JP2007114828A - Image processing apparatus and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To read indicated value by using an image of a round type instrument picked up by a camera set up on site without initializing the instrument beforehand. <P>SOLUTION: An original image of the round type instrument 2 is inputted into an image inputting section 11. An instrument structure learning section 12 determines the positions of numerals meaning the scale markings of the round type instrument 2 represented in the original image, and stores the determined position information of the numerals. The instrument structure learning section 12 determines the positions of an indicator in the original image. An indicator value calculating section 13 calculates the numeric value corresponding to the position of the indicator as the indicator value, based on the position information of the indicator determined by the instrument structure learning section 12 and the position information of the numerals. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing technique, and more particularly to an image processing apparatus and an image processing method for processing an image of a round instrument and calculating an instruction value indicated by a pointer of the round instrument.

  Instruments such as analog meters are widely used for measuring and monitoring various systems. In recent years, automation of factories and cost reduction have been desired, and automation of inspection with a meter has been attempted. Methods for automating inspections with meters include meter replacement, meter modification, and automated visual inspection. Of these, replacement or modification of the meter has a serious problem that it is costly, visibility is deteriorated, and the system must be stopped during the replacement period. On the other hand, the automation of the visual recognition work has the advantage that it is only necessary to install a camera and an image input device and does not require a system stop. Further, since the meter does not come into contact with the meter, visibility can be maintained, difficult high places and dangerous areas can be inspected, and temporary automatic monitoring can be easily performed. From this point of view, it is expected to automate the visual recognition work of analog meters by image processing, particularly round meters that occupy most of analog meters.

  A processing flow of a general analog meter automatic reading system is shown in FIG. A meter to be inspected is photographed with the installed camera (step S100), the image is analyzed (step S101), and an instruction value is output (step S102). The inspection result can be stored or analyzed (step S103).

  When reading the indicated value of the instrument using the image, the structure information of the instrument is required. Here, the structure information is information necessary for reading the instruction value. In a conventional system, prior information necessary for reading an instruction value is set in the system by attaching a marker or the like when the system is installed. Specifically, a reference position in image analysis is set by placing a marker on the display panel of the instrument, and information on the set reference position is used when reading an instruction value. In this way, information necessary for reading is given in advance as an initial setting.

In addition, as an example of the prior art relating to image recognition, for example, Patent Document 1 below describes an image recognition method in which a predetermined mark is extracted from a binary image and an indicator needle is read based on the extracted mark.
JP 2001-22433 A

  However, in the system that requires the initial setting as described above, the reading value of the instrument cannot be read if the prior information necessary for reading the reading value is not set. Moreover, attaching prior information such as markers to the display panels of all the instruments existing in large numbers in the factory is excessive in labor and cost.

  Therefore, the present invention solves the above-mentioned problems of the prior art, and does not require prior initial setting, and reads the indicated value using only the image of the round instrument photographed with the camera installed at the site. An object is to provide an image processing apparatus and an image processing method.

  In order to solve the above problems, the present invention is an image processing apparatus for processing an image of a round instrument photographed by an image photographing means and calculating an instruction value indicated by a pointer of the round instrument, Image input means for inputting an image of a round instrument, display panel area extracting means for extracting a display panel area of the round instrument from the inputted image of the round instrument, and vertical from the center of the display panel area A reference line determining means for determining a straight line drawn in the lower direction as a reference line, and extracting a center line of the pointer of the round instrument from the extracted display panel area, and extracting the center line of the extracted pointer and the reference A pointer position determining means for determining an angle formed by a line as the position of the pointer, a scale area that is an area where the scale is present, and a number indicating a numerical value of the scale are described. Number area that is an area An area dividing unit that divides the center of the display panel area and a center / pointer area that is a combined area of the pointers, a number recognition unit that recognizes by cutting out numbers from the number areas, and a center of the display panel area Number position determining / accumulating means for determining the angle formed by the straight line drawn from the center of gravity of each recognized number from the reference line and the reference line as the position of each number and storing it in association with each number And an instruction value calculation means for calculating an instruction value indicated by the pointer based on the determined position information of the pointer and the accumulated position information of each numeral.

  Further, the present invention provides the image processing apparatus, further comprising rearranging the position information of each numeral stored in the numeral position determining / accumulating unit in ascending or descending order with respect to an angle corresponding to each numeral. In the digit string to be obtained, a numeric position correcting means for detecting an error in the position of each numeral from the magnitude relationship with adjacent numerals and correcting the position information of each numeral is provided.

  In the image processing apparatus according to the present invention, the numeral position correcting unit further associates each recognized numeral with a scale included in the scale area and stores the number in the numeral position determining / accumulating unit. The angle corresponding to each of the numbers is changed to an angle formed by a straight line drawn from the center of the display panel area with respect to the scale associated with the numbers and the reference line.

  In the image processing apparatus according to the present invention, the image processing apparatus further includes distortion correction means for correcting image distortion in the display board area of the round instrument extracted by the display board area extraction means.

  The present invention is also an image processing method for processing an image of a round instrument photographed by an image photographing means and calculating an indication value indicated by a pointer of the round instrument, wherein the image of the round instrument is An image input step for inputting a display panel, a display panel area extraction step for extracting a display panel area of the round instrument from the input image of the round instrument, and a vertical pull down from the center of the display panel area A reference line determining step for determining a straight line as a reference line, and a center line of the pointer of the round instrument is extracted from the extracted display panel area, and an angle formed by the center line of the extracted pointer and the reference line A pointer position determining step for determining the position of the pointer, a scale area that is an area where a scale exists, and a number area that is a number area indicating a numerical value of the scale. An area dividing step for dividing the center of the display board area and a center / pointer area which is a combined area of the pointers, a number recognition step for extracting and recognizing numbers from the number areas, and a center of the display board area Determine the angle formed by the straight line drawn with respect to the center of gravity of each recognized number and the reference line as the position of each number, and determine the number position to be stored in the storage means in association with each number -An accumulation step; and an instruction value calculation step for calculating an instruction value indicated by the pointer based on the determined position information of the pointer and the accumulated position information of each numeral. To do.

  Further, the present invention provides the image processing method, further comprising: ascending or descending order of the position information of each numeral stored in the storage means in the numeral position determining / accumulating step with respect to an angle corresponding to each numeral. In the digit string obtained by rearranging the numbers, a number position correcting step is performed in which an error in the position of each number is detected from the magnitude relationship with adjacent numbers, and the position information of each number is corrected.

  In the image processing method according to the present invention, in the image processing method, the numerical position correction step further associates each recognized number with a scale included in the scale area, and stores the stored in the storage unit. The angle corresponding to each number is changed to an angle formed by a straight line drawn from the center of the display panel area with respect to the scale associated with each number and the reference line.

  Further, the present invention is characterized in that the image processing method further includes a distortion correction step of correcting distortion of the image of the display panel area of the round instrument extracted by the display panel area extraction step.

  According to the present invention, it is possible to automatically understand the structure of the round instrument by learning using only the image of the round instrument photographed by the camera installed in the field without the need for prior initial setting. Can be read.

  FIG. 1 is a diagram showing an example of the configuration of the present invention. The image processing device 1 is a processing device that processes an image of the round instrument 2 photographed by the camera 3 and calculates an instruction value indicated by a pointer of the round instrument 2.

  The image processing apparatus 1 includes an image input unit 11, an instrument structure learning unit 12, and an instruction value calculation unit 13. An image (original image) of the round meter 2 photographed by the camera 3 is input to the image input unit 11. The instrument structure learning unit 12 learns (automatically determines) the instrument structure of the round instrument 2 necessary for reading the indication value of the round instrument 2 based on the input image information. Specifically, the instrument structure learning unit 12 determines the position of a number indicating the numerical value of the scale of the round instrument 2 described in the input original image, and accumulates the position information of the determined number. . The instrument structure learning unit 12 determines the position of the pointer in the original image.

  The instruction value calculation unit 13 calculates an instruction value indicated by the pointer of the round instrument 2 based on the learned instrument structure. Specifically, a numerical value corresponding to the position of the pointer is calculated as an instruction value based on the position information of the pointer determined by the instrument structure learning unit 12 and the numerical position information of the round instrument 2.

  The instrument structure learning unit 12 includes a display panel region extracting unit 121, a region dividing unit 122, a reference line determining unit 123, a pointer position determining unit 124, a number recognizing unit 125, a number position determining / accumulating unit 126, and a number position correcting unit 127. Prepare.

  The display panel area extracting means 121 extracts the area of the display panel from the input original image of the round instrument 2. The area dividing means 122 has a display board area, a scale area that is an area where a scale exists, a center / pointer area that is a combination of the center of the display board and a pointer, and a number indicating a numerical value of the scale. Divide into numeric areas that are areas.

  The reference line determination unit 123 determines a reference line that is a reference line for the positions of the numbers written in the display panel area. The reference line determination unit 123 uses, for example, a straight line drawn vertically downward from the center of the display panel area as the reference line.

  The pointer position determining unit 124 extracts the center line of the pointer of the round instrument 2 from the image of the display panel area extracted by the display panel area extracting unit 121, and determines the position of the pointer.

  The number recognizing means 125 recognizes a number existing in the number area. The numeric position determining / accumulating means 126 determines the position of the recognized numeral with reference to the reference line, and accumulates the positional information of the determined numeral. The numeral position determining / accumulating means 126 determines, for example, an angle formed by a straight line drawn from the center of the display panel area with respect to the center of the numeral and a reference line as the position of the numeral.

  The numerical position correcting means 127 corrects the numerical position information stored in the numerical position determining / accumulating means 126. Specific processing of the numeric position correcting means 127 will be described later.

  Although not shown here, in the present invention, the instrument structure learning unit 12 enlarges the image of the display board area extracted by the display board area extraction means 121 at a vertical and horizontal unequal magnification, for example, and distorts the display board area. It is also possible to adopt a configuration including a module for performing the correction.

  In addition, the instrument structure learning unit 12 can be configured to include a module that creates an image from which the pointer is removed using a plurality of input original images, as will be described later. In the embodiment of the present invention, by recognizing numbers using an image from which the hands have been removed, it is possible to recognize the numbers hidden behind the hands.

  FIG. 2 is a diagram showing an example of the instruction value calculation processing flow of the present invention. First, an image (original image) of the round meter 2 taken by the camera 3 is input to the image input unit 11 (step S1).

  Next, the instrument structure learning unit 12 learns the instrument structure based on the original image (step S2). For example, the instrument structure learning unit 12 accumulates position information of numbers written in the original image with reference to the reference line. The instrument structure learning unit 12 determines the position of the pointer in the original image.

  Next, the instruction value calculation unit 13 calculates the instruction value indicated by the pointer based on the learned instrument structure (step S3). Specifically, the instruction value calculation unit 13 calculates a numerical value corresponding to the position of the pointer based on the position information of the numeral written in the original image and the position information of the pointer in the original image. Calculate as the indicated value.

(Explanation of instrument structure learning process)
The round gauge 2 indicates the indicated value as the pointer rotates. In order to read the indication value of the round instrument 2, first, information regarding the position of the pointer is required, and further, position information of a number indicating a numerical value of the scale is required.

  Hereinafter, a process of determining the position of the pointer and the position of the number from the original image of the round instrument 2 by the instrument structure learning unit 12 will be described.

  The round instrument 2 has a circular display panel. The relationship between the angle of the pointer and the indicated value is learned based on the relative position of the number written on the display panel with respect to the center of the circle. More specifically, the instrument structure learning unit 12 uses a straight line drawn vertically downward from the center of the display panel of the round instrument 2 as a reference line, and draws it from the center of the display panel with respect to the center of gravity of each number. The angle formed by the straight line and the reference line is determined as the position of each number and stored.

(1) Extraction of display panel area The display panel area extraction means 121 of the instrument structure learning unit 12 uses the input original image of the round instrument 2 shown in FIG. The circle that is the outline of is extracted. For example, an edge is extracted from the original image by a Sobel filter, and an image as shown in FIG. A binarization process is performed on the image from which the edge is extracted, and a portion having a strong edge is cut out. Then, a thinning process is performed on the binarized image as shown in FIG. 4B, and the line width of the contour line is set to one pixel, so that the display as shown in FIG. The outline 100 of the board area is extracted. Then, based on the extracted image of the contour line 100 of the display board area, a circular virtual contour line 101 as shown in FIG. 4D is created by, for example, Hough transform. Then, of the entire area of the original image, the area inside the created virtual contour 101 is set as the display board area. FIG. 3B shows an example of the display board area (the portion in the center circle in the figure).

(2) Determination of reference line The reference line determination means 123 uses, for example, a straight line drawn vertically downward from the center of a circular display panel area as a reference line. Of course, in the present invention, the reference line is not limited to a straight line drawn vertically downward from the center of the display panel area.

(3) Determination of the position of the pointer The pointer has a strong contrast with the surrounding background, and the color is black with respect to the white background. Using this feature, the position of the pointer is determined.

For example, the pointer position determining unit 124 measures the strength of the black pixel in each direction (radially) from the center of the display board area with respect to the display board area as shown in FIG. The angle formed by the straight line in the maximum direction and the reference line is defined as the pointer angle. For example, the intensity S _black of the black pixel is expressed by S _black = I _MAX −I (x, y), where the difference between the maximum luminance value I _MAX and the luminance value I (x, y) is obtained. The intensity of the black pixels of all the pixels in the display panel area is calculated, and the intensity of the black pixels existing at each angle formed by the reference line and the straight line drawn from the center of the display panel area with respect to each pixel. By taking the sum, the strength of the black pixel for each angle can be calculated.

  FIG. 5 shows an example of a black pixel intensity histogram for each angle. In this histogram, the peak portion corresponding to the angle θ where the sum of the black pixels is the strongest represents the position of the pointer. Therefore, a straight line drawn in the direction of the angle θ from the center of the display panel is used as the center line of the pointer. The angle θ is determined as the position of the pointer.

(4) Area division The display panel area includes scales, numbers, and pointers. Dividing these existing areas leads to higher processing efficiency and higher accuracy. Therefore, if the display board area is denoted by R, the area dividing means 122 divides the display board area R into a scale area R _S , a numeric area R _N , and a center / pointer area R _C (R = R _S ∪R). _N ∪R _C ). The scale area is an area where a scale exists. The number area is an area where numbers indicating scale values are written, and is an area inside the scale area. The center / pointer area is an area where the center of the display panel and the pointer exist.

  For example, in the scale area extraction, line components are extracted by performing a smoothing process, an edge extraction process, and a binarization process on the image of the display board area. Extract. The area of the outer periphery of the extracted circle is a scale area. FIG. 6A shows an example of the extracted scale area.

Next, the area R _N ∪R _C inside the circle extracted in the scale area extraction process is divided into a numerical area and a center / pointer area. Here, the region R _N ∪R _C is divided into a portion where the center of the display panel region and the pointer exist and a portion other than that by the threshold processing for the luminance value of the pixel. That is, of the areas where the luminance value of the pixel is equal to or less than the threshold value, the area overlapping the center line of the pointer is set as the center / pointer area. The number itself has a luminance value equal to or less than the threshold value, but is excluded from the center / pointer area because it does not overlap the center line of the pointer.

FIG. 6C shows an example of the center / pointer area. In the figure, a straight line OX drawn in the center / pointer region is the centerline of the pointer. Of the region R _N ∪R _C, the region other than the center / pointer region is a numeric region. FIG. 6B shows an example of a numeric area.

(5) Number position determination The position of a number is determined with reference to the reference line, and the position information of the determined number is stored. Thereafter, the number and the scale are associated with each other, and the positional deviation between the number and the scale is corrected.

  FIG. 7 shows an example of a numerical position determination process flow. First, the number recognition means 125 cuts out a number from the number area (step S11). The extraction of numbers is performed by threshold processing. An example of improving threshold processing will be described later. A rectangle containing the object cut out by the threshold processing is cut out as a number rectangle. FIG. 8A shows an example of a number rectangle to be cut out. FIG. 8A shows a number rectangle for the number “5” and a number rectangle for the number “0” surrounded by a solid line.

  Next, the number recognition means 125 recognizes the cut out number (step S12). That is, the cut-out rectangular numeral rectangle is subjected to the numeral recognition process. Here, since objects to be cut out include symbols such as units and numbers other than characters, numbers 0 to 9 are identified, and at the same time, other than numbers are rejected.

The number recognizing means 125 integrates the adjacent ones of the number rectangles containing the numbers recognized as numbers, and recognizes them as a multi-digit number (step S13). For example, the number rectangles are integrated when the number rectangles for the two recognized numbers satisfy the following three conditions.
Condition 1: The difference in the vertical size of the number rectangle is a certain value or less.
Condition 2: The horizontal interval of the number rectangle is a certain value or less.
Condition 3: The vertical displacement of the number rectangle is less than a certain value.

  As a result of the process in step S13, for example, in FIG. 8A, the number rectangle for the number “5” surrounded by the solid line and the number rectangle for the number “0” are shown in the portion surrounded by the dotted line. Integrated. As a result of the number recognition processing for the integrated number rectangle, the number “50” as shown in FIG. 8B is recognized.

  Next, the numeral position determining / accumulating means 126 determines the position of the recognized numeral (step S14).

The process of step S14 will be described with reference to FIG. The circle shown in FIG. 9 is a boundary line between the number area and the scale area, and the point O is a point indicating the center of the display board area. A straight line OA ₀ is a reference line extending vertically downward from O. Each of V _{1 to} V ₄ is a recognized single digit or a plurality of integrated digits written in the numeric area, and corresponds to each digit in the figure. A number rectangle is shown. In the figure, a straight line OA _i (1 ≦ i ≦ 4) is a straight line passing through the center of gravity of each number V _i .

Digit position determining and storing means 126, each digit rectangular, clockwise direction with respect to the reference line angle a _i, determined as the position of each number V _i, as shown in FIG. 10 (A), V _i and a the correspondence information between _i, accumulates as positional information of each number V _i.

For example, the angle a _{1 with} respect to the reference line of the number rectangle for the number V ₁ is an angle formed by the straight line OA ₁ and the reference line OA ₀ in FIG. Similarly, the angle a ₂ digit rectangular with respect to the reference line for numeral V ₂ is the angle formed by the straight line OA ₂ and the reference line OA _0, the angle a ₃ for the digits rectangular reference line for numeral V ₃ linearly OA ₃ and the reference line OA ₀ and is an angle, the angle a ₄ for the digits rectangular reference line for numeral V ₄ is the angle between the straight line OA ₄ and the reference line OA _0.

  Next, the numerical position correcting means 127 detects an error in the numerical position (step S15) and deletes the position information of the erroneous numerical position. In general, there are no guarantees that all numbers will be correctly recognized because the numbers on the instrument may be affected by lighting or the pointer may overlap the number. Here, in general, the scale numbers have a monotonically increasing property. Here, by using this property, a number that is missing a part of a plurality of digits or a number that may be erroneously recognized is detected and rejected. Specifically, a recognition error is detected from a magnitude relationship with an adjacent number in a number string obtained by rearranging the number position information stored in the number position determining / accumulating unit 126 in the order of angles.

For example, the numeric position correcting unit 127 reads the numeric position information stored in the numeric position determining / accumulating unit 126 and rearranges the numbers V _i in ascending order with respect to the angle a _i . For example, if a ₁ <a ₂ <a ₃ <a ₄ , for example, data after rearrangement of numbers as shown in FIG. 10B is created. Here, for example, when V ₃ <V ₂ , V ₃ is an error and the position information for the number V ₃ is deleted. FIG. 10C shows an example of the position information of each number after the position information of the wrong number is deleted.

The numerical position correcting means 127 reads out the numerical position information stored in the numerical position determining / accumulating means 126, and in the numerical sequence rearranged in descending order with respect to the angle a _i , an error occurs due to the magnitude relationship with the adjacent numbers. May be detected.

Finally, the numeral position correcting means 127 corrects the deviation of the numeral position by associating each numeral with the scale (step S16). In the embodiment of the present invention, for example, the angle formed by the straight line OA _i drawn from the center O shown in FIG. 9 with respect to the center of gravity of each numeral and the reference line OA ₀ is determined as the position of each numeral. An error may occur between the position of each numeral and the position of the scale corresponding to the numerical value indicated by each numeral. For example, in the original image shown in FIG. 11A, the tip of the arrow 102 drawn from the center O of the display panel area of the round instrument 2 and passing through the center of gravity of the numeral “200” is a numerical value indicated by the numeral “200”. And the position of the scale 103 surrounded by a thick dotted line may be shifted.

Accordingly, the numeral position correcting means 127 changes the angle of the straight line drawn from the center O in the direction of the center of gravity of the numeral V _i within a range of ± 5 °, and cuts out the scale 103 existing within the range. As a result of the cutout of the scale 103, for example, the scale 103 surrounded by a dotted line is cut out from the image of the scale area shown in FIG. 11B extracted from the original image in FIG.

Then, the numeral position correcting means 127 changes the angle a _i corresponding to the numeral V _i to an angle formed by a straight line drawn with respect to the scale 103 cut out from the center O and the reference line.

  In addition, for example, when the scale cannot be extracted in the cutout of the scale, it is possible to adopt a configuration in which the correction of the displacement of the numerical position is not performed.

(Explanation of instruction value calculation)
The instruction value calculation unit 13 stores the pointer position information determined by the pointer position determination unit 124, that is, information on the angle formed by the center line of the pointer and the reference line, and the number position determination / accumulation unit 126. Based on the position information of each numeral, the indicated value indicated by the pointer of the round meter 2 is calculated.

  The indicated value is obtained as follows. As the angle formed by the center line of the pointer and the reference line increases, the indicated value also increases. Further, when the scale is equally spaced, the angle and the indicated value are proportional. From this relationship, the indication value V (θ) when the angle formed by the center line of the pointer and the reference line is the angle θ is calculated by the following equation.

θ _L and θ _R respectively represent the left adjacent angle and the right adjacent angle closest to θ among the angle information stored in the numerical position determining / accumulating unit 126.

  For example, it is assumed that numerical position information as shown in FIG. 12 is stored in the numerical position determining / accumulating means 126. Here, when the angle θ of the pointer is, for example, 91 °, the instruction value is obtained as follows.

From the numerical position information shown in FIG. 12, the angles θ _L = 56 ° and θ _R = 196 °. The number V (56) = 0 and the number V (196) = 400.

  Therefore, the instruction value V (91) is

Thus, the instruction value “100” is calculated.

(Improved number recognition process)
Below, the example of improvement of the number recognition process in embodiment of this invention is demonstrated. For example, due to the reflection of strong light striking the round instrument 2, some of the numbers written on the display panel of the round instrument 2 may not be cut out or read. In some cases, the number cannot be read because the number overlaps the pointer. Therefore, in the embodiment of the present invention, the following measures are taken for numbers that are difficult to cut out and read due to the influence of illumination and guidelines.

(A) Measures against reflection of light In the embodiment of the present invention, as will be described below, the number recognition unit 125 uses a combination of dynamic threshold processing and fixed threshold processing to cut out numbers from a number area. .

  Threshold processing is used to cut out numbers in the number area. A change in brightness is observed on the display panel of the round instrument 2 due to the influence of illumination or the like. For example, on the right side in the original image shown in FIG. 13A, a white region having a high luminance value due to light reflection is seen. For this reason, if a single threshold value is used for a number area, the number may not be cut out correctly.

  In the embodiment of the present invention, by combining the results of the two threshold processings, it is possible to cut out numbers that are robust against the influence of illumination. With reference to FIG. 13 or FIG. 14, the number cut-out process will be described. First, a pre-process for removing the influence of strong light reflection or the like is applied to the numeric area. In general, an area where light is reflected has a high luminance value, and pixels in the number have a relatively low luminance value. In the preprocessing, the luminance value of a pixel that is equal to or higher than the average value of the luminance values in the number area is replaced with this average value. By such processing, it is possible to suppress the influence of a bright area due to illumination.

  Next, two threshold processes will be described. In the fixed threshold processing, which is the first threshold processing, binarization is performed on all pixels of the preprocessed image with a fixed threshold from the discriminant analysis method. As a feature of this processing, all numbers can be extracted when the influence of illumination is relatively small, but the threshold value is fixed when the influence of illumination is strong. For example, FIG. 13B or FIG. As shown in the example of cutting out numbers), a part of the numbers is lost due to illumination. For example, in the example shown in FIG. 13B, the 1's digit of the numbers “400” and “600” is partially missing. For example, in the example shown in FIG. 14A, a part of the number on the right side of the number “1” is missing.

  In dynamic threshold processing, which is the second threshold processing, a moving average method for determining a threshold for each pixel is used. This is to use an average value of luminance values of neighboring pixels (61 × 61) when determining a threshold value of a certain pixel. A threshold value is determined for each pixel and binarized. Since the threshold value is dynamically determined as a feature of this processing, there is an advantage that numbers can be cut out well even in an area where the influence of illumination is strong. On the other hand, since threshold processing is performed even in an area where no number exists, for example, FIG. As shown in FIG. 14B, a region where no number exists is partially cut out. For example, in the area 104 in FIG. 14B, noise is introduced by using the average value of the luminance values of the neighboring pixels as a threshold value for the pixels in the area, so that there is essentially no number. It is an area that will be cut out.

  A number is cut out by combining the results of these two threshold processes. According to the dynamic threshold processing, for example, even when a part of a number is illuminated and the luminance value of the pixel of the number part that is illuminated is high, the threshold for pixels in the area Since the average value of the luminance values of the pixels in the vicinity of the pixel is used, the luminance value of the pixel portion of the numbered portion that is illuminated is lower than the average value (threshold value) of the luminance values of the pixels in the vicinity. Are extracted as number candidate areas. Therefore, generally, the number candidate region obtained is larger in the region cut out by the dynamic threshold processing. For example, the number candidate area shown in FIG. 14B is larger than the number candidate area shown in FIG.

  Therefore, the number recognizing unit 125 selects, as a number cut-out area, an area that overlaps the number candidate area obtained by the fixed threshold value processing among the number candidate areas obtained by the dynamic threshold value process.

  FIG. 13D or FIG. 14C shows an example of a number cut-out result when a number is cut out by surrounding a number rectangle after combining dynamic threshold processing and fixed threshold processing. By combining the results of the two threshold processes as described above, it is possible to cut out numbers that are robust against the influence of illumination.

(B) Recognition of numbers hidden by the pointers The numbers on the display panel of the round instrument 2 are difficult to cut out and recognize when they overlap the pointers. Since the position of the pointer changes depending on the current state of the system, it is conceivable that the position of the pointer is different from the previously captured image. In the embodiment of the present invention, for example, the instrument structure learning unit 12 may be configured to include a module that generates an image from which the pointer is removed by combining a plurality of original images having different pointer positions. By extracting the number area using the generated image from which the hands are removed, it is possible to recognize the numbers hidden behind the hands.

  The pointer has a relatively low luminance value compared to the display panel background. For example, between two original images taken at different times, the luminance value of each corresponding pixel is compared, and the luminance value of the pixel with the lower luminance value is changed to the luminance value of the pixel with the higher luminance value. By replacing, an image from which the pointer is removed is generated.

  For example, using the original image shown in FIG. 15 (A) and the original image shown in FIG. 15 (B), the luminance value of the pixel with the lower luminance value between the corresponding pixels is changed to the luminance value with the higher luminance value. In place of the luminance value of the pixel, for example, an image from which the pointer is removed is generated as shown in FIG.

(Explanation of distortion correction by shooting angle)
Generally, when an instrument is photographed at an angle with respect to the front, the instrument on the image is distorted. In general, a distortion leads to a decrease in accuracy in the number recognition processing and the number position determination processing. Therefore, in another embodiment of the present invention, for example, the instrument structure learning unit 12 corrects distortion by enlarging the image of the display board area extracted by the display board area extracting unit 121 at a vertical and horizontal unequal magnification. It is also possible to take a configuration with modules for performing. Here, an image whose distortion has been corrected is referred to as a frontalized image.

  When the round instrument 2 is photographed from the front, the shape of the image in the display panel area is a circle. On the other hand, when the image is taken from an oblique direction, the original image is distorted as shown in FIG. 16B, for example, and the shape of the image in the display panel area is an ellipse having different vertical and horizontal lengths. When the image is taken from the upper side or the lower side, distortion in the oblique direction occurs. Here, the distortion in the vertical direction or the horizontal direction is corrected. With respect to the outline of the display board area of the round instrument 2 extracted by the display board area extracting means 121, the maximum length in the vertical direction is examined as shown in FIG. Examine the maximum length in the horizontal direction as shown. With these as the diameters in the vertical and horizontal directions, the enlargement ratio is determined so that the short diameter is aligned with the long diameter, and the image is enlarged only in one direction. As a result, an image whose distortion is corrected is generated as shown in FIG. By performing the region division process and the number recognition process using the generated distortion-corrected image, it is possible to prevent a decrease in accuracy when determining the position of the number.

  The present invention can also be implemented as a program that is read and executed by a computer. The program for realizing the present invention can be stored in an appropriate recording medium such as a portable medium memory, a semiconductor memory, or a hard disk, which can be read by a computer, provided by being recorded on these recording media, or communication. It is provided by transmission / reception using a network via an interface.

It is a figure which shows an example of a structure of this invention. It is a figure which shows an example of the instruction value calculation processing flow of this invention. It is a figure explaining extraction of a display board area. It is a figure explaining extraction of a display board area. It is a figure which shows the example of the histogram of the intensity | strength of the black pixel for every angle. It is a figure which shows the example of a scale area | region, a number area | region, and a center and a pointer area | region. It is a figure which shows an example of the position determination process flow of a number. It is a figure which shows a number rectangle or the number recognized. It is a figure explaining the determination processing of the position of a number. It is a figure which shows the example of the positional information on the number accumulate | stored in a number position determination / accumulation | storage means. It is a figure explaining the correction process of the position shift of a number. It is a figure which shows the example of the positional information on a number. It is a figure which shows the example of cutting out a number. It is a figure which shows the example of cutting out a number. It is a figure which shows the image which removed the original image or the pointer | guide. It is a figure which shows an example of the image which correct | amended the original image and distortion. It is a figure explaining correction | amendment of the distortion of an image. It is a figure which shows the flow of a process of the general analog meter automatic reading system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image processing apparatus 2 Round instrument 3 Camera 11 Image input part 12 Instrument structure learning part 13 Instruction value calculation part 100 Contour line 101 of a display board area Virtual outline 102 Arrow 103 Scale 104 Area 121 Display board area extraction means 122 Area dividing means 123 Reference line determining means 124 Pointer position determining means 125 Number recognition means 126 Number position determining / accumulating means 127 Number position correcting means

Claims (8)

An image processing apparatus for processing an image of a round instrument photographed by an image photographing means and calculating an instruction value indicated by a pointer of the round instrument,
Image input means for inputting an image of the round instrument,
A display board area extracting means for extracting a display board area of the round instrument from the inputted round instrument image;
A reference line determining means for determining a straight line drawn vertically downward from the center of the display panel area as a reference line;
A pointer position determining means for extracting a center line of the pointer of the round instrument from the extracted display panel area, and determining an angle formed by the center line of the extracted pointer and the reference line as the position of the pointer; ,
The extracted display panel area is a scale area where a scale exists, a number area where a number indicating a numerical value of the scale is written, and a center of the display board area and a pointer. An area dividing means for dividing the center / pointer area,
Number recognition means for cutting out and recognizing numbers from the number area;
The angle formed by the straight line drawn from the center of the display panel area with respect to the center of gravity of each recognized number and the reference line is determined as the position of each number, and is stored in association with each number. Number position determination / accumulation means,
An image processing apparatus comprising: instruction value calculation means for calculating an instruction value indicated by the pointer based on the determined position information of the pointer and the accumulated position information of each numeral. The image processing apparatus according to claim 1, further comprising:
In the numeric string obtained by rearranging the position information of each numeral accumulated in the numeral position determining / accumulating means in ascending or descending order for the angle corresponding to each numeral, An image processing apparatus comprising: a numerical position correcting unit that detects an error in a numerical position and corrects positional information of each numeral. The image processing apparatus according to claim 2,
The numerical position correction means further includes:
The recognized numbers are associated with the scales included in the scale area, and the angles corresponding to the numbers stored in the number position determining / accumulating means are set to the numbers from the center of the display panel area. An image processing apparatus, wherein an angle formed by a straight line drawn with respect to the associated scale and the reference line is changed. The image processing device according to claim 1, further comprising:
An image processing apparatus comprising: a distortion correction unit that corrects distortion of an image in a display panel region of the round instrument extracted by the display panel region extraction unit. An image processing method for processing an image of a round instrument photographed by an image photographing means and calculating an instruction value indicated by a pointer of the round instrument,
An image input step for inputting an image of the round instrument;
A display board area extracting step for extracting a display board area of the round instrument from the inputted round instrument image;
A reference line determination step for determining a straight line drawn vertically downward from the center of the display panel area as a reference line;
A pointer position determining step for extracting a center line of the pointer of the round instrument from the extracted display panel area, and determining an angle formed by the center line of the extracted pointer and the reference line as the position of the pointer; ,
The extracted display panel area includes a scale area where a scale exists, a number area where a number indicating a scale value is written, a center of the display board area and a pointer. An area dividing step to divide into a center / pointer area,
A number recognition step of cutting out and recognizing numbers from the number region;
An angle formed by a straight line drawn from the center of the display panel area with respect to the center of gravity of each recognized number and the reference line is determined as a position of each number, and is stored in association with each number. Number position determination / accumulation step to be accumulated inside,
An instruction value calculating step of calculating an instruction value indicated by the pointer based on the determined position information of the pointer and the accumulated position information of each numeral. 6. The image processing method according to claim 5, further comprising:
In the numeral string obtained by rearranging the position information of each numeral stored in the storage means in the numeral position determination / accumulation step in ascending or descending order with respect to the angle corresponding to each numeral, An image processing method comprising: a numerical position correcting step of detecting an error in the position of each numeral from the magnitude relationship and correcting the positional information of each numeral. The image processing method according to claim 6,
The numerical position correction step further includes:
The recognized numbers are associated with the scales included in the scale area, and the angles corresponding to the numbers stored in the storage means are associated with the numbers from the center of the display panel area. An image processing method comprising: changing to an angle formed by a straight line drawn with respect to the scale and the reference line. The image processing method according to any one of claims 5 to 7, further comprising:
An image processing method comprising: a distortion correction step of correcting distortion of an image of a display panel area of the round instrument extracted by the display panel area extraction step.

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