JP4140885B2 - Image processing apparatus, image processing method, and program - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus, an image processing method, and a program , and more specifically, an image processing apparatus capable of calculating the resolution of a document image captured from a scanner, a digital camera, or the like to improve character recognition accuracy, and an image The present invention relates to a processing method and a program .
[0002]
[Prior art]
In recent years, as the processing power of personal computers has dramatically improved and image data can be easily manipulated, a lot of image data is used in document creation in offices, and image data is very important. It has become a thing.
[0003]
Under such circumstances, there is an increasing demand for easily capturing a document at hand as an image and performing character recognition (OCR). To obtain image data, there is a method of recognizing characters by inputting a document image with a digital camera or a scanner.
[0004]
As a conventional technique for photographing a document image with a digital camera, for example, a photographing means for photographing a subject, a detecting means for detecting a distance to the subject at the time of photographing by the photographing means, and a detection means. A determination means for determining the size of the subject based on a distance to the subject and a size of a photographed image of the subject photographed by the photographing means; and a size of the subject determined by the determination means. Accordingly, there has been proposed a photographic image processing apparatus including correction output means for correcting the size of a photographic image taken by the photographic means and outputting the corrected photographic image (Japanese Patent Laid-Open No. 2001-14453). reference).
[0005]
That is, for example, when a standard format is created by a word processor, this conventional technique automatically corrects an image corresponding to the size of the standard format by photographing a document of the standard format with a digital camera. The actual size image data is acquired from the image.
[0006]
Conventionally, there has been proposed a digital camera that increases the resolution of a digital image taken with a digital camera and incorporates an OCR (character recognition) device to perform high resolution processing to increase the recognition rate (Japanese Patent Laid-Open No. 9-289624). No. publication).
[0007]
In other words, this conventional technique increases the resolution (pixel density conversion) of an image taken with a digital camera to improve the character recognition rate.
[0008]
[Problems to be solved by the invention]
However, in the technique described in the conventional publication, it is necessary to improve the character recognition rate.
[0009]
That is, in character recognition (OCR), resolution information is often required to adapt to an image.
[0010]
However, the conventional technology described in Japanese Patent Application Laid-Open No. 2001-14453 obtains actual size image data from a captured image, but the resolution is unknown, which is a problem in improving the character recognition rate.
[0011]
In the prior art described in Japanese Patent Laid-Open No. 9-289624, the resolution of a picture taken with a digital camera is increased (pixel density conversion), but the resolution accuracy such as an error is generated. There was a problem, and there was a need for improvement.
[0012]
SUMMARY An advantage of some aspects of the invention is that it provides an image processing apparatus, an image processing method, and a program for obtaining an accurate resolution of a document image captured by a digital camera or the like and improving the recognition accuracy of character recognition (OCR).
[0013]
[Means for Solving the Problems]
The image processing apparatus according to the first aspect of the present invention provides a means for estimating the resolution (first resolution) of the document image based on the character size of the document image, and the document image based on the distance to the document image. It has means for estimating the resolution (second resolution) and means for setting the average of the estimated first resolution and second resolution as the resolution of the document image.
[0014]
According to the image processing method of the present invention, the document processing apparatus estimates the resolution (first resolution) of the document image based on the character size of the document image, and based on the distance to the document image. And executing the step of estimating the resolution (second resolution) of the document image and setting the average of the estimated first resolution and second resolution as the resolution of the document image. To do.
[0015]
According to a third aspect of the present invention, there is provided a program for estimating a resolution (first resolution) of a document image based on a character size of the document image, and a resolution of the document image based on a distance to the document image ( (2nd resolution) and a program for causing a computer to execute a step of setting an average of the estimated first resolution and second resolution as the resolution of the document image. To do.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. The embodiments described below are preferred embodiments of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. As long as there is no description which limits, it is not restricted to these aspects.
[0017]
1 to 3 are diagrams for explaining a first embodiment as a premise of the present invention. FIG. 1 is a block diagram of a main part of an image processing apparatus 1 to which the first embodiment is applied. is there.
[0018]
In FIG. 1, the image processing apparatus 1 includes an input unit 2, a character size estimation unit 3, a resolution estimation unit 4, an output unit 5, and the like.
[0019]
The input unit (input unit) 2 inputs a document image, and takes in a document image obtained by photographing a subject from a silver salt photograph or a lens of a digital camera, or takes a photograph image as document image data using a scanner. , Output to the character size estimation unit 3.
[0020]
The character size estimation unit (character size estimation means) 3 extracts characters from the document image input from the input unit 2, estimates the character size, and outputs the estimated character size to the resolution estimation unit 4. The character size estimation unit 3 checks whether the data input from the input unit 2 is a document image, extracts characters only when the data is a document image, and estimates the character size.
[0021]
The resolution estimation unit (resolution estimation unit) 4 estimates the resolution based on the character size estimated by the character size estimation unit 3.
[0022]
The output unit 5 outputs display display, printout, audio, and the like, and outputs an image based on the resolution estimated by the resolution estimation unit 4.
[0023]
As shown in FIG. 2, the image processing apparatus 1 has a resolution estimation method program (resolution estimation program) recorded in a computer (information processing apparatus) 10 such as a personal computer, such as a CD (Compact Disc) or a DVD ( It is constructed by reading a predetermined recording medium 20 such as a Digital Video Disk).
[0024]
That is, the computer 10 generally includes an input I / F 11, a CPU (Central Processing Unit) 12, a drive 13, a memory 14, an output I / F 15, a network controller 16 and the like, as shown in FIG. Main parts are connected to the bus 17. The computer 10 is constructed as the image processing apparatus 1 by reading and introducing the recording medium 20 recorded with the resolution estimation program such as CD or DVD into the drive 13.
[0025]
The memory 14 uses, for example, a large-capacity storage medium such as a hard disk, and stores an OS (Operating System) on which the computer 10 operates, a necessary program, and a resolution estimation program introduced from the recording medium 20.
[0026]
The CPU 12 executes various programs on the OS in the memory 14, in particular, a resolution estimation program, and executes resolution estimation processing.
[0027]
The input I / F 11 is used for inputting various data, particularly for inputting document image data.
[0028]
The output I / F 15 is connected to a display, a printer, a speaker, a network, etc.
It is used for outputting various data, particularly for outputting document images.
[0029]
The network controller 16 is used to output data to a network (not shown) to which the computer 10 is connected.
[0030]
Next, the operation of the present embodiment will be described. The image processing apparatus 1 according to the present embodiment is characterized in that the resolution of an input document image is estimated so that character recognition (OCR) can be performed accurately.
[0031]
That is, as shown in FIG. 3, the image processing apparatus 1 first performs an image input process from the input unit 2 (step S101). In this image input processing, a silver halide photograph or a document image obtained by photographing a subject from a lens of a digital camera is captured, or a photographic image is captured as document image data using a scanner.
[0032]
When the image processing apparatus 1 captures the data, the image processing apparatus 1 checks whether the captured data is a document image (step S102). If the data is not a document image, the image processing apparatus 1 outputs the data as it is from the output unit 5 and ends the processing (step S102). Step S105). In the determination of whether or not this data is a document image and character extraction, a function used in a generally known character recognition (OCR) process can be used.
[0033]
If the captured data is a document image in step S102, the character size estimation unit 3 estimates the character size and outputs it to the resolution estimation unit 4 (step S103), and the resolution estimation unit 4 estimates the resolution (step S103). S104).
[0034]
In order to estimate the character size from the input document image, the following method can be used.
[0035]
That is, when the estimated character size (pixel) is v, a predetermined constant (dpi / pixel) is N, and the estimated resolution (dpi) is R1, the character size (pixel) v is obtained. The image is binarized to obtain a connected portion, and a horizontal / vertical size histogram is obtained to obtain a value giving the maximum frequency. N is a constant, which is determined for each image processing apparatus 1.
[0036]
The estimated resolution R1 is obtained as follows using the character size v obtained in step S103.
[0037]
For example, when N = 200/64 (dpi / pixel) and the character size v is v = 32 (pixel), the estimated resolution R1 is R1 = 200/64 × 32, R1 = 100 (dpi) It becomes.
[0038]
Thereafter, the image processing apparatus 1 outputs the resolution information to the output unit 5 for display display, printout, audio, or the like, or is incorporated into the additional information part of the image to output the display display, printout, audio, etc. 5 to finish the process (step S105).
[0039]
As described above, the image processing apparatus 1 according to the present embodiment starts from the document image input from the input unit 2.
The character size estimation unit 3 estimates the character size of the document image, and the resolution can be calculated easily and accurately based on the estimated character size based on the character size of the document image. Accuracy can be improved.
[0040]
4 to 6 are diagrams for explaining a second embodiment as a premise of the present invention, and FIG. 4 is a block diagram of a main part of an image processing apparatus 30 to which the second embodiment is applied. It is.
[0041]
In the description of the present embodiment, the same components as those of the image processing apparatus 1 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
[0042]
In FIG. 4, the image processing device 30 includes an input unit 2, a resolution estimation unit 4, and an output unit 5 similar to those of the image processing device 1 of the first embodiment, and also includes a distance estimation unit 31. The character size estimation unit 3 of the image processing apparatus 1 according to the first embodiment is not provided.
[0043]
The distance estimation unit (distance estimation unit) 31 estimates the distance from the input unit 2 to the document image and outputs the estimated distance to the resolution estimation unit 4.
[0044]
The resolution estimation unit 4 estimates the resolution of the image based on the estimated distance.
[0045]
As shown in FIG. 5, the image processing apparatus 30 according to the present embodiment first performs an image input process from the input unit 2 (step S201). In this image input processing, as in the case of the first embodiment, a document image obtained by photographing a subject from a silver halide photograph or a lens of a digital camera is captured, or a photographic image is captured as document image data using a scanner. .
[0046]
When the image processing apparatus 30 captures the data, the image processing apparatus 30 checks whether the captured data is a document image (step S202). If the data is not a document image, the image processing apparatus 30 outputs the data as it is from the output unit 5 and ends the processing (step S202). Step S205). In the determination of whether or not this data is a document image and character extraction, a function used in a generally known character recognition (OCR) process can be used as described above.
[0047]
If the captured data is a document image in step S202, the distance estimation unit 31 estimates the distance from the input unit 2 to the document image, and outputs it to the resolution estimation unit 4 (step S203). Estimates the resolution (step S204).
[0048]
In order to estimate the resolution from the input document image, the following method can be used.
[0049]
That is, as shown in FIG. 6, the estimated distance (m) to the document image that is the input image is l, the predetermined constant (dpi / pixel) is C, the estimated resolution (dpi) is R2 When the distance (m) l is obtained by actually measuring the distance to the input image, and the resolution at the distance r to the virtual image is 200 dpi, r: 200 (dpi) = 1 (m): R2 (dpi), R2 = (200 / r) × l.
[0050]
At this time, 200 / r is a constant C. This constant C is determined for each resolution estimation device 30.
[0051]
The image processing apparatus 30 then outputs the resolution information to the output unit 5 for display display, printout, audio, or the like, or is incorporated into the additional information portion of the image and output unit for display display, printout, audio, etc. 5 to finish the processing (step S205).
[0052]
As described above, the image processing apparatus 30 according to the present embodiment estimates the distance from the document image input from the input unit 2 to the document image by the distance estimation unit 31, and estimates the resolution based on the estimated distance. Part 4 estimates the resolution of the document image.
[0053]
Therefore, the resolution can be calculated easily and accurately based on the distance to the document image, and the character recognition accuracy of the document image can be improved.
[0054]
FIGS. 7 and 8 are diagrams for explaining a third embodiment of the present invention. FIG. 7 is a block diagram of a main part of an image processing apparatus 40 to which the third embodiment is applied. .
[0055]
This embodiment is a combination of the first embodiment and the second embodiment. Also in the description of the present embodiment , the same components as those of the image processing apparatus 1 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
[0056]
In FIG. 7, an image processing device 40 includes an input unit 2, a resolution estimation unit 4, and an output unit 5 similar to the resolution estimation device 1 of the first embodiment, and a character size / distance estimation unit 41. It has.
[0057]
The character size / distance estimation unit 41 includes a character size estimation unit 42 and a distance estimation unit 43.
[0058]
The character size estimation unit (character size estimation means) 42 extracts characters from the document image input from the input unit 2 and estimates the character size in the same manner as the character size estimation unit 3 of the first embodiment. And output to the resolution estimation unit 4. The character size estimation unit 42 checks whether the data input from the input unit 2 is a document image, extracts a character only when the data is a document image, and estimates the character size.
[0059]
The distance estimation unit (distance estimation unit) 43 estimates the distance from the input unit 2 to the document image, and outputs the estimated distance to the resolution estimation unit 4, similarly to the distance estimation unit 31 of the second embodiment.
[0060]
As shown in FIG. 8, the image processing apparatus 40 according to the present embodiment first performs image input processing from the input unit 2 (step S301). In this image input processing, as in the case of the first embodiment, a document image obtained by photographing a subject from a silver halide photograph or a lens of a digital camera is captured, or a photographic image is captured as document image data using a scanner. .
[0061]
When the image processing apparatus 40 captures the data, the image processing apparatus 40 checks whether the captured data is a document image (step S302). If the data is not a document image, the image processing apparatus 40 outputs the data as it is and ends the processing (step S306). In the determination of whether or not this data is a document image and character extraction, a function used in a generally known character recognition (OCR) process can be used as described above.
[0062]
If the captured data is a document image in step S302, first, the character size estimation unit 42 of the character size / distance estimation unit 41 performs a character size estimation process as in the case of the first embodiment. The character size is estimated and output to the resolution estimator 4 (step S303). Next, the distance estimator 43 performs the distance estimation process as in the case of the second embodiment, and inputs it. The distance from the unit 2 to the document image is estimated and output to the resolution estimation unit 4 (step S304). Then, the resolution estimation unit 4 estimates the resolution based on the character size and distance (step S305). At this time, the resolution estimation unit 4 calculates the resolution R1 from the character size in step S303 as in the case of the first embodiment, and the second embodiment from the distance in step S304. As in the case of, the resolution R2 is calculated, and the final resolution R3 is calculated as follows using these two resolutions R1 and R2.
R3 = (R1 + R2) / 2
[0063]
The image processing apparatus 40 then outputs the resolution information to the output unit 5 for display display, printout, audio, or the like, or is incorporated into the additional information portion of the image and output unit for display display, printout, audio, etc. 5 to finish the process (step S306).
[0064]
As described above, the image processing apparatus 40 according to the present embodiment estimates the character size of the document image from the document image input from the input unit 2 by the character size estimation unit 42 of the character size / distance estimation unit 41. The distance to the document image is estimated by the distance estimating unit 43 of the character size / distance estimating unit 41, and the resolution of the document image is estimated by the resolution estimating unit 4 based on the estimated character size and distance. .
[0065]
Therefore, the resolution can be calculated easily and more accurately based on the character size of the document image and the distance to the document image, and the character recognition accuracy of the document image can be further improved.
[0066]
FIG. 9 is a block diagram of a main part of a digital camera 50 to which the image processing apparatus according to the embodiment of the present invention is applied.
[0067]
In FIG. 9, the digital camera 50 includes an input I / F 51, a CPU 52, a memory 53, a drive 54, a network controller 55, an output I / F 56, and the like.
[0068]
The drive 54 is a large-capacity storage medium serving as a main storage, and the digital camera is read by introducing a recording medium 60 recorded with a resolution estimation program such as a CD or a DVD into the large-capacity storage medium. 50 can be constructed as a digital camera incorporating an image processing device .
[0069]
The input I / F 51 is an interface for inputting an image. The CPU 52 controls each part of the digital camera 50 based on a program of the drive 54 to operate as the digital camera 50 and is installed in the drive 54. The resolution estimation process is executed by the resolution estimation program.
[0070]
The memory 53 is an auxiliary storage medium for storing image data and the like, and the network controller 55 is connected to the network and exchanges data with devices on the network. The output I / F 56 is an interface for outputting image data.
[0071]
In the present embodiment, as shown in FIG. 10, the digital camera 50 is set so that the subject 71 is automatically photographed in the sentence image mode.
[0072]
The digital camera 50 measures the distance to the subject 71 and extracts the contour of the subject 71 and the like. For this contour extraction, a generally known contour extraction algorithm such as character recognition (OCR) is used.
[0073]
Next, in the digital camera 50, the CPU 52 calculates the resolution using the storage medium of the memory 53 and the drive 54, and outputs the estimated value of the calculated resolution as an image file 72 from the output I / F 56.
[0074]
As described above, the digital camera 50 according to the present embodiment implements a function as an image processing apparatus that executes a resolution estimation process by installing a resolution estimation program in the digital camera 50 capable of capturing a document image. .
[0075]
Therefore, a document image can be photographed with the digital camera 50, and the resolution of the photographed document image can be calculated easily and accurately, and the character recognition accuracy of the document image can be improved.
[0076]
In each of the above embodiments, a resolution estimation program for estimating the resolution of the input image is recorded in the recording media 20 and 60, and the resolution estimation program for the recording media 20 and 60 is stored in an information processing apparatus such as the computer 10 or the like. By mounting on the digital camera 50, the digital camera 50 that executes resolution estimation processing is constructed.
[0077]
Therefore, it is possible to easily construct the image processing apparatus and the digital camera 50 that executes the resolution estimation method for calculating the resolution of the document image easily and accurately and further improving the character recognition accuracy of the document image.
[0078]
The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above, and various modifications can be made without departing from the scope of the invention. Needless to say.
[0079]
【The invention's effect】
According to the present invention, the resolution of a document image can be calculated easily and more accurately based on the character size of the document image and the distance to the document image, and the character recognition accuracy of the document image can be further improved. Can do.
[Brief description of the drawings]
FIG. 1 is a block diagram of a main part of an image processing apparatus to which a first embodiment of the present invention is applied .
FIG. 2 is a block diagram of a main part of a computer to which the image processing apparatus of FIG. 1 is applied.
FIG. 3 is a flowchart showing resolution estimation processing by the image processing apparatus of FIG. 1;
FIG. 4 is a block diagram of a main part of an image processing apparatus to which a second embodiment on the premise of the present invention is applied .
FIG. 5 is a flowchart showing resolution estimation processing by the image processing apparatus of FIG. 4;
6 is an explanatory diagram of distance estimation processing by the image processing apparatus of FIG. 4;
FIG. 7 is a block diagram of a main part of an image processing apparatus to which a third embodiment of the present invention is applied .
8 is a flowchart showing resolution estimation processing by the image processing apparatus in FIG. 7;
FIG. 9 is a block diagram of the main part of a digital camera to which the image processing apparatus of the present invention is applied.
10 is an explanatory diagram of resolution estimation processing by the digital camera of FIG. 9;
[Explanation of symbols]
1 image processing device 2 input unit 3 character size estimation unit 4 resolution estimation unit 5 output unit 10 computer 11 input I / F
12 CPU
13 Drive 14 Memory 15 Output I / F
16 Network controller 17 Bus 20 Recording medium 30 Image processing device 31 Distance estimation unit 40 Image processing device 41 Character size / distance estimation unit 42 Character size estimation unit 43 Distance estimation unit 50 Digital camera 51 Input I / F
52 CPU
53 Memory 54 Drive 55 Network controller 56 Output I / F
60 Recording medium 71 Subject 72 Image file

Claims (3)

Means for estimating the resolution of the document image (hereinafter, first resolution) based on the character size of the document image;
Means for estimating a resolution of the document image (hereinafter, second resolution) based on a distance to the document image;
Means for taking the average of the estimated first resolution and second resolution as the resolution of the document image;
An image processing apparatus comprising: The document processing device
Estimating the resolution of the document image (hereinafter, first resolution) based on the character size of the document image;
Estimating a resolution of the document image (hereinafter referred to as a second resolution) based on a distance to the document image;
Taking the average of the estimated first resolution and second resolution as the resolution of the document image;
The image processing method characterized by performing. Estimating the resolution of the document image (hereinafter, first resolution) based on the character size of the document image;
Estimating a resolution of the document image (hereinafter referred to as a second resolution) based on a distance to the document image;
Taking the average of the estimated first resolution and second resolution as the resolution of the document image;
A program that causes a computer to execute.

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