, a process of smoothing a histogram is performed by effectively utilizing the advantage of converting image information into digital data. This will be described with reference to FIG.

FIG. 7 shows the density cumulative frequency distribution data obtained from the density histogram data obtained as shown in FIG. Similarly, the horizontal axis shows the density value, and the vertical axis shows the ratio (%). Then, a density histogram smoothing look-up table (hereinafter, the look-up table is sometimes referred to as LUT) shown in FIG. 8 is created from the density cumulative frequency distribution data of FIG. The curve shown in FIG. 8 is the same as the curve shown in FIG. 7, except that the vertical axis in FIG. 8 is the density value to be converted. This smoothed LU
According to T, for example, pixels having the density data of x ₃ is converted to density data of y _3.

When the image conversion processing of the image data having the density histogram shown in FIG. 6 is performed by using the smoothing LUT shown in FIG. 8, a density histogram as shown in FIG. 9 can be obtained. As is clear from FIG. 9, the density histogram is smoothed, and a wide range of gradations in a large area in the entire image as indicated by M in FIG. 6 can be used. In other words, a portion having a large area in the image is easily noticeable by human eyes, which means that gradation can be used efficiently. For example, considering a scene in which a wide blue sky appears in the background of a person, a blue sky portion having a large area in an image becomes a photograph with rich gradation and a very good appearance.

[0007]

However, according to the above example, a portion having a large area (blue sky) becomes rich and rich and the appearance is improved, but the area occupied in the image of the face of the person who is the main subject is increased. Is smaller, the gradation may be crushed. For example, as shown in FIG. 8, when the concentration of the human face in the image and ranged between x ₁ of x _2, the use of smoothing LUT of FIG. 8, the density data of x ₁ to y ₁ conversion is, the density data of x ₂ is converted to y _2. Then, the tone originally ranged from x ₁ to x ₂ is made from y ₁ is a narrower gradation range that has been converted into y _2, there is no gradation of the face of the resulting person, Nopperi It will be a confused face. That is, a portion occupying a large area in the image can be converted into an image with rich gradation by performing histogram smoothing processing.
The portion where the area occupied in the image is small, the gradation is lost, and there is a problem especially when that portion is the main subject.

The present invention has been made in view of the above circumstances, and an object of the present invention is to make it possible to make the gradation of a specific area in an image of a main subject or the like appropriate while taking advantage of the density histogram smoothing. It is to provide technology.

[0009]

To achieve the above object, an image processing apparatus according to the present invention comprises: an image reading means for reading image information from an image forming medium; and an area extracting unit for extracting a specific area from the image information. A histogram creating unit for obtaining a density histogram from the image information; a lookup table creating unit for creating a smoothing look-up table for performing smoothing of the density histogram; An image conversion processing unit for performing image conversion by an up-table, wherein the look-up table is created so that the conversion coefficient of the specific area becomes a predetermined value.

The operation of this configuration is as follows. (1) Image information is read from the image forming medium by the image reading means. (2) The specific area is extracted from the image information by the area extracting unit.
(For example, the face of a person). (3) A histogram histogram is obtained from the image information by a histogram creating unit. Note that the order of (2) and (3) may be interchanged. (4) A look-up table creating unit creates a smoothed look-up table for smoothing the histogram so that the conversion coefficient of the specific area becomes a predetermined value. (5) The image conversion processing unit performs image conversion of the read image information using the smoothing look-up table.

In other words, a predetermined conversion coefficient can be obtained for a specific area so that a predetermined gradation can be obtained. Therefore, it is possible to prevent a gradation from being lost in a specific area. Then, for a portion other than the specific region, it is possible to take advantage of the wide use of gradation by histogram smoothing. As a result, it was possible to provide an image processing apparatus capable of making the gradation of a specific region in an image of a main subject or the like appropriate while taking advantage of the density histogram smoothing.

As a preferred embodiment of the present invention, the area extracting section extracts a person's face as a specific area. With this configuration, a portion corresponding to the person's face is prevented from being grayed out. Image conversion can be performed, and while the gradation of the face of the person who is the main subject is made appropriate, image conversion that takes advantage of smoothing can be performed for the other portions.

As another preferred embodiment of the present invention, the conversion coefficient of the specific area is set to one-to-one. As a result, it is possible to perform image conversion utilizing the advantage of smoothing for the remaining portion while maintaining the gradation of the original image for the specific region.

In still another preferred embodiment of the present invention,
The density histogram is obtained from the density histogram, and the smoothed look-up table is created based on the data. According to this configuration, density cumulative frequency distribution data is created from a density histogram obtained from an original image, and a look-up table is created based on this data. Therefore, an accurate smoothing process can be performed.

An image processing method according to the present invention for achieving the object of the present invention comprises the steps of: reading image information from an image forming medium; extracting a specific area from the image information; And a step of creating a smoothing look-up table for smoothing the density histogram, and a step of performing image conversion of the read image information by the smoothing look-up table,
In the step of creating the look-up table, the look-up table is created so that the conversion coefficient of the specific area becomes a predetermined value.

The operation of this configuration is the same as that of (1) to (5) described above. Therefore, similarly, it was possible to provide an image processing method capable of making the gradation of a specific region in an image of a main subject or the like appropriate while taking advantage of the density histogram smoothing.

A photographic processing apparatus for achieving the object of the present invention is an image reading means for reading image information from a photographic film as an image forming medium, and the above description for performing image conversion on the read image information. An image processing apparatus having the above-mentioned characteristic configuration, and a printing unit for exposing the image information after the image conversion to a photosensitive material.

The operation of the photographic processing apparatus having this configuration will be described. First, image information is read from a photographic film by image reading means. Then, image conversion is performed on the image information read by the image processing device. The basic operation of this image processing device is the same as that of (2) to (5) described above. The image information after the image conversion is exposed on a photosensitive material in a printing unit. In the print photograph thus obtained, the gradation can be prevented from being destroyed by setting a predetermined conversion coefficient for a specific region, and histogram smoothing is performed for a portion other than the specific region. The advantage of using a wide range of gradations can be used. As a result, it has been possible to provide a photographic processing apparatus that can make the gradation of a specific region in an image of a main subject or the like appropriate while taking advantage of the density histogram smoothing.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an image reading apparatus and a photographic processing apparatus using the same according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating a configuration of a photographic processing apparatus.

<Description of Configuration of Photo Processing Apparatus> In FIG. 1, the photo processing apparatus includes a scanner unit P1 and a printing unit P2.
(Corresponding to a digital exposure unit), and the scanner unit P1 converts an image frame of the negative film 1, which is an example of a photographic film, into a CCD area sensor 6 (hereinafter, referred to as an area sensor and corresponds to an image reading unit). ), A mirror tunnel 3, a negative mask 4 for positioning an image frame, a reading lens 5, an area sensor 6, a roller 7 for transporting the negative film 1, and a drive motor. 8 is provided.

The printing section P2 includes a paper magazine 12 for storing paper 11 (corresponding to a photosensitive material) conveyed along a predetermined conveyance path, a conveyance roller 13 for conveying the paper 11, and a conveyance roller 13. A drive motor 14 for driving and a digital exposure head 15 for forming a digital image on the paper 11 by moving in the direction of arrow A along the transport path of the paper 11 are provided. As the digital exposure head 15, an appropriate one such as a fluorescent printer, a PLZT type printer, a CRT printer or the like can be adopted. The paper 11 on which the image is formed is subjected to processing according to the type of the paper 11, such as development processing, drying processing, and cutting processing, and is finally returned to the customer as a print.

The image processing device 20 is an area sensor.
Image conversion processing is performed on the image information of the negative film 1 read from step 6, and the details will be described later. The controller 10 controls the operation of each unit of the apparatus, including the image processing apparatus 20, and a monitor 16 and a keyboard 17 are connected.

<Configuration of Image Processing Apparatus> Next, the configuration of the image processing apparatus 20 will be described with reference to the block diagram of FIG. A /
The D converter 21 converts analog image data read by the CCD of the area sensor 6 into digital image data. The frame memory 22 stores one frame of image data. The area extracting unit 23 extracts a specific area from the image data, and in this embodiment, extracts a face of a person. A known method may be used as a method for extracting the face of a person.
If the B data has a ratio in a predetermined range, it is recognized as a face, and density data in this range is obtained.

On the other hand, the histogram creating section 24 creates a density histogram (described with reference to FIG. 6) based on the read image data. Concentration frequency distribution creation unit 25
Creates density cumulative frequency distribution data (described with reference to FIG. 7) based on the density histogram created by the histogram creating unit 24. The LUT creating unit 26 creates a density histogram smoothed LUT based on the density cumulative frequency distribution data and the face data extracted by the area extracting unit 23, and the smoothed LUT is stored in the LUT storage unit 27. . The image conversion processing unit 28 applies the density histogram smoothing LU stored in the LUT storage unit 27 to the original image data read from the frame memory 22.
Image conversion is performed by T, and the converted image data is temporarily stored in the converted image storage unit 29. Conversion image storage unit 29
For example, it is preferable that data of an image frame for one order can be stored. It is preferable that an operator checks before displaying the converted image data on the monitor 16 and performing the exposure processing.

<Processing Procedure by Image Processing Apparatus> Next, a processing procedure of image conversion by the image processing apparatus 20 will be described with reference to a flowchart of FIG. First, the negative film 1 is set on the negative mask 4 (# 01). Controller 10
The image frame of the negative film 1 is read by the area sensor 6 on the basis of the command from (# 02). The read image data is A / D converted (# 03) and stored in the frame memory 22 (# 04). Next, the face of a person is extracted by the area extracting unit 23 as a specific area in the image data (# 05). As described above, the face of a person can be extracted by a known method.

Next, a density histogram is created by the histogram creating section 24. This histogram is shown in FIG. 6 already described in the section of the prior art. 6 and 7 are used for convenience of explanation. In FIG. 6, the image data of the negative film 1 is read as 8-bit digital data, and is represented as density data (luminance data) having 256 gradations from 0 (darkest) to 255 (brightest). Information is available. For example, it is shown that the ratio of the pixel having the density x to all the pixels is y%.

From the density histogram data obtained as shown in FIG. 6, the density cumulative frequency distribution creating section 25 obtains the density cumulative frequency distribution data as shown in FIG. FIG.
In the graph, the abscissa shows the density value in the same way, and the ordinate shows the ratio
Is taking. A smoothed LUT finally obtained from the density cumulative frequency distribution data in FIG. 7 is shown in FIG. 4B, which will be described step by step. First, from the concentration cumulative frequency distribution data obtained as shown in FIG.
A density histogram smoothing LUT of the first step as shown in FIG. The horizontal axis indicates the density value x of the pixel data to be converted and the vertical axis indicates the converted density value y. This smoothing LUT is the same as that shown in FIG. 8 described in the related art.

Next, based on the area data of the human face extracted by the area extracting unit 23, the density data of the human face is represented by x _{1 in} FIG.
And those obtained as in the range of ~x _2. According to the prior art, data having a concentration of x ₁ is converted to density data of y _1, the data will have been converted into the data of y ₂ with a concentration of x _2, the gradation of x ₁ ~x ₂ The face of the person having the image has been compressed to a gray scale of y ₁ to y ₂ . Therefore, for the range of Fig. 4 (a = 64.) X ₁ as shown in (b) from (a = 128.) X _2, and one-to-one transform coefficient. That is, _{x 1 = y 1 '(=} 64) x 2 = y 2' (= 128).

In the range where the density is higher than x ₂ , y _n ′ = y ₂ + (y ₂ ′ −y ₂ ) × (x ₂₅₅ −x _n ) /
Converted by the formula (x ₂₅₅ -x _2), concentration at a range smaller than x ₁ is converted by the equation _{y n '= y 1 + (} y 1' -y 1) × x n / x 1. The density histogram smoothing LUT (second step) thus obtained is shown in FIG.
(B).

As described above, the LUT is created (# 0).
8), this LUT is stored in the LUT storage unit 27. Next, an image conversion process is performed using the created LUT (# 09). By using the LUT, image conversion can be performed at high speed. The converted image is temporarily stored in the converted image storage unit 29 (# 10). FIG. 5 shows the density histogram after image conversion. The facial part of the person's face retains the gradation of the original image, the other parts are smoothed, and the wide area in the image has wide gradation. High quality images can be obtained. It is preferable that the image after the image conversion is displayed on the monitor 16 and the operator checks the image.

Next, it is determined whether or not the image processing for one order has been completed (# 10), and if not, the process returns to step # 02. When the image processing for one order is completed,
The image data is sequentially transferred from the controller 10 to the digital exposure head 15, and the paper 11 is exposed (# 12). When the exposure is completed, the finished print is developed and dried, and the finished print is handed to the customer.

<Another Embodiment> In this embodiment, a specific area is automatically extracted. In addition, a read image is displayed on a monitor, and an operator specifies the area on the screen to extract the area. You may do it. In addition, a subject (animal, flower, building, etc.) other than a person may be extracted as the specific area.

The image reading means may be a line sensor instead of the area sensor. Further, a positive film may be used as the photographic film. Further, as the image forming medium, for example, a photographic print may be used instead of the photographic film.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a photographic processing apparatus according to an embodiment.

FIG. 2 is a functional block diagram illustrating a configuration of an image processing apparatus.

FIG. 3 is a flowchart illustrating an image conversion processing procedure in the image processing apparatus.

FIG. 4 is a diagram showing a smoothing LUT according to the embodiment;

FIG. 5 is a diagram showing a density histogram after image conversion.

FIG. 6 is a diagram showing a density histogram;

FIG. 7 is a diagram showing concentration cumulative frequency distribution data;

FIG. 8 is a density histogram smoothing LUT according to the related art.
Figure showing

FIG. 9 is a diagram showing a density histogram smoothed by a smoothing LUT according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Negative film 6 Area sensor 10 Controller 20 Image processing device 21 A / D conversion part 23 Area extraction part 24 Histogram creation part 25 Concentration cumulative frequency distribution creation part 26 LUT creation part 28 Image conversion processing part

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5B057 BA02 CE11 CH07 DA08 DC23 DC25 5C077 LL04 MP01 PP15 PQ19 PQ23 TT09 5L096 EA35 FA14 FA37 GA40 GA53 9A001 BZ03 BZ04 EZ05 HH25 HH28 JJ35 KK42

Claims (6)

[Claims] An image reading unit that reads image information from an image forming medium; an area extracting unit that extracts a specific area from the image information; a histogram creating unit that obtains a density histogram from the image information; A look-up table creating unit for creating a smoothing look-up table for performing the smoothing, and an image conversion processing unit for performing image conversion of the read image information using the smoothing look-up table. The image processing apparatus according to any one of claims 1 to 3, wherein the conversion coefficient is generated such that a conversion coefficient of the specific area is predetermined. 2. The image processing apparatus according to claim 1, wherein the area extracting unit extracts a human face as a specific area. 3. The image processing apparatus according to claim 1, wherein the conversion coefficient of the specific area is set one-to-one. 4. The method according to claim 1, wherein density cumulative frequency distribution data is obtained from the density histogram, and the smoothed look-up table is created based on the data. The image processing apparatus according to any one of the preceding claims. 5. A step of reading image information from an image forming medium, a step of extracting a specific area from the image information, a step of obtaining a density histogram from the image information, and a step of smoothing the density histogram. Creating a look-up table, and performing image conversion of the read image information using the smoothed look-up table. In the step of creating the look-up table, the conversion coefficient of the specific area is An image processing method characterized by being created so as to be predetermined. 6. An image processing apparatus according to claim 1, wherein said image reading means reads image information from a photographic film as an image forming medium, and performs image conversion on the read image information. And a printing unit for exposing the image information after the image conversion to a photosensitive material.