Patent Publication Number: US-2019191075-A1

Title: Image processing apparatus and computer-readable storage medium

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a division of U.S. patent application Ser. No. 15/257,945, filed on Sep. 7, 2016, which application is a division of U.S. patent application Ser. No. 14/680,845, filed on Apr. 7, 2015, now U.S. Pat. No. 9,466,001, issued on Oct. 11, 2016, the entire contents of each of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to an image processing apparatus and a computer-readable storage medium. 
     BACKGROUND 
     In general, a manager of a warehouse or a shop manages a number of articles on shelves. These articles are managed by an apparatus which photographs the articles and identifies the character strings described on the labels attached to the articles shown in the image. The portion of the character string in the image is a binary image region. The binary image region in the image should be clear enough for the apparatus to identify the character string. Therefore, a technique for allowing the clarity of the binary image region to be determined quantitatively is required. 
     The embodiments described herein solve the above problem by providing an image processing apparatus and a computer-readable storage medium which are capable of quantitatively determining the clarity of the binary image region. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an image processing apparatus. 
         FIG. 2  shows diagrams explaining traveling directions of the image processing apparatus. 
         FIG. 3A ,  FIG. 3B , and  FIG. 3C  show diagrams explaining indexes used for determining clarity. 
         FIG. 4A ,  FIG. 4B ,  FIG. 4C ,  FIG. 4D ,  FIG. 4E , and  FIG. 4F  show diagrams indicating values of SERs calculated by the image processing apparatus. 
         FIG. 5  is a flowchart of an example of processes performed by the image processing apparatus. 
         FIG. 6  is a flowchart of another example of processes performed by the image processing apparatus. 
         FIG. 7A ,  FIG. 7B ,  FIG. 7C , and  FIG. 7D  show images of comparative examples. 
         FIG. 8A ,  FIG. 8B ,  FIG. 8C ,  FIG. 8D ,  FIG. 8E , and  FIG. 8F  show diagrams explaining a method of determining clarity by an image processing apparatus. 
         FIG. 9  is a flowchart of an example of processes performed by the image processing apparatus. 
         FIG. 10  is a flowchart of another example of processes performed by the image processing apparatus. 
         FIG. 11  is a block diagram of an image processing apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, an image processing apparatus includes an operation unit, a comparative determination unit, and an output unit. The operation unit is configured to calculate a standard deviation and an entropy based on tone information of pixels comprising an image, and calculate a ratio between the standard deviation and the entropy. The comparative determination unit is configured to compare the ratio and a reference value. The output unit is configured to output a comparison result obtained by the comparative determination unit. 
     Hereinafter, embodiments will be explained with reference to the drawings. 
     First Embodiment 
     The first embodiment is explained below.  FIG. 1  is a block diagram of an image processing apparatus  10  according to the first embodiment. 
     The image processing apparatus  10  is used for inventory control etc. of a plurality of articles placed on a shelf  20  of a warehouse or a store. The image processing apparatus comprises a moving vehicle  11 , a controller  12 , a photographing unit  13 , a processor  14 , a storage unit  15 , a display unit  16 , and an audio output unit  17 . The image processing apparatus  10  does not necessarily have to comprise all of these elements. For example, the image processing apparatus  10  may at least comprise the processor  14  and the storage unit  15 . 
     The moving vehicle  11  is a platform truck capable of moving the image processing apparatus  10  in any direction. The moving vehicle  11  is capable of traveling in a direction parallel to an extending direction of a linearly disposed shelf  20 , or a direction perpendicular thereto. 
     The controller  12  controls the operation of the moving vehicle  11  based on a signal from the processor  14 . The controller  12  controls the traveling direction of the moving vehicle  11 , or a start and stop of the traveling. The operation of the moving vehicle  11  may be determined either at the processor  14  or the controller  12 . 
     The photographing unit  13  is a camera which comprises a lens  131  and photographs a target. The photographing unit  13  may be a camera for photographing a moving image or a still image. The photographing unit  13  sends data of a photographed image to the processor  14 . 
     The processor  14  corresponds to the center portion of the image processing apparatus  10 . The processor  14  controls each element of the image processing apparatus  10  in accordance with an operating system or an application program. The processor  14  comprises an operation unit  141  and a comparative determination unit  142 . The processor  14  quantitatively determines, by the operation unit  141  and the comparative determination unit  142 , the clarity of a binary image region included in one image photographed by the photographing unit  13 . The binary image region is, for example, a region of an image in which letters and symbols etc. are projected. The clarity of the binary image region corresponds to the readability of the binary region, or the extent to which the binary image region is out of focus. The method of quantitatively determining the clarity of the binary image region included in this one image (hereinafter, referred to as clarity determination) will be explained later on. 
     The processor  14  sends an instruction for operating the moving vehicle  11  to the controller  12 . The processor  14  may also send the result of the clarity determination itself to the controller  12 . In this case, the controller  12  determines the operation of the moving vehicle  11  based on the clarity determination. 
     The processor  14  sends a signal regarding display at the display unit  16  to the display unit  16 . The processor  14  sends a signal regarding audio output at the audio output unit  17  to the audio output unit  17 . 
     The storage unit  15  includes a memory which stores the operating system and the application program. The storage unit  15  further includes a memory that serves as a work area necessary for the processing performed by the processor  14 . The storage unit  15  further includes a memory that stores data necessary for the processing performed by the processor  14 . The storage unit  15  stores a plurality of reference values  151 . The plurality of reference values  151  are threshold values for clarity determination. 
     The display unit  16  is a display for displaying videos based on the signal from the processor  14 . The audio output unit  17  is a speaker which outputs audio based on the signal from the processor  14 . The display unit  16  and the audio output unit  17  are output units. 
       FIG. 2  shows diagrams explaining a traveling direction of an image processing apparatus  10  according to the first embodiment. The left diagram in  FIG. 2  and the right diagram in  FIG. 2  are viewed from right angles to each other. Referring to the left diagram in  FIG. 2 , the moving vehicle  11  travels causing the image processing apparatus  10  to move in parallel with the extending direction of the shelf  20 . Therefore, the photographing unit  13  is capable of photographing each label attached to a plurality of articles mounted on the shelf  20  in sequence while moving in parallel with the extending direction of the self  20 . 
     Referring to the right diagram in  FIG. 2 , the moving vehicle  11  travels causing the image processing apparatus  10  to stop moving in parallel with the extending direction of the shelf  20  and to move in a direction perpendicular to the extending direction of the shelf  20 . The image processing apparatus  10  moves to a direction perpendicular to the extending direction of the shelf  20  in order to maintain appropriate distance between the photographing unit  13  and a photographing target (the shelf  20 , more specifically, an article mounted on the shelf  20 ). The distance between the photographing unit  13  and the photographing target may be rephrased as the distance between the moving vehicle  11  and the shelf  20 . Therefore, the image processing apparatus  10  is capable of maintaining the clarity of the binary image region included in each image photographed in sequence by the photographing unit  13 . 
     The indexes used for clarity determination are explained below.  FIGS. 3A-3C  show diagrams explaining the indexes used for determining clarity according to the first embodiment.  FIGS. 3A-3C  show data regarding three different binary images. The entire image of each of the three images is a binary image region. In  FIGS. 3A-3C , data indicated as “ 1 ” corresponds to a first image which is in focus. The first image is a clear image. In  FIGS. 3A-3C , data indicated as “ 2 ” corresponds to a second image which is less in focus than the first image. The second image is not as clear as the first image. In  FIGS. 3A-3C , data indicated as “ 3 ” corresponds to a third image which is more out of focus than the second image. The third image is not as clear as the second image. 
       FIG. 3A  is a graph showing data of any one line of each of the first image, the second image, and the third image as an input function. The horizontal axis indicates the coordinate of each pixel included in the any one line of one image, and the vertical axis indicates a tone (pixel value). The processor  14  generates the input function from data of one image which is the target of clarity determination. The any one line may correspond to the horizontal axis or the vertical axis of the entire one image. 
       FIG. 3B  is a graph showing a histogram of each of the first image, the second image, and the third image. The horizontal axis indicates a tone, and the vertical axis indicates the number of pixels. The histogram shows the distribution of pixels included in any one line of one image subject to clarity determination, and is tone information of the pixels comprising the image. The processor  14  generates the histogram from the input function. The two peaks in the histogram become sharper as the binary image becomes clearer. Furthermore, the positions of the two peaks in the histogram become more distant as the binary image becomes clearer. 
       FIG. 3C  is a graph showing the ratio between a standard deviation σ and an entropy S (σ/S) (hereinafter, referred to as SER) in each of the first image, the second image, and the third image. The processor  14  calculates the standard deviation σ and the entropy S based on the histogram using the following formula. Subsequently, the processor  14  calculates the SER based on the standard deviation σ and the entropy S. 
     The formula of the standard deviation σ is as follows. 
     
       
         
           
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     The formula of the entropy S is as follows. 
     
       
         
           
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     Here, n i  is the number of pixels of tone i in the histogram, and n is the total number of pixels in the histogram. 
     The standard deviation σ is an index expressing separation of at least two peaks in the histogram. The entropy S is an index expressing sharpness in the peaks in the histogram. The SER is an index expressing the clarity of the binary image region quantitatively. The standard deviation σ becomes larger as the two peaks become more distant in the histogram. The entropy S becomes smaller as the two peaks become sharper in the histogram. If the standard deviation σ is large and the entropy S is small, the value of the SER is large. 
     Referring to  FIG. 3C , the SER becomes larger in the order of the third image, the second image, and the first image. This is the order in which the images become more in focus. If the SER is large, the binary image region is considered clear. Therefore, the SER is effective as an index for quantitatively expressing the clarity of the binary image region. 
     The SER should be a ratio of an index (standard deviation σ is an example) expressing separation of at least two peaks in the histogram, and an index (entropy S is an example) expressing sharpness of the peaks in the histogram. Therefore, the processor  14  may calculate the SER using indexes other than the standard deviation σ and the entropy S. For example, the magnitude of the standard deviation σ changes depending on the brightness of the entire image. Therefore, it is favorable for the processor  14  to calculate the SER using a coefficient of variation obtained by dividing the standard deviation σ by an average value m, instead of using the standard deviation σ. The processor  14  may also calculate the SER using a variance which is a square of the standard deviation σ, instead of using the standard deviation σ. When calculating the entropy S, the processor  14  divides the number of pixels ni of each tone by the number of the entire pixels n. However, the number of pixels ni of each tone does not have to be divided by the number of the entire pixels n. 
     The SER is not limited to a value that is calculated based on any line of one image. For example, the SER may be an average value of a plurality of SERs calculated from any plurality of lines or all of the lines of one image. 
     SER differences in different images will be explained below.  FIGS. 4A-4F  show diagrams indicating values of SERs calculated by the processor  14  according to the first embodiment.  FIGS. 4A-4F  show three different images in which the same character string ABCD is projected, with respective histograms and respective SERs. 
       FIG. 4A  is a fourth image which is in focus. The fourth image is a clear binary image. The entire image of the fourth image is a binary image region.  FIG. 4C  is a fifth image which is more out of focus than the fourth image. The fifth image is a binary image which is more unclear than the fourth image. The entire image of the fifth image is a binary image region.  FIG. 4E  is a sixth image which is more out of focus than the fourth image, however, is more in focus than the fifth image. The sixth image is more unclear than the fourth image, however, is clearer than the fifth image. However, the sixth image overall has a lower contrast than the fourth image. 
     The processor  14  may calculate the standard deviation σ, the entropy S, and the SER of each of the fourth image, the fifth image, and the sixth image in the manner mentioned above using  FIGS. 3A-3C . 
     As shown in  FIG. 4B , in the fourth image, the standard deviation σ is 82, the entropy S is 0.6, and the SER is 68. As shown in  FIG. 4D , in the fifth image, the standard deviation σ is 71, the entropy S is 1.1, and the SER is 31. As shown in  FIG. 4F , in the sixth image, the standard deviation σ is 31, the entropy S is 0.5, and the SER is 29. 
     The SER in the fourth image is equal to or more than twice that of the fifth image. This reflects the difference of the entropy S between the two images. However, the SER in the sixth image is approximately half that of the fourth image. This reflects the difference of the standard deviation σ between the two images. 
     The processor  14  is capable of determining whether or not the binary image region included in the image is clear by comparing the SER and the reference value. If the SER is larger than the reference value, the processor  14  determines that the binary image region is clear. However, if the SER is not larger than the reference value, the processor  14  determines that the binary image region is unclear, or that the contrast of the image itself is low. Therefore, the SER is not only an index which can be used to evaluate the state of clarity of the binary image region, but is also an index which can be used to evaluate the state of contrast of the image itself simultaneously. Thus, the SER is effective as an index for expressing the clarity of the binary image region quantitatively. 
     An example of processes performed by the image processing apparatus  10  is explained below.  FIG. 5  is a flowchart of an example of processes performed by the image processing apparatus  10  according to the first embodiment. 
     The moving vehicle  11  starts traveling based on the control performed by the controller  12  (Act 1001 ). The moving vehicle  11  travels along a direction in parallel with the extending direction of the shelf  20 . The photographing unit  13  photographs articles (photographing target) placed on the shelf  20  while moving (Act 1002 ). The processor  14  retrieves the image photographed by the photographing unit  13  (Act 1003 ). The image retrieved by the processor  14  from the photographing unit  13  in Act 1003  is the target image for clarity determination. The processor  14  calculates the standard deviation σ and the entropy S based on the entropy of the target image for clarity determination, and calculates the SER based on the standard deviation σ and the entropy S (Act 1004 ). Act 1004  is performed, for example, by the operation unit  141  in the processor  14 . 
     The processor  14  compares the SER with a first threshold value (Act 1005 ). Act 1005  is performed, for example, by the comparative determination unit  142  in the processor  14 . The first threshold value corresponds to a first reference value stored in the storage unit  15 . The first reference value is a reference for determining whether or not the binary image region included in the image is clear. The first reference value may be set to any value in advance. For example, the first reference value may correspond to the SER of an image including a clear binary image region photographed in advance. If the SER is not larger than the first threshold value, the binary image region is not clear, or the binary image region is not included in the image itself. However, if the SER is larger than the first threshold value, the binary image region is clear. 
     If the SER is not larger than the first threshold value (Act 1005 , No), the controller  12  controls the moving vehicle  11  to stop traveling based on the signal from the processor  14  (Act 1006 ). The controller  12  controls the moving vehicle to stop traveling based on a stop command from the processor  14 . The controller  12  may also decide on stopping the moving vehicle  11  based on the result of a comparison between the SER sent from the processor  14  and the first threshold value. 
     If the processor  14  determines that the SER is not larger than the first threshold value in Act 1005 , the processor  14  may send the comparison result between the SER and the first threshold value to at least one of the display unit  16  and the audio output unit  17 . The display unit  16  and the audio output unit  17  output the comparison result sent by the processor  14 . The display unit  16  displays the comparison result sent by the processor  14 . The audio output unit  17  outputs the comparison result sent by the processor  14  by audio. For example, the comparison result may be the SER and the first threshold value. As another example, the comparison result may be a warning that the binary image region is unclear, or that the photographing unit  13  is out of focus etc. The output from the display unit  16  or the audio output unit  17  will allow a manager to recognize the state of the binary image region included in the image photographed by the photographing unit  13 . 
     Based on the comparison result, the controller  12  controls the distance between the photographing unit  13  and the photographing target projected in the current image to be corrected (Act 1007 ). In Act 1007 , the controller  12  controls the position of the moving vehicle  11  so that the photographing unit  15  is brought into focus. For example, the controller  12  controls the moving vehicle  11  to travel at a predetermined distance from the shelf  20  in a direction which shortens or increases the distance of the moving vehicle  11  to the shelf  20 . The photographing target is the shelf  20 , more specifically, the article placed on the shelf  20 . The traveling distance of the moving vehicle can be set as desired. The process returns to Act 1002 , in which the photographing unit  13  photographs the same photographing target again. In other words, the image processing apparatus processes a plurality of images in which the same photographing target is photographed in Act 1002  to Act 1007  until the SER of the image in which the same photographing target is projected becomes larger than the first threshold value. 
     If the SER is larger than the first threshold value (Act 1005 , Yes), the processor  14  stores the current image subject to clarity determination in the storage unit  15  (Act 1008 ). The process returns to Act 1001 , in which the moving vehicle  11  starts to travel. The image processing apparatus  10  performs clarity determination of a binary image region included in an image which shows the next photographing target. 
     According to the processes shown in  FIG. 5 , the image processing apparatus  10  is capable of quantitatively determining the clarity of a binary image region included in an image by using the SER. Therefore, the image processing apparatus  10  is capable of storing each clear image of different photographing targets sequentially while maintaining the distance between the moving vehicle  11  and the shelf  20  appropriately. 
     Another example of the processes performed by the image processing apparatus  10  is explained below.  FIG. 6  is a flowchart of another example of processes performed by the image processing apparatus  10  according to the first embodiment. 
     The explanations of Act 2001  to Act 2004  and Act 2006  to Act 2008  of  FIG. 6  will be omitted since they are respectively the same as Act 1001  to Act 1004  and Act 1006  to Act 1008 . 
     In Act  2005 , the processor  14  determines whether or not the SER of the current image subject to clarity determination is at maximum. For example, Act 2005  is performed by the comparative determination unit  142  in the processor  14 . Here, the process carried out by the processor in Act 2005  will be explained assuming that the image subject to clarity determination shows a photographing target X. 
     In Act 2005 , the processor  14  determines whether or not the SER of a first piece of an image showing the photographing target X is at maximum. However, at this point, a second threshold value to which the SER of the first piece of an image is to be compared is not stored in the storage unit  15 . Therefore, the processor  14  stores the SER of the first piece of an image as a second reference value in the storage unit  15 . In other words, the second reference value corresponds to the SER of the past image in which the same photographing target X as the current image is shown. The second threshold value corresponds to the second reference value stored in the storage unit  15 . 
     Returning to Act  2005  after going through the processes of Act 2006 , Act 2007 , and Act 2002  to Act 2004 , the processor  14  determines whether or not the SER of a second piece of an image showing the photographing target X is at maximum. The second piece of an image is a current image subject to clarity determination. The processor  14  compares the SER of the second piece of an image with the second threshold value. If the SER of the second piece of an image is not larger than the second threshold value, the processor  14  determines that the SER corresponding to the second threshold value is at maximum. In other words, the processor  14  determines that an image showing a photographing target X with a maximum SER is found. In Act 2008 , the processor  14  stores the image which the calculation of the SER corresponding to the second threshold value is based on in the storage unit  15 . In other words, the binary image region of this image is regarded as clear. 
     If the SER of the second piece of an image is larger than the second threshold value, the processor  14  determines that the SER corresponding to the second threshold value is not at maximum. In other words, the processor  14  determines that an image showing a photographing target X with a maximum SER is not found yet. The processor  14  updates the second reference value based on the SER of the second piece of an image and stores it in the storage unit  15 . 
     Returning again to Act  2005  after going through the processes of Act 2006 , Act 2007 , and Act 2002  to Act 2004 , the processor  14  determines whether or not the SER of a third piece of an image showing the photographing target X is at maximum. In other words, the image processing apparatus  10  continues processing different images in which the same photographing target X is shown until an SER which is not larger than the second threshold value is found in Act 2005 . In the manner mentioned above, in Act 2005 , the processor  14  determines an image which becomes the basis of calculating the maximum SER among a plurality of images in which the same photographing target is shown. 
     If the processor  14  determines that the SER of the current image subject to clarity determination is not at maximum in Act 1005 , as explained in  FIG. 6 , the display unit  16  and the audio output unit  17  may output the comparison result obtained by the processor  14 . For example, the comparison result is the SER and the second threshold value. As another example, the comparison result is a warning that the clarity of the binary image region is not at maximum, or that the photographing unit  13  is out of focus, etc. 
     According to the processes shown in  FIG. 6 , the image processing apparatus  10  is capable of obtaining an image in which a binary image region has higher clarity than an image obtained by the processes shown in  FIG. 5 . 
     Second Embodiment 
     The second embodiment is explained below. Here, those sections which are different from the first embodiment will be explained; the explanation of those sections which are the same as the first embodiment is omitted. 
       FIGS. 7A-7D  show images of comparative examples.  FIG. 7  shows two different images in which the same character string ABCD is projected, with respective histograms and respective SERs.  FIG. 7A  is a seventh image which is in focus. The seventh image is a clear image.  FIG. 7C  is an eighth image which is more out of focus than the seventh image. In the seventh image and the eighth image, a natural image region surrounds a binary image region. As shown in  FIG. 7B , the SER of the seventh image is 12. As shown in  FIG. 7D , the SER of the eighth image is 8. There is no sufficient difference between the SER of the seventh image which is in focus and the SER of the eighth image which is out of focus. Therefore, it may be difficult for the image processing apparatus  10  to determine the clarity of the binary image region included in the image only by calculating one SER from one image which is subject to clarity determination. Therefore, the image processing apparatus  10  according to the second embodiment divides one image subject to clarity determination into a plurality of blocks in the manner explained below and calculates the SER of each block. 
       FIGS. 8A-8F  show diagrams explaining a method of determining clarity by a processor  14  according to the second embodiment.  FIGS. 8A and 8D  are two different images projecting the same character string ABCD as in  FIGS. 7A and 7C . 
       FIG. 8A  is a ninth image which is in focus. The ninth image is a clear image.  FIG. 8D  is a tenth image which is more out of focus than the ninth image. The tenth image is not as clear as the ninth image. In the ninth image and the tenth image, a natural image region surrounds a binary image region. 
     In the second embodiment, the processor  14  divides one image subject to clarity determination into a plurality of blocks and calculates the SER of each block. Referring to  FIGS. 8A and 8D , the processor  14  divides the ninth image and the tenth image into 64 blocks. The processor  14  calculates the SER of each block in the manner explained in the first embodiment based on data of any one line per block. The any one line may correspond to a horizontal axis or a vertical axis of each block. The SER of each block may be an average value of a plurality of SERs calculated from any plurality of lines or all of the lines of each block. The image may be divided into any number of blocks. 
     In  FIG. 8B , a histogram is arranged at a position corresponding to each block of the ninth image. In  FIG. 8C , the value of an SER is indicated at a position corresponding to each block of the ninth image. In the ninth image, the value of the SER of the blocks corresponding to the binary image region is equal to or greater than 40. 
     In  FIG. 8E , a histogram is arranged at a position corresponding to each block of the tenth image. In the  FIG. 8F , the value of an SER is indicated at a position corresponding to each block of the tenth image. In the tenth image, the value of the SER of the blocks corresponding to the binary image region is equal to or less than 20. Unlike the example shown in  FIGS. 7A-7D , in the blocks corresponding to the binary image region, the difference between the SER of an image in focus and the SER of an image out of focus is significant. Therefore, even if it is difficult for the image processing apparatus  10  to determine the clarity of the binary image region based on one SER calculated from one image subject to clarity determination, the clarity of the binary image region can be determined based on each SER calculated from each block of this image. 
     The processor  14  determines whether or not the binary image region included in the image is clear by comparing the SER and the reference value of each block. If the SER of the block is larger than the reference value, the processor  14  determines that the binary image region included in the block is clear. However, if the SER of the block is not larger than the reference value, the processor  14  determines that the binary image region included in the block is unclear. The SER is effective as an index for quantitatively expressing the clarity of the binary image region even in an image where a natural image region and a binary image region coexist. 
     An example of the processes performed by the image processing apparatus  10  is explained below.  FIG. 9  is a flowchart of an example of processes performed by the image processing apparatus  10  according to the second embodiment. 
     The moving vehicle  11  starts traveling based on the control performed by the controller  12  (Act 3001 ). The moving vehicle  11  travels along a direction parallel to the extending direction of the shelf  20 . The photographing unit  13  photographs an object (photographing target) placed on the shelf  20  while moving (Act 3002 ). The processor  14  retrieves the image photographed by the photographing unit  13  (Act 3003 ). The image retrieved by the processor  14  from the photographing unit  13  in Act 3003  is the image subject to clarity determination. 
     The processor  14  divides this image into a plurality of blocks (Act 3004 ). The processor  14  calculates a standard deviation σ and an entropy S based on the entropy of each block in the plurality of blocks, and calculates the SER of each block based on the standard deviation σ and the entropy S (Act 3005 ). Act 3005  is performed, for example, by the operation unit  141  in the processor  14 . 
     The processor  14  acquires the number of OK blocks based on the value of each SER (Act 3006 ). The OK block corresponds to a block including a clear binary image region. In Act 3006 , for example, the processor  14  acquires the number of OK blocks in the manner below. The processor  14  compares the SER of each block with a third threshold value. The third threshold value corresponds to a third reference value stored in the storage unit  15 . The third reference value is a reference for determining whether or not a binary image region included in each block is clear. The third reference value may be set as desired in advance. For example, the third reference value may correspond to an SER value of an image including a clear binary image region photographed in advance. If the SER of the block is not larger than the third threshold value, it indicates that the binary image region included in this block is not clear, or that the binary image region is not included in the block itself. However, if the SER of the block is larger than the third threshold value, it indicates that the binary image region included in this block is clear. 
     If the SER of a given block is larger than the third threshold value, the processor  14  determines that this block is an OK block. However, if the SER of a given block is not larger than the third threshold value, the processor  14  determines that this block is not an OK block. The processor  14  compares the SER of every block that comprises the image that is subject to clarity determination with the third threshold value. The processor  14  acquires the number of OK blocks from the entire block that comprises the image subject to clarity determination. Here, a value obtained by dividing the number of OK blocks in the image subject to clarity determination by the total number of blocks comprising this image is referred to as a first ratio. 
     The processor  14  compares the first ratio with a fourth threshold value (Act 3007 ). A fourth reference value is a reference for determining whether or not a binary image region included in an image is clear. The fourth reference value may be set as desired in advance. For example, the fourth reference value may be a value obtained by dividing the number of OK blocks in an image including a clear binary image region photographed in advance by the total number of blocks comprising this image. 
     If the first ratio is not larger than the first threshold value, it indicates that the binary image region included in the image is not clear, or that the binary image region is not included in the image itself. However, if the first ratio is larger than the first threshold value, it indicates that the binary image region included in the image is clear. 
     If the first ratio is not larger than the fourth threshold value (Act 3007 , No), the controller  12  controls the moving vehicle  11  to stop traveling based on the signal from the processor  14  (Act 3008 ). In Act 3008 , the image processing apparatus  10  may carry out the same process as Act 1006  mentioned above. If the processor  14  determines that the first ratio is not larger than the fourth threshold value in Act 3007 , as explained in  FIG. 5 , the display unit  16  and the audio output unit  17  may output the comparison result. For example, the comparison result is the first ratio and the fourth threshold value. As another example, the comparison result may be a warning that the binary image region is unclear, or that the photographing unit  13  is out of focus etc. 
     The controller  12  then corrects the position of the moving vehicle  11  so that the photographing unit  15  comes in focus (Act 3009 ). In Act 3009 , the image processing apparatus  10  may carry out the same process as Act 1007  mentioned above. The process returns to Act 3002 , in which the photographing unit  13  photographs the same photographing target again. In other words, the image processing apparatus  10  processes a plurality of images in which the same photographing target is photographed by Act 3002  to Act 3009  until the first ratio of the image showing the same photographing target becomes larger than the fourth threshold value. 
     If the first ratio is larger than the fourth threshold value (Act 3007 , Yes), the processor  14  stores the present image which is subject to clarity determination in the storage unit  15  (Act 3010 ). The process returns to Act 3001 , in which the moving vehicle  11  starts traveling. The image processing apparatus  10  performs clarity determination of a binary image region included in an image which shows the next photographing target. 
     Another example of the processes performed by the image processing apparatus  10  is explained below.  FIG. 10  is a flowchart of another example of processes performed by the image processing apparatus  10  according to the second embodiment. 
     Since Act 4001  to Act 4006  and Act 2008  to Act 4010  of  FIG. 10  are the same as Act 3001  to Act 3006  and Act 3008  to Act 3010  of  FIG. 9 , the explanations thereof will be omitted. 
     In Act  4007 , the processor  14  determines whether or not the first ratio of the current image subject to clarity determination is at maximum. Act 4007  is performed by the comparative determination unit  142  in the processor  14 . Here, the process carried out by the processor  14  in Act 4007  will be explained assuming that the image subject to clarity determination shows a photographing target Y. 
     In Act 4007 , the processor  14  determines whether or not the first ratio of a first piece of an image showing the photographing target Y is at maximum. However, at this point, a fifth threshold value to which the first ratio of the first piece of an image is to be compared is not stored in the storage unit  15 . Therefore, the processor  14  stores the first ratio of the first piece of an image as a fifth reference value in the storage unit  15 . In other words, the fifth reference value corresponds to the first ratio of the past image in which the same photographing target Y as the current image is shown. The fifth threshold value corresponds to the fifth reference value stored in the storage unit  15 . 
     Returning to Act  4007  after going through the processes of Act 4008 , Act 4009 , and Act 4002  to Act 4006 , the processor  14  determines whether or not the first ratio of a second piece of an image showing the photographing target Y is at maximum. The second piece of an image is a current image which is subject to clarity determination. The processor  14  compares the first ratio of the second piece of an image with the fifth threshold value. If the first ratio of the second piece of an image is not larger than the fifth threshold value, the processor  14  determines that the first ratio which corresponds to the fifth threshold value is at maximum. In other words, the processor  14  determines that an image showing a photographing target Y with a maximum first ratio is found. In Act 4010 , the processor  14  stores the image which the calculation of the first ratio corresponding to the fifth threshold value is based on in the storage unit  15 . In other words, the binary image region of this image is regarded as clear. 
     If the first ratio of the second piece of an image is larger than the fifth threshold value, the processor  14  determines that the first ratio which corresponds to the fifth threshold value is not at maximum. In other words, the processor  14  determines that an image showing a photographing target with a maximum first ratio is not found yet. The processor  14  updates the fifth reference value based on the first ratio of the second piece of an image and stores it in the storage unit  15 . 
     In Act  4007 , which comes after Act 4008 , Act 4009 , and Act 4002  to Act 4006 , the processor  14  determines whether or not the first ratio of a third piece of an image showing the photographing target Y is at maximum. In other words, the image processing apparatus  10  continues processing different images in which the same photographing target Y is shown until a first ratio that is not larger than the fifth threshold value is found in Act 2007 . In the manner mentioned above, in Act 2007 , the processor  14  determines an image which is to be the basis of calculating the maximum first ratio among a plurality of images which show the same photographing target. 
     If the processor  14  determines that the first ratio of the current image subject to clarity determination is not at maximum in Act 2007 , as explained using  FIG. 5 , the display unit  16  and the audio output unit  17  may output the comparison result. For example, the comparison result is the first ratio and the fifth threshold value. As another example, the comparison result is a warning that the clarity of the binary image region is not at maximum, or that the photographing unit  13  is out of focus, etc. 
     The image processing apparatus  10  according to the second embodiment is capable of determining the clarity of a binary image region in an image in which a natural image region and a binary image region coexist more accurately than the image processing apparatus  10  according to the first embodiment. 
     Third Embodiment 
     The third embodiment is explained below.  FIG. 11  is a block diagram of an example of an image processing apparatus  10  according to the third embodiment. For the configurations similar to the first embodiment, the same reference symbols as used in the first embodiment will be used, and the explanations thereof will be omitted. 
     A photographing unit  13  according to the third embodiment is a camera with an autofocus function and a focus determination function. The photographing unit  13  corrects the focus based on a signal from a processor  14 . 
     The example of the processing performed by the image processing apparatus  10  according to the third embodiment will be explained using  FIGS. 5, 6, 9, and 10 . The image processing apparatus  10  according to the third embodiment performs processes different from the first and the second embodiments in Act 1007  of  FIG. 5 , Act  2007  of  FIG. 6 , Act 3009  of  FIG. 9 , and Act 4009  of  FIG. 10 . 
     In Act 1007  of  FIG. 5 , Act  2007  of  FIG. 6 , Act 3009  of  FIG. 9 , and Act 4009  of  FIG. 10 , the photographing unit  13  corrects the focus of the photographing unit  13  to be brought into focus. The correction amount of the focus may be set as desired. The photographing unit  13  may correct the focus based on a comparison result sent from the processor  14 , or based on information of the focus correction amount sent from the processor  14 . 
     After Act 1007  of  FIG. 5 , Act  2007  of  FIG. 6 , Act 3009  of  FIG. 9 , and Act 4009  of  FIG. 10 , the photographing unit  13  photographs the same target again in a state where the focus is corrected. 
     The third embodiment is capable of obtaining the same effect as the first and the second embodiments. 
     As used in this application, entities for executing the actions can refer to a computer-related entity, either hardware, a combination of hardware and software, software, or software in execution. For example, an entity for executing an action can be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and a computer. By way of illustration, both an application running on an apparatus and the apparatus can be an entity. One or more entities can reside within a process and/or thread of execution and a entity can be localized on one apparatus and/or distributed between two or more apparatuses. 
     The program for realizing the functions can be recorded in the apparatus, can be downloaded through a network to the apparatus and can be installed in the apparatus from a computer readable storage medium storing the program therein. A form of the computer readable storage medium can be any form as long as the computer readable storage medium can store programs and is readable by the apparatus such as a disk type ROM and a Solid-state computer storage media. The functions obtained by installation or download in advance in this way can be realized in cooperation with an OS (Operating System) or the like in the apparatus. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.