JP2015089048A - Image processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform appropriate correction processing on input image data.SOLUTION: An image processing device includes: an image reading unit 41 for reading out input image data from a first image storage unit, to generate a first conversion image data; a histogram generator unit 43 for generating a histogram on the basis of the first conversion image data; a validity determination unit 44 for determining whether the histogram is valid; a parameter derivation unit 45 for setting a parameter when the histogram is valid; an image correction unit 46 for correcting the first conversion image data on the basis of the parameter; and an image output unit 54 for reading out an output image data recorded in a second image storage unit to output to an output device. Because the parameter is set when the histogram is valid, the parameter can be calculated with high accuracy on the basis of the histogram.

Description

  The present invention relates to an image processing apparatus.

  2. Description of the Related Art Conventionally, in an image processing apparatus such as a copying machine or a multifunction machine, for example, a multifunction machine, an image of a document is read by a scanner unit, and the read data is sent to the image processing unit as input image data, and input by the image processing unit Output image data is generated based on the image data and sent to the printer unit, and printing is performed based on the output image data in the printer unit.

  In this case, the image processing unit removes the background removal process for removing the color component (background color) of the background area of the document from the input image data, and removes the show-through that appears on the front surface of the image on the back side of the document. Correction processing such as show-through removal processing is performed.

  For this purpose, a histogram of density information in the input image data is created, the mode value of the histogram is calculated as a feature amount (reference density), and corrections such as the background removal processing and show-through removal processing are performed based on the feature amount. A process is performed (for example, refer patent document 1).

JP 2010-93684 A

  However, in the conventional multi-function device, if all density information of the input image data is acquired and a histogram is to be created, a memory having a large storage capacity for recording the histogram is required, and the cost of the multi-function device is reduced. It will be high.

  Therefore, sampling is performed by limiting input image data or thinning out density information, and the number of density information acquired by sampling, that is, the number of sampling is reduced, but if the number of sampling is small Therefore, it is not possible to accurately calculate the feature amount based on the histogram. Therefore, it becomes impossible to perform an appropriate correction process on the input image data.

  It is an object of the present invention to provide an image processing apparatus that can solve the problems of the conventional multi-function peripheral and can perform appropriate correction processing on input image data.

  Therefore, in the image processing apparatus of the present invention, the first image storage unit for recording the input image data acquired by the image input unit, and the input image data is read from the first image storage unit, An image reading unit that converts color space to generate first converted image data, a histogram generation unit that generates a histogram based on the first converted image data, and a histogram generated by the histogram generation unit are effective Based on the parameter set by the parameter deriving unit, the parameter deriving unit for setting a parameter for correcting the input image data when the histogram is valid, An image correction unit that corrects the first converted image data and generates second converted image data; and the second converted image data. Output image data by converting the color space, generating output image data, and reading and outputting the output image data recorded in the second image storage unit And an image output unit to be sent to the device.

  According to the present invention, in the image processing device, the first image storage unit for recording the input image data acquired by the image input unit, and the input image data is read from the first image storage unit, An image reading unit that converts color space to generate first converted image data, a histogram generation unit that generates a histogram based on the first converted image data, and a histogram generated by the histogram generation unit are effective Based on the parameter set by the parameter deriving unit, the parameter deriving unit for setting a parameter for correcting the input image data when the histogram is valid, An image correction unit that corrects the first converted image data and generates second converted image data; and the second converted image data Read, convert color space to generate output image data, and record in the second image storage unit; read out output image data recorded in the second image storage unit and output to the output device And an image output unit to be sent.

  In this case, it is determined whether or not the histogram created by the histogram creation unit is valid. If the histogram is valid, a parameter is set by the parameter deriving unit, and the first converted image data is generated based on the parameter. Since the correction is made, the parameters can be calculated with high accuracy based on the histogram. Therefore, an appropriate correction process can be performed on the input image data.

It is a control block diagram of the control part in the 1st Embodiment of this invention. 1 is a perspective view of a multifunction machine according to a first embodiment of the present invention. FIG. 2 is a control block diagram of the multifunction machine according to the first embodiment of the present invention. It is a control block diagram of the sampling condition determination part in the 1st Embodiment of this invention. It is a control block diagram of a parameter deriving unit in the first embodiment of the present invention. 3 is a first flowchart illustrating an operation of the multifunction peripheral according to the first embodiment of the present invention. It is a 2nd flowchart which shows operation | movement of the multifunctional device in the 1st Embodiment of this invention. It is a figure for demonstrating the thinning-out object pixel in the 1st Embodiment of this invention. It is a figure which shows the example of the frequency distribution of the histogram in the 1st Embodiment of this invention. It is a figure which shows the example of the setting conversion table in the 1st Embodiment of this invention. It is a figure which shows the example of the general purpose conversion table in the 1st Embodiment of this invention. It is a figure which shows the example of input image data in case the total number of pixels of a histogram is small. It is a figure which shows the example of output image data in case the total number of pixels of a histogram is small. It is a figure which shows the example of the histogram produced when the total number of pixels of a histogram is small. It is a control block diagram of the control part in the 2nd Embodiment of this invention. 6 is a first flowchart illustrating an operation of the multifunction peripheral according to the second embodiment of the present invention. It is a 2nd flowchart which shows operation | movement of the multifunctional device in the 2nd Embodiment of this invention. It is a figure which shows operation | movement of the image reading part in the 1st Embodiment of this invention, and an image writing part. It is a figure which shows operation | movement of the image reading part in the 2nd Embodiment of this invention, and an image writing part.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, a color multifunction peripheral as an image processing apparatus will be described.

  FIG. 2 is a perspective view of the multifunction device according to the first embodiment of the present invention, and FIG. 3 is a control block diagram of the multifunction device according to the first embodiment of the present invention.

  In the figure, 10 is a color multifunction peripheral, 20 is a scanner unit that reads an image of a document as a first medium and generates read data, and 30 receives the read data sent from the scanner unit 20 as image data. An electrophotographic printer unit, PL, is an operation panel as an output device for forming (printing) an image on a sheet as a second medium based on the image data. The operation panel PL is provided with an operation unit P1 including switches and buttons, and a display unit P2 including a liquid crystal panel.

  The scanner unit 20 includes a flat bed 101 as a mounting table on which a document is placed, a cover 102 that covers the flat bed 101, and an automatic document that is disposed on the cover 102 and automatically feeds the document. A feeding device (ADF) 103, a reading head (not shown) as an image reading unit that is arranged below the flat bed 101 and reads an image of a document, and based on the bitmap data based on an image signal generated by the reading head Image signal, that is, a signal processing unit (not shown) for generating input image data.

  The reading head includes a light source, a light receiving element, and the like. When reading an image of a document placed on the flat bed 101, the reading head is moved along the flat bed 101 and the document fed by the automatic document feeder 103 is read. When reading an image, it is placed at a predetermined position, irradiates light from a light source onto the document, and light reflected by the document, that is, reflected light is received by a light receiving element to generate an image signal. Send to processing section.

  The signal processing unit receives the image signal sent from the reading head, performs signal processing such as A / D conversion and shading correction on the image signal, generates the input image data, and inputs the image data via the input interface 11. This is sent to the control unit 12.

  The printer unit 30 includes a paper cassette 111 as a medium storage unit for storing paper, an image forming unit (not shown) of four colors of black, yellow, magenta, and cyan, and an image carrier disposed in each image forming unit. A photosensitive drum as an exposure apparatus, an LED head (not shown) as an exposure device disposed to face the respective photosensitive drums, a developing device disposed in each image forming unit, and the respective photosensitive drums to face each other. A transfer roller (not shown) serving as a transfer member disposed, a fixing device (not shown) serving as a fixing device, and the like are provided.

  When image data is sent to each LED head of the printer unit 30, each LED head exposes the photosensitive drum based on output image data described later, and an electrostatic latent image as a latent image is formed on the surface of the photosensitive drum. Form. When the developing device develops the electrostatic latent image to form a toner image as a developer image on the photosensitive drum, the transfer roller sequentially applies the toner images of the respective colors onto the paper fed from the paper cassette 111. The toner image is transferred to form a color toner image, and the fixing device fixes the color toner image on a sheet to form a color image. In this case, the scanner unit 20, the printer unit 30 and the like are external devices with respect to the control unit 12.

  The control unit 12 includes a RAM 13 as a first storage device including a volatile memory, a ROM 14 as a second storage device including a read-only memory, a CPU 15 as an arithmetic device, and the like. And the program recorded in the ROM 14 is executed.

  By the way, in the present embodiment, when the scanner unit 20 reads an image of a document, the color component of the background area of the document is removed, or the show-through that appears on the front surface through the image on the back side of the document is removed. You can do that.

  For this purpose, the control unit 12 receives input image data, generates output image data by performing correction processing on the input image data, and sends the output image data to the printer unit 30 via the output interface 16. send.

  Upon receiving the output image data sent from the control unit 12, the printer unit 30 extracts the image data of each color from the output image data and sends the image data of each color to the LED head.

  Next, the control block of the control unit 12 will be described.

  FIG. 1 is a control block diagram of a control unit in the first embodiment of the present invention.

  As shown in the figure, the control unit 12 includes an image input unit 51, an input image storage unit 52 as a first image storage unit, an image processing unit 40, an output image storage unit 53 as a second image storage unit, and An image output unit 54 is provided. The input image storage unit 52 records the input image data sent from the scanner unit 20, and the output image storage unit 53 forms the output image data sent to the printer unit 30 in the RAM 13, respectively. Is done.

  By the way, in the present embodiment, as described above, in order to remove the color component of the background area of the document or to remove the show-through that appears on the front surface of the image on the back side of the document, Correction processing is performed on the input image data recorded in the image storage unit 52.

  Therefore, a color space is converted for the input image data, a pixel after the color space is converted, that is, a pixel value of the input pixel, for example, a histogram of brightness values, is created, and a feature amount of the histogram is calculated, Based on the feature amount, parameters are set (derived) for removing the color component of the background area of the document or removing the show-through appearing on the front surface through the image on the back side of the document. Based on this, the correction process is performed on the input image data.

  In this case, if an attempt is made to create histograms for all input pixels, it is necessary to increase the storage capacity of the RAM 13 in order to record the histogram, so the histogram of the input image data recorded in the input image storage unit 52 is required. A histogram of input pixels sampled with a reduced number of samples by limiting the input image data used to create the image, decimating the input pixels, or limiting the input pixels based on pixel values Like to create.

  However, if the number of samplings is reduced, the feature amount cannot be calculated with high accuracy based on the histogram. Therefore, it becomes impossible to perform an appropriate correction process on the input image data.

  Therefore, it is determined whether or not the created histogram is valid. If the histogram is valid, a parameter is set based on the calculated feature amount, and the correction processing is performed on the input image data based on the parameter. Like to do.

  For this purpose, the image processing unit 40 includes an image reading unit 41, a sampling condition determination unit 42, a histogram creation unit 43, an effectiveness determination unit 44, a parameter derivation unit 45, an image correction unit 46, and an image writing unit 47. Calculations such as communication control, writing control, and image processing in each unit are performed by the CPU 15 (FIG. 3) in the control unit 12 using the RAM 13 as a working memory and executing a program recorded in the ROM 14. Is called.

  The image input unit 51 performs image input processing, acquires the input image data sent from the scanner unit 20 via the input interface 11, and writes the acquired input image data into the input image storage unit 52. ,Record. In the present embodiment, the image input unit 51 acquires the input image data sent from the scanner unit 20, but the input image data can be acquired from a host computer as a host device. It can be obtained from a storage medium such as a personal computer or HDD connected via a network, or from a portable storage medium such as a USB memory stick.

  The image reading unit 41 performs an image reading process, reads the input image data recorded in the input image storage unit 52 from the head of the input image storage unit 52, that is, one pixel at a time from the page head address, and reads the input image By converting a data color space (for example, RGB color space) into a predetermined color space (for example, CIE L * a * b color space), image data in the predetermined color space (hereinafter, “first converted image data”). Is sent to the sampling condition determination unit 42 and the histogram creation unit 43. The image reading unit 41 reads the input image data until the amount of data, that is, the size of the data reaches a first reading size necessary for creating a histogram, and the read input image data is a color space. When the conversion is performed, the reading of the input image data and the conversion of the color space are stopped. Here, the RGB color space is a color space in which the three primary colors of red, green, and blue are represented by value R, value G, and value B, respectively, and the CIEL * a * b color space is brightness, green, and magenta. And a color space represented by a mixture ratio of blue and yellow. Note that L represents a lightness value in a range of 0 to 100 [%], where 0 [%] is black and 100 [%] is white. Further, a is a mixing ratio of green and magenta. When the value is negative, green becomes stronger, and when the value is positive, magenta becomes stronger. And b is a mixture ratio of blue and yellow, and blue is strong at a negative value, and yellow is strong at a positive value.

  Further, when the image reading unit 41 receives a setting end signal, which will be described later, sent from the parameter deriving unit 45 and indicating that the parameter has been set, the image reading unit 41 again inputs the input image data recorded in the input image storage unit 52. One pixel is read from the page head address, the color space of the read input image data is converted, and first converted image data is generated and sent to the image correction unit 46. Subsequently, the image reading unit 41 reads the input image data until the size of the data reaches the second reading size set according to the amount of correction processing in the image correction unit 46, and the read input image When color space conversion is performed on data, reading of input image data and color space conversion are stopped.

  The sampling condition determination unit 42 performs a sampling condition determination process, reads the first converted image data from the image reading unit 41, and the input pixel of the first converted image data selects a pixel to create a histogram. It is determined whether or not sampling conditions, that is, sampling conditions are satisfied. The sampling condition determination unit 42 sets the sampling determination signal to 1 when the input pixel satisfies the sampling condition, and sets the sampling determination signal to 0 when the input pixel does not satisfy the sampling condition, and sends the sampling determination signal to the histogram creation unit 43.

  The histogram creation unit 43 performs a histogram creation process, and creates a histogram based on the input pixels determined to satisfy the sampling condition by the sampling condition determination unit 42. For this purpose, the histogram creation unit 43 receives the sampling determination signal sent from the sampling condition determination unit 42 and, when the sampling determination signal is 1, the first converted image data sent from the image reading unit 41. The pixel value of the input pixel, for example, the lightness value L is referred to, the frequency of the histogram in the pixel value is counted, and a histogram representing the frequency distribution corresponding to each pixel value is created. At this time, the histogram creation unit 43 counts the total number of pixels, which is the total value of the histogram frequencies, and does not count the histogram frequency and the total number of pixels when the sampling determination signal is 0.

  Further, when the histogram creating unit 43 creates a histogram for the input image data read until the first reading size is reached, the created histogram is recorded in the RAM 13.

  Then, the validity determination unit 44 performs a validity determination process, reads the total number of pixels of the histogram counted by the histogram creation unit 43, and determines whether the histogram is valid depending on whether the total number of pixels satisfies the validity condition. Judge whether. That is, when the total number of pixels in the histogram is equal to or greater than a predetermined threshold, the validity determination unit 44 determines that the histogram is valid as the validity condition is satisfied, and generates the validity determination signal as 1 (effective). When the total number of pixels in the histogram is less than the predetermined threshold, it is determined that the histogram is not valid because the validity condition is not satisfied, and the validity determination signal is set to 0 (invalid). Generated and sent to the parameter deriving unit 45.

  The parameter deriving unit 45 performs a parameter deriving process, refers to the histogram recorded in the RAM 13, and corrects the input image data based on the validity determination signal sent from the validity determining unit 44. Is sent to the image correction unit 46. At the same time, the parameter deriving unit 45 sets the setting end signal to 1 and sends it to the image reading unit 41 and the image writing unit 47. The setting end signal when the parameter is not set is set to zero.

  The image correction unit 46 performs image correction processing, and based on the parameters set by the parameter deriving unit 45, the color of the background area of the document with respect to the first converted image data sent from the image reading unit 41 Image data after performing correction processing such as background removal processing to remove components, and show-through removal processing to remove show-through that appears on the front side of the image on the back side of the document. (Hereinafter referred to as “second converted image data”) is generated and sent to the image writing unit 47.

  The image writing unit 47 performs an image writing process, receives the second converted image data from the image correction unit 46, generates output image data based on the setting end signal sent from the parameter deriving unit 45, Write to the output image storage unit 53. That is, when the setting end signal is 1, the image writing unit 47 uses the color space (for example, CIE L * a * b color space) of the second converted image data as the color space (for example, the printer unit 30). CMYBk color space) and the image data converted into the color space of the printer unit 30 is used as the output image data, and the output image storage unit pixel by pixel from the top of the output image storage unit 53, that is, from the page top address. 53 is written. When the setting end signal is 0, the image writing unit 47 does not generate output image data. The CMYBk color space is a color space in which each color of cyan, magenta, yellow, and black is represented by value C, value M, value Y, and value Bk.

  The image output unit 54 performs image output processing, reads output image data from the output image storage unit 53, and sends it to the printer unit 30 via the output interface 16 (FIG. 3). When receiving the output image data, the printer unit 30 forms an image on a sheet based on the output image data as described above.

  In the present embodiment, output image data is sent to the printer unit 30, but the output image data is sent to a host computer, a personal computer connected via a network, an HDD, or the like. It can be sent to a storage medium or can be sent to a portable storage medium such as a USB memory stick. Furthermore, output image data can be sent to a monitor.

  Next, the sampling condition determination unit 42 will be described.

  FIG. 4 is a control block diagram of the sampling condition determination unit in the first embodiment of the present invention.

  As shown in the figure, the sampling condition determination unit 42 includes a thinning determination unit 42a, a threshold determination unit 42b, and a comprehensive determination unit 42c.

  The thinning determination unit 42a determines at which coordinates on the image plane the input pixel is located, and determines whether the input pixel satisfies the first condition based on the coordinates at which the input pixel is located. Judgment is made based on whether or not the pixel is a pixel to be thinned out based on the parameter, that is, whether the pixel is not a thinning target pixel. When the thinning determination unit 42a determines that the input pixel is not the thinning target pixel and satisfies the first condition, the thinning determination unit 42a sets the first determination signal to 1 and sends it to the comprehensive determination unit 42c, and the input pixel is the thinning target pixel. If it is determined that the first condition is not satisfied, the second determination signal is set to 0 and sent to the comprehensive determination unit 42c.

  The threshold determination unit 42b refers to the pixel value of the input pixel, and determines whether the pixel value satisfies the second condition by whether it falls within a preset effective range. When the threshold value determination unit 42b determines that the pixel value falls within the effective range and satisfies the second condition, the threshold value determination unit 42b sets the second determination signal to 1 and sends it to the comprehensive determination unit 42c, and the pixel value falls within the effective range. If it does not fit and it is determined that the second condition is not satisfied, the second determination signal is set to 0 and sent to the comprehensive determination unit 42c.

  Whether the comprehensive determination unit 42c satisfies the first and second conditions by taking the logical product (AND) of the first and second determination signals sent from the thinning determination unit 42a and the threshold determination unit 42b. When the first and second conditions are satisfied, the sampling condition is determined to be satisfied, the sampling determination signal is set to 1, and at least one of the first and second conditions is not satisfied Then, it is determined that the sampling condition is not satisfied, and the sampling determination signal is set to zero.

  In the present embodiment, two determination items by the thinning determination unit 42a and the threshold determination unit 42b are set as determination items for determining whether or not the sampling condition is satisfied, and the first and second conditions are set as follows. When satisfied, the sampling condition is determined to be satisfied. However, if one determination item is set and one of the first and second conditions is satisfied, the sampling condition is satisfied. It can be judged. Three or more determination items can be set.

  Next, the parameter deriving unit 45 will be described.

  FIG. 5 is a control block diagram of the parameter deriving unit in the first embodiment of the present invention.

  As shown in the figure, the parameter deriving unit 45 includes a feature amount calculating unit 45a and a parameter setting unit 45b for setting parameters.

  The feature quantity calculation unit 45a refers to the histogram recorded in the RAM 13 (FIG. 3), and the feature value of the histogram, in this embodiment, a lightness value L for removing the color component of the background area of the document. The threshold value Lth is calculated. Then, the parameter setting unit 45b determines whether or not the validity determination signal sent from the validity determination unit 44 is 1, and when the validity determination signal is 1, the parameter setting unit 45b calculates by the feature amount calculation unit 45a. The threshold value Lth of the brightness value L is read, and a setting conversion table as a first parameter is set based on the threshold value Lth. When the validity determination signal sent from the validity determination unit 44 is 0, the parameter setting unit 45b sets a general-purpose conversion table as a second parameter set in advance. Then, the parameter setting unit 45 b sets the setting conversion table or the general-purpose conversion table, and simultaneously generates a setting end signal as 1 and sends it to the image reading unit 41 and the image writing unit 47.

  Next, the operation of the MFP 10 having the above-described configuration will be described.

  In this case, background removal processing for removing the color component of the background area of the document based on the histogram created using the lightness value L as the pixel value of the first converted image data will be described.

  FIG. 6 is a first flowchart showing the operation of the multifunction device in the first embodiment of the present invention. FIG. 7 is a second flowchart showing the operation of the multifunction device in the first embodiment of the present invention. FIG. 9 is a diagram for explaining the pixel to be thinned out in the first embodiment of the present invention, FIG. 9 is a diagram showing an example of a histogram frequency distribution in the first embodiment of the present invention, and FIG. FIG. 11 is a diagram illustrating an example of a setting conversion table according to the first embodiment, and FIG. 11 is a diagram illustrating an example of a general-purpose conversion table according to the first embodiment of the present invention. 9, the horizontal axis represents the lightness value L, the vertical axis represents the frequency G (L), and in FIGS. 10 and 11, the horizontal axis represents the lightness value Li on the input side, and the vertical axis represents the lightness value Li on the output side. The brightness value Lo is taken.

  First, the image input unit 51 acquires the input image data sent from the scanner unit 20 via the input interface 11 and writes the acquired input image data in the input image storage unit 52.

  Subsequently, the image reading unit 41 initializes the reading position in the input image storage unit 52 to set the page head address.

  In this case, the image reading unit 41 reads the input image data line by line in the main scanning direction, and sequentially changes the line to be read in the sub scanning direction every time reading of one line is completed.

The size of the input image data in the main scanning direction, that is, the image width is W, the size in the sub-scanning direction, that is, the image height is H, and the input pixel corresponding to the page head address of the input image data to be read When the first coordinate of the coordinate (x, y) is (0, 0), the coordinate (x, y) of the input pixel when the readout position is initialized is
x = 0
y = 0
And the coordinates of the pixel of the nth pixel (0 ≦ n ≦ (W−1) * (H−1)) are (x _n , y _n ), and x _n is expressed by a remainder of n / W, y _n is represented by a quotient of n / W.

  In this case, the image reading unit 41 reads the input image data of the background area in which the image of characters, figures, etc. is not formed in the original document among the input image data recorded in the input image storage unit 52. Therefore, the image height H is set in accordance with the read input image data.

Next, the image reading unit 41 reads the input image data recorded in the input image storage unit 52 pixel by pixel from the page head address, and the color space of the read input image data, in this embodiment, the RGB color space Is converted into a predetermined color space, in this embodiment, a CIEL * a * b color space, and the first converted image data converted into the CIEL * a * b color space is converted into a sampling condition determination unit 42 and a histogram. The data is sent to the creation unit 43. In this case, input image data of the nth pixel, that is, RGB data (R _n , G _n , B _n ) is read, the color space is converted, and the CIE L * a * b data (L _n , a _n , b) _n ) is the first converted image data.

  Subsequently, in the sampling condition determination unit 42, the thinning determination unit 42a reads the first converted image data and determines whether the input pixel is not a thinning target pixel. When the input pixel is not a thinning target pixel, the threshold determination unit 42b determines whether or not the pixel value of the input pixel falls within the preset effective range of the pixel value. When the pixel value of the input pixel falls within the effective range of the pixel value set in advance, the comprehensive determination unit 42c sets the sampling determination signal to 1.

  On the other hand, when the input pixel is a pixel to be thinned out or the pixel value of the input pixel does not fall within the effective range of the preset pixel value, the comprehensive determination unit 42c sets the sampling determination signal to 0.

In the present embodiment, as shown in FIG. 8, for example, in input image data having an image width W of 8 and an image height H of 8, the sampling interval xi in the main scanning direction is set to 4, When the sampling interval yi in the sub-scanning direction is set to 2, the remainder of x _n / xi is 0 with respect to the coordinates (x _n , y _n ) of the input pixel, and y _n / y i For a pixel whose remainder is 0, for example, the pixel q1 in FIG. 8, the thinning determination unit 42a determines that the pixel is not a thinning target pixel, and the remainder of x _n / xi is not 0 or the remainder of y _n / yi is 0. For a pixel that is not, for example, the pixel q2 in FIG. 8, the thinning determination unit 42a determines that the pixel is a thinning target pixel.

Further, for example, for the pixel value (L _n , a _n , b _n ) of the nth pixel, the maximum value of each effective range is set to L _max , a _max , b _max , and the minimum value is L _min , a _min , B _min, and when only the high brightness / low chroma region is the effective range, the maximum values L _max , a _max , b _max and the minimum values L _min , a _min , b _min are
L _max = 100
L _min = 80
a _max = 5
a _min = -5
b _max = 5
b _min = -5
Set to

Then, the threshold determination unit 42b refers to the pixel values (L _n , a _n , b _n ) of the _nth pixel, and the pixel values L _n , a _n , b _n are
L _min ≦ L _n ≦ L _max
And
a _min ≦ a _n ≦ a _max
And
b _min ≦ b _n ≦ b _max
The pixel values (L _n , a _n , b _n ) are determined to be within the effective range, and the pixel values L _n , a _n , b _n are
L _min ≦ L _n ≦ L _max
Or
a _min ≦ a _n ≦ a _max
Or
b _min ≦ b _n ≦ b _max
If not, it is determined that the pixel value (L _n , a _n , b _n ) does not fall within the effective range.

  Next, the histogram creation unit 43 receives the sampling determination signal sent from the sampling condition determination unit 42 and, when the sampling determination signal is 1, the first converted image data sent from the image reading unit 41. Pixel value, in the present embodiment, the brightness value L is referred to, and the histogram frequency (L) at the brightness value L is counted. That is, the histogram creation unit 43 increments the frequency G (L) for each lightness value L. Further, when the sampling determination signal is 1, the histogram creation unit 43 counts the total number of pixels Nq of the histogram, and when the sampling signal is 0, the histogram creation unit 43 does not count the histogram frequency G (L) and the total number of pixels Nq. .

The image reading unit 41 determines whether the size Z of the input image data read from the input image storage unit 52 is smaller than the first read size Z1, and the size Z of the input image data is the first read size. If smaller than Z1, the reading position of the input image data is incremented, the next input image data is read, the color space of the read input image data is converted, and the first converted image data is converted into the sampling condition determination unit 42 and the histogram. The data is sent to the creation unit 43. In this case, the size Z of the input image data and the first read size Z1 are both expressed by the number of pixels, and the first read size Z1 is a value for 256 lines that is the image height H, that is,
Z1 = W × 256
To be.

  Subsequently, the histogram creation unit 43 receives the sampling determination signal sent from the sampling condition determination unit 42, and when the sampling determination signal is 1, refers to the lightness value L of the first converted image data, The frequency (L) of the histogram at the lightness value L is counted, and the total number of pixels Nq of the histogram is counted.

  In this way, the histogram creation unit 43 refers to the lightness value L of the input pixel of the first converted image data for the input image data read until the first read size Z1 is reached. A histogram representing the distribution of the frequency G (L) for each lightness value L as shown in FIG. 9 is created and recorded in the RAM 13.

  When the size Z of the input image data read by the image reading unit 41 from the input image storage unit 52 becomes equal to the first reading size Z1, the validity determination unit 44 sends the total number of pixels of the histogram from the histogram creation unit 43. Nq is read out, and whether or not the total pixel number Nq satisfies the effective condition is determined based on whether or not the total pixel number Nq is equal to or greater than the threshold value Nth.

In the present embodiment, the threshold value Nth is set to a predetermined ratio of the first read size Z1, in this embodiment, 20%, and the total number of pixels Nq is
Nq ≧ Nth
= Z1 × 0.2
The validity determination unit 44 determines that the total number of pixels Nq satisfies the validity condition and the histogram is valid, sets the validity determination signal to 1, and the total number of pixels Nq is
Nq <Nth
= Z1 × 0.2
In this case, the validity determination unit 44 determines that the total number of pixels Nq does not satisfy the validity condition and the histogram is not valid, sets the validity determination signal to 0, and sends it to the parameter deriving unit 45.

  Subsequently, the parameter derivation unit 45 reads the validity determination signal, and when the validity determination signal is 1, the feature amount calculation unit 45a refers to the histogram sent from the histogram creation unit 43, and the brightness of the histogram A threshold value Lth of the value L is calculated.

For this purpose, the feature amount calculation unit 45a sequentially reads the frequency G (L) from the side with the lightness value L from the high (L = 100) side to the low (L = 0) side in the histogram.
G (L)> G (L + 1)
The lightness value L that becomes is the peak start lightness value Ls, and first G (L-1)> G (L)
The lightness value L that becomes is the peak lightness value Lp.

Incidentally, since the lightness value L of the background area of the document generally has a frequency distribution that is substantially normal with the peak lightness value Lp as the center, the feature amount calculation unit 45a removes the color component of the background area of the document. Threshold value Lth of brightness value L for
Lth = Lp− (Ls−Lp)
Is calculated.

  Next, the parameter setting unit 45b of the parameter deriving unit 45 sets as shown in FIG. 10 for removing the color component of the background area of the document based on the threshold value Lth calculated by the feature amount calculation unit 45a. A conversion table is set, and simultaneously, a setting end signal is set to 1 and sent to the image reading unit 41 and the image writing unit 47. The setting conversion table is set in correspondence with the input side of the image correction unit 46 represented by 0 to 100, that is, the lightness value Li and the lightness value Li before conversion, and is represented by 0 to 100. In addition, when the output value of the image correction unit 46, that is, the lightness value Lo after conversion and the lightness value Li is less than a predetermined value Lf (for example, 50), as shown by a line f1 in FIG. The lightness value Lo is equal to the lightness value Li. When the lightness value Li is equal to or greater than the threshold value Lth, the lightness value Lo is set to 100 regardless of the magnitude of the lightness value Li, as indicated by the line f2. Further, when the lightness value Li is not less than the value Lf and less than the threshold value Lth, the point at which the lightness value Li in the line f1 becomes the value Lf is defined as pt1, and the point where the lightness value Li in the line f2 becomes the threshold value Lth. When pt2 is set, the lightness value Lo is set to a value on the line f3 connecting the points pt1 and pt2.

  As a result, the lightness value Li gradually increases as shown by the line f3 as the value Lf changes from the value Lf to the threshold value Lth. No jumping occurs.

  When the validity determination signal is 0, the parameter setting unit 45b sets a preset general-purpose conversion table, and simultaneously generates a setting end signal as 1, thereby generating the image reading unit 41 and the image writing unit. Send to 47. In the present embodiment, in the general-purpose conversion table, as shown in FIG. 11, the lightness value Li on the input side is equal to the lightness value Lo on the output side. Accordingly, the lightness value Li and the lightness value Lo can be made different.

  When the image reading unit 41 receives the setting end signal, the image reading unit 41 inputs again to perform correction processing on the input image data based on the setting conversion table or the general-purpose conversion table set by the parameter setting unit 45b. The read position in the image storage unit 52 is initialized to the page head address. Also, upon receiving the setting end signal, the image writing unit 47 initializes the writing position for writing the output image data after the correction processing is performed in the output image storage unit 53 to obtain the page head address. .

That is, the coordinates (x, y) when the reading position and the writing position are initialized are:
x = 0
y = 0
To be.

Next, the image reading unit 41 reads the input image data recorded in the input image storage unit 52 pixel by pixel from the page head address, and converts the RGB color space of the read input image data into the CIE L * a * b color space. To the image correction unit 46. In this case, input image data of the nth pixel, that is, RGB data (R _n , G _n , B _n ) is read, the color space is converted, and the CIE L * a * b data (L _n , a _n , b) _n ) is converted into first converted image data and sent to the image correction unit 46.

  Subsequently, when the image correction unit 46 receives the first converted image data, the image correction unit 46 performs image correction processing, refers to the setting conversion table set in the parameter derivation unit 45, and determines the lightness L in the first converted image data. Is converted by the lightness value Li and the lightness value Lo to perform the background removal processing correction processing, and the second converted image data after the correction processing is sent to the image writing section 47.

The image writing unit 47 receives the second converted image data sent from the image correcting unit 46, generates output image data based on the setting end signal sent from the parameter deriving unit 45, and outputs an output image storage unit. 53 is written. That is, when the setting end signal is 1, the image writing unit 47 converts the CIE L * a * b color space of the second converted image data into the CMYBk color space of the printer unit 30 and converts it into the CMYBk color space. The converted image data is used as the output image data, and is written into the output image storage unit 53 pixel by pixel from the page head address. In this case, the second converted image data of the nth pixel, that is, CIE L * a * b data (L _n , a _n , b _n ) is read, the color space is converted, and CMYBk data (C _n , M _n , Y _n, Bk _n) is the output image data, it is recorded in the output image storage unit 53. When the setting end signal is 0, the image writing unit 47 does not generate output image data.

  The image reading unit 41 determines whether the size Z of the input image data read from the input image storage unit 52 is smaller than the second reading size Z2, and the size Z of the input image data is the second reading size. If smaller than Z2, the read position of the input image data is incremented, the next input image data is read, the color space of the read input image data is converted, and the first converted image data is sent to the image correction unit 46. Upon receiving the first converted image data, the image correcting unit 46 performs correction processing, and converts the lightness L in the first converted image data between the lightness value Li and the lightness value Lo, thereby performing background removal processing. The second converted image data after the background removal processing is performed is sent to the image writing unit 47.

  Further, the image writing unit 47 converts the color space of the second converted image data, increments the writing position of the output image data, and writes the output image data in the output image storage unit 53.

  When the size Z of the input image data read by the image reading unit 41 from the input image storage unit 52 becomes equal to the second reading size Z2, the image output unit 54 sends the output image data to the printer unit 30 via the output interface 16. . Upon receiving the output image data sent from the control unit 12, the printer unit 30 extracts the image data of each color from the output image data and sends the image data of each color to the LED head.

In this case, the second read size Z2 is Z2 = W × H
To be.

Next, a flowchart will be described.
Step S1: The image input unit 51 acquires input image data.
Step S2: The image reading unit 41 initializes the reading position.
Step S3 The image reading unit 41 reads input image data and converts the color space.
Step S4: The thinning determination unit 42a determines whether the input pixel is not a thinning target pixel. If the input pixel is not a thinning target pixel, the process proceeds to step S5. If the input pixel is a thinning target pixel, the process proceeds to step S7.
Step S5: The threshold determination unit 42b determines whether or not the pixel value of the input pixel is within the effective range. If the pixel value of the input pixel falls within the valid range, the process proceeds to step S6. If the pixel value of the input pixel does not fall within the valid range, the process proceeds to step S7.
Step S6: The overall judgment unit 42c sets the sampling judgment signal to 1.
Step S7: The comprehensive judgment unit 42c sets the sampling judgment signal to 0.
Step S8: The histogram creation unit 43 determines whether or not the sampling determination signal is 1. If the sampling signal is 1, the process proceeds to step S9. If the sampling signal is not 1, the process proceeds to step S10.
Step S9 The histogram creation unit 43 counts the histogram frequency G (L) and counts the total number of pixels Nq of the histogram.
Step S10: The image reading unit 41 determines whether the size Z of the input image data is smaller than the first reading size Z1. If the size Z of the input image data is smaller than the first readout size Z1, the process proceeds to step S11. If the size Z of the input image data is greater than or equal to the first readout size Z1, the process proceeds to step S12.
Step S11 The image reading unit 41 increments the reading position and returns to step S3.
Step S12: The parameter deriving unit 45 determines whether or not the validity determination signal is 1. If the validity determination signal is 1, the process proceeds to step S13. If the validity determination signal is not 1, the process proceeds to step S15.
Step S13: The feature amount calculation unit 45a calculates a feature amount.
Step S14: The parameter setting unit 45b sets a setting conversion table.
Step S15 The parameter setting unit 45b sets a general-purpose conversion table.
Step S16 The image reading unit 41 initializes the reading position, and the image writing unit 47 initializes the writing position.
Step S17 The image reading unit 41 reads input image data and converts the color space.
Step S18 The image correction unit 46 performs image correction processing.
Step S19 The image writing unit 47 converts the color space and writes the output image data.
Step S20: The image reading unit 41 determines whether the size Z of the input image data is smaller than the second reading size Z2. If the size Z of the input image data is smaller than the second readout size Z2, the process proceeds to step S21. If the size Z of the input image data is greater than or equal to the second readout size Z2, the process proceeds to step S22.
Step S21 The image reading unit 41 increments the reading position, the image writing unit 47 increments the writing position, and the process returns to step S17.
Step S22: The image output unit 54 generates output image data and ends the process.

  As described above, in the present embodiment, it is determined whether the histogram created by the histogram creating unit 43 is valid, and when the histogram is valid, the parameter is set by the parameter deriving unit 45, and the parameter is set. Since the first converted image data is corrected based on the above, the parameters can be calculated with high accuracy based on the histogram. Therefore, an appropriate correction process can be performed on the input image data.

  When the histogram is not valid, the general-purpose conversion table is set as a parameter, so that the image correction process in the image correction unit 46 can be simplified.

  Next, image quality when the background removal processing is performed when the total number of pixels Nq in the histogram is smaller than the threshold value Nth and the total number of pixels Nq does not satisfy the valid condition will be described.

  12 shows an example of input image data when the total number of pixels in the histogram is small, FIG. 13 shows an example of output image data when the total number of pixels in the histogram is small, and FIG. 14 shows the total number of pixels in the histogram. It is a figure which shows the example of the histogram produced when is small. In FIG. 14, the lightness value L is taken on the horizontal axis, and the frequency G (L) is taken on the vertical axis.

  In this case, a case will be described in which the color component of the background area of the document is not white, but is composed of high brightness / low saturation color and low brightness / high saturation color.

  In FIG. 12, Di is input image data. In this case, the input image data Di has an image width of 12, an image height of 6, and a sampling interval in the main scanning direction and a sampling interval in the sub-scanning direction. Both are set to 2.

  In this case, the hatched pixels dz1 to dz4 in the drawing are pixels that form a base region with colors of low brightness and high saturation, and the pixels dz5 to dz8 that are shaded in the drawing are highly bright. This is a pixel that forms a base region with a color of low and low saturation. In addition, pixels dz3, dz4, dz7, dz8, etc. in which a circle is drawn in a rectangle on the drawing are pixels that are not to be thinned out, that is, non-thinning target pixels, and a circle is drawn in the rectangle on the drawing. Pixels dz1, dz2, dz5, dz6, etc. that are not present are thinning target pixels.

  By the way, in the present embodiment, the thinning determination unit 42a determines that the input pixel is not a thinning target pixel, and the threshold determination unit 42b determines that the pixel value of the input pixel falls within the preset effective range. In this case, the sampling determination signal is set to 1 in the overall determination unit 42c, and the histogram generation unit 43 generates a histogram.

  Here, only when the input pixel is determined not to be a thinning target pixel by the thinning determination unit 42a and the input pixel is a pixel having high brightness and low saturation, the threshold value determination unit 42b performs the pixel value of the input pixel. Is determined to fall within the preset effective range, the sampling determination signal is set to 1 in the overall determination unit 42c because a pixel is added with a mesh in the drawing and a circle is drawn in a rectangle Only dz7, dz8, etc.

  In that case, the frequency distribution of the histogram formed by the histogram creation unit 43 based on the pixels dz7, dz8, etc. in which the sampling determination signal is set to 1 is as shown in FIG. 14, and the peak lightness value Lp and its vicinity The frequency G (L) at the lightness value L of the histogram becomes extremely small, and accordingly, the total number of pixels Nq of the histogram also becomes small.

  In this state, the validity determination unit 44 temporarily determines that the histogram is valid, and the parameter derivation unit 45 calculates the threshold value Lth of the lightness value L with reference to the histogram shown in FIG. When the parameter setting unit 45b sets the setting conversion table as shown in FIG. 10, only the high and low chroma pixels dz7, dz8, etc. whose input side lightness value Li is greater than or equal to the threshold value Lth are output. The brightness value Lo on the side is set to 100, which is the same as white.

  As a result, output image data Do as shown in FIG. 13 is generated.

  In FIG. 13, Do is output image data, the image width of the output image data Do is 12, the image height is 6, and the sampling interval in the main scanning direction and the sampling interval in the sub-scanning direction are both 2. Set to The pixels dz1 'to dz8' of the output image data Do correspond to the pixels dz1 to dz8 of the input pixel data Di.

  In this case, the histogram of FIG. 14 is created only by the pixels dz7, dz8, etc., and only the high-lightness / low-saturation pixels dz5 to dz8 whose input-side lightness value Li is greater than or equal to the threshold value Lth are output-side lightness values Lo. Is set to 100, the same as white, and color components are removed from the pixels dz5 ′ to dz8 ′ and the like of the output image data Do.

  However, for the pixels dz1 to dz4 and the like that form the background region with the low brightness and high saturation colors of the input pixel data Di, the output side brightness value Lo is made equal to the input side brightness value Li, so that the output image data Do The color components are not removed in the pixels dz1 ′ to dz4 ′.

  In this case, if an image is formed on a sheet based on the output image data Do, the color of the base region changes greatly.

  On the other hand, in the present embodiment, as shown in FIG. 14, when the histogram is created by only the pixels dz7, dz8, etc., the total number of pixels Nq of the histogram is smaller than the threshold value Nth, Since the number Nq does not satisfy the effective condition, the background removal process is not performed.

  Next, a second embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st Embodiment, the same code | symbol is provided and the effect of the same embodiment is used about the effect of the invention by having the same structure.

  FIG. 15 is a control block diagram of the control unit according to the second embodiment of the present invention.

  In this case, a control signal control unit 48 is provided in the image processing unit 40.

  Then, the image reading unit 41 reads the input image data recorded in the input image storage unit 52 as the first image storage unit pixel by pixel from the page head address, and reads the color space (for example, RGB) of the read input image data Color space) is converted into a predetermined color space (for example, CIE L * a * b color space), and the first converted image data, which is image data converted into the predetermined color space, is sampled by the sampling condition determining unit 42 and the histogram. The data is sent to the creation unit 43 and the image correction unit 46.

  The image reading unit 41 starts reading the input image data, continues reading the input image data, or stops reading the input image data in accordance with the control signal sent from the control signal control unit 48. The reading is resumed from the position where the reading of the input image data is stopped.

  The image correction unit 46 corrects the first converted image data sent from the image reading unit 41 based on the general-purpose conversion table as the initial parameter specified in advance and as the second parameter, and performs correction. The second converted image data, which is the processed image data, is sent to the image writing unit 47.

  The image writing unit 47 converts the second converted image data sent from the image correcting unit 46 into a color space (for example, CMYBk color space) of the output device to generate output image data, and a page head address To the output image storage unit 55 pixel by pixel. Then, in accordance with the control signal sent from the control signal control unit 48, the reading of the output image data is started, the writing of the output image data is continued, the writing of the output image data is stopped, and the writing of the output image data is performed. To resume writing from the position where is stopped.

  In addition, the control signal control unit 48 performs control signal control processing, and the image reading unit 41 performs input image processing based on the validity determination signal from the validity determination unit 44 and the setting end signal from the parameter derivation unit 45. In the image writing unit 47, the reading of the data is started, the reading of the input image data is continued, the reading of the input image data is stopped, the reading is restarted from the position where the reading of the input image data is stopped, Control to start writing output image data, continue writing output image data, stop writing output image data, and resume writing from the position where writing of output image data was stopped Generate a signal.

  Next, the operation of the multifunction machine 10 as the image processing apparatus having the above configuration will be described.

  In this case, as in the first embodiment, based on the histogram created using the lightness value L as the pixel value of the first converted image data, the color component in the background area of the document is removed. The background removal process will be described.

  FIG. 16 is a first flowchart showing the operation of the multifunction machine according to the second embodiment of the present invention, and FIG. 17 is a second flowchart showing the operation of the multifunction machine according to the second embodiment of the present invention.

  First, the image input unit 51 acquires the input image data sent from the scanner unit 20 via the input interface 11 and writes the acquired input image data in the input image storage unit 52.

Subsequently, the control signal control unit 48 generates a start signal as an initial value of the control signal and sends it to the image reading unit 41 and the image writing unit 47. The image reading unit 41 receives the start signal sent from the control signal control unit 48, initializes the reading position in the input image storage unit 52, and sets it as the page head address. The coordinates (x, y) of the input pixel when the readout position is initialized are:
x = 0
y = 0
become. The image writing unit 47 receives the start signal sent from the control signal control unit 48, initializes the writing position in the output image storage unit 53, and sets it as the page head address. The coordinates (x, y) of the output pixel when the writing position is initialized are:
x = 0
y = 0
become.

  Next, the parameter setting unit 45b of the parameter deriving unit 45 sets a general-purpose conversion table as shown in FIG. 11 as an initial parameter.

Subsequently, the image reading unit 41 reads the input image data recorded in the input image storage unit 52 pixel by pixel from the page head address, and converts the RGB color space of the read input image data into the CIEL * a * b color space. The first converted image data converted into the CIE L * a * b color space is sent to the sampling condition determination unit 42, the histogram creation unit 43, and the image correction unit 46. In this case, input image data of the nth pixel, that is, RGB data (R _n , G _n , B _n ) is read, the color space is converted, and the CIE L * a * b data (L _n , a _n , b) _n ) is the first converted image data.

  Subsequently, the sampling condition determination unit 42 performs sampling condition determination processing, and the histogram creation unit 43 performs histogram creation processing based on the determination result of the sampling condition determination unit 42. At this time, the image correction unit 46 performs image correction processing. Is performed by parallel processing. That is, steps S35 to S40 and steps S41 to S42 in FIG. 16 are performed in parallel.

  In this case, in the sampling condition determination unit 42, the thinning determination unit 42a (FIG. 4) reads the first converted image data, and determines whether the input pixel is not a thinning target pixel in the same manner as in the first embodiment. Judging. When the input pixel is not the pixel to be thinned out, the threshold determination unit 42b determines whether the pixel value of the input pixel falls within the effective range of the pixel value set in advance by the same method as in the first embodiment. . When the pixel value of the input pixel falls within the effective range of the pixel value set in advance, the comprehensive determination unit 42c sets the sampling determination signal to 1.

  On the other hand, when the input pixel is a pixel to be thinned out or the pixel value of the input pixel does not fall within the effective range of the preset pixel value, the comprehensive determination unit 42c sets the sampling determination signal to 0.

  Next, the histogram creation unit 43 receives the sampling determination signal sent from the sampling condition determination unit 42 and, when the sampling determination signal is 1, the first converted image data sent from the image reading unit 41. Pixel value, in the present embodiment, the brightness value L is referred to, and the histogram frequency (L) at the brightness value L is counted. That is, the histogram creation unit 43 increments the frequency G (L) for each lightness value L. Further, when the sampling determination signal is 1, the histogram creation unit 43 counts the total number of pixels Nq of the histogram, and when the sampling signal is 0, the histogram creation unit 43 does not count the histogram frequency G (L) and the total number of pixels Nq. .

  On the other hand, when receiving the first converted image data sent from the image reading unit 41, the image correcting unit 46 refers to the general conversion table set in the parameter setting unit 45b of the parameter deriving unit 45, and The converted image data is corrected, and the second converted image data that is the corrected image data is sent to the image writing unit 47. In the general-purpose conversion table, as shown in FIG. 11, the lightness value Li on the input side and the lightness value Lo on the output side are made equal, so the first converted image data is directly used as the second converted image data. become.

Subsequently, the image writing unit 47 converts the CIEL * a * b color space of the second converted image data into the CMYBk color space of the printer unit 30 as an output device, and converts it into the color space of the printer unit 30. The processed image data is used as the output image data, and is written into the output image storage unit 53 pixel by pixel from the page head address. In this case, the first converted image data of the nth pixel, that is, CIE L * a * b data (L _n , a _n , b _n ) is read, the color space is converted, and CMYBk data (C _n , M _n , Y _n, Bk _n) is generated as output image data, is recorded in the output image storage unit 53.

In this manner, the sampling condition determination process is performed by the sampling condition determination unit 42, the histogram generation process is performed by the histogram generation unit 43 based on the determination result of the sampling condition determination unit 42, and the image correction unit 46 performs image correction. While the processing is performed by parallel processing, the image reading unit 41 determines whether the size Z of the input image data read from the input image storage unit 52 is smaller than the first reading size Z1, and the input image When the data size Z is smaller than the first read size Z1, the control signal control unit 48 generates a continuation signal as a control signal for continuing the reading of the input image data, sends it to the image reading unit 41, and outputs the output image. A continuation signal is generated as a control signal for continuing the data writing and is sent to the image writing unit 47. Thereby, the image reading unit 41 increments the reading position of the input image data, reads the next input image data, converts the color space of the read input image data, and determines the first converted image data as a sampling condition determination Sent to the unit 42, the histogram creation unit 43, and the image correction unit 46. Further, the image writing unit 47 converts the color space of the second converted image data, increments the writing position of the output image data, and writes the output image data in the output image storage unit 53. In this case, the size Z of the input image data and the first readout size Z1 are both expressed by the number of pixels, and the first readout size Z1 is a value for 256 lines, that is,
Z1 = W × 256
To be.

  When the size Z of the input image data read from the input image storage unit 52 by the image reading unit 41 becomes equal to the first reading size Z1, the control signal control unit 48 controls the control signal to stop reading the input image data. Is generated and sent to the image reading unit 41, and a stop signal is generated and sent to the image writing unit 47 as a control signal for stopping the writing of the output image data. Thereby, the image reading unit 41 stops reading the input image data, and the image writing unit 47 stops writing the output image data.

  Subsequently, the validity determination unit 44 refers to the total number of pixels Nq of the histogram sent from the histogram creation unit 43, and the total number of pixels Nq satisfies the validity condition depending on whether the total number of pixels Nq is equal to or greater than the threshold value Nth. Judge whether to meet.

In the present embodiment, the threshold value Nth is set to a value of 20% of the first read size Z1, and the total number of pixels Nq is
Nq ≧ Nth
= Z1 × 0.2
In this case, the validity determination unit 44 determines that the total number of pixels Nq satisfies the validity condition and that the histogram is valid, generates a validity determination signal as 1, and sends it to the parameter deriving unit 45. The total number of pixels Nq is
Nq <Nth
= Z1 × 0.2
In this case, the validity determination unit 44 determines that the total number of pixels Nq does not satisfy the validity condition and the histogram is not valid, generates the validity determination signal as 0, and sends it to the control signal control unit 48.

  Thus, the control signal control unit 48 immediately generates a restart signal as a control signal for restarting reading of the input image data, sends it to the image reading unit 41, and restarts as a control signal for restarting writing of the output image data. A signal is generated and sent to the image writing unit 47. The image reading unit 41 receives the restart signal sent from the control signal control unit 48 and resumes reading from the position where the reading is stopped, and the image writing unit 47 sends the restart signal sent from the control signal control unit 48. The writing is resumed from the position where the writing was stopped.

  Also, the parameter deriving unit 45 reads the validity determination signal, and when the validity determination signal is 1, the feature amount calculation unit 45a (FIG. 5) refers to the histogram sent from the histogram creation unit 43, and the histogram The threshold value Lth of the lightness value L is calculated.

  Next, the parameter setting unit 45b of the parameter deriving unit 45 removes the color component of the background area of the document based on the threshold value Lth calculated by the feature amount calculation unit 45a, as shown in FIG. A setting conversion table as a parameter of 1 is set, and at the same time, a setting end signal is set to 1 and generated and sent to the control signal control unit 48.

  The control signal control unit 48 receives the setting end signal sent from the parameter deriving unit 45, generates a start signal as a control signal for starting the reading of the input image data from the page head address, and generates an image reading unit. 41.

  When the image reading unit 41 receives the start signal sent from the control signal control unit 48, the image reading unit 41 initializes the reading position in the input image storage unit 52 to be the page head address. Further, when the image writing unit 47 receives the start signal sent from the control signal control unit 48, the image writing unit 47 initializes the writing position for writing the output image data in the output image storage unit 53 and sets it as the page head address.

That is, the coordinates (x, y) of the input pixel when the reading position and the writing position are initialized are:
x = 0
y = 0
To be.

Next, the image reading unit 41 reads the input image data recorded in the input image storage unit 52 pixel by pixel from the page head address, and converts the RGB color space of the read input image data into the CIE L * a * b color space. To the image correction unit 46. In this case, input image data of the nth pixel, that is, RGB data (R _n , G _n , B _n ) is read, the color space is converted, and the CIE L * a * b data (L _n , a _n , b) _n ) becomes the first converted image data and is sent to the image correction unit 46.

  Subsequently, when the image correction unit 46 receives the first converted image data, the image correction unit 46 refers to the setting conversion table set in the parameter derivation unit 45 and converts the lightness L in the first converted image data. The background conversion process is corrected, and the second converted image data after the correction process is sent to the image writing unit 47.

The image writing unit 47 receives the second converted image data sent from the image correction unit 46, receives the start signal sent from the control signal control unit 48, generates output image data, and stores the output image data. Write to part 53. That is, when receiving the start signal, the image writing unit 47 converts the CIEL * a * b color space of the second converted image data into the CMYBk color space of the printer unit 30, and the image converted into the CMYBk color space. Data is used as the output image data, and is written into the output image storage unit 53 pixel by pixel from the page head address. In this case, the second converted image data of the nth pixel, that is, CIE L * a * b data (L _n , a _n , b _n ) is read, the color space is converted, and CMYBk data (C _n , M _n , Y _n, Bk _n) is the output image data, it is recorded in the output image storage unit 53.

  The image reading unit 41 determines whether the size Z of the input image data read from the input image storage unit 52 is smaller than the second reading size Z2, and the size Z of the input image data is the second reading size. If it is smaller than Z2, the control signal control unit 48 generates a continuation signal as a control signal for continuing the reading of the input image data, sends it to the image reading unit 41, and continues as a control signal for continuing the writing of the output image data. A signal is generated and sent to the image writing unit 47. Thereby, the image reading unit 41 increments the reading position of the input image data, reads the next input image data, converts the color space of the read input image data, and determines the first converted image data as a sampling condition determination Sent to the unit 42, the histogram creation unit 43, and the image correction unit 46. Further, the image writing unit 47 converts the color space of the second converted image data, increments the writing position of the output image data, and writes the output image data in the output image storage unit 53.

  When the size Z of the input image data read by the image reading unit 41 from the input image storage unit 52 becomes equal to the second read size Z2, the control signal control unit 48 uses a stop signal as a control signal for stopping reading of the input image data. Is generated and sent to the image reading unit 41, and a stop signal is generated as a control signal for stopping writing of the output image data, and is sent to the image writing unit 47.

  As a result, the image reading unit 41 stops reading the input image data, the image writing unit 47 stops recording the output image data in the output image storage unit 53, and the image output unit 54 passes through the output interface 16. The output image data is sent to the printer unit 30. Upon receiving the output image data sent from the control unit 12, the printer unit 30 extracts the image data of each color from the output image data and sends the image data of each color to the LED head.

Next, a flowchart will be described.
Step S31 The image input unit 51 acquires input image data.
Step S32: The control signal control unit 48 sends a start signal, the image reading unit 41 initializes the reading position, and the image writing unit 47 initializes the writing position.
Step S33: The parameter setting unit 45b sets a general-purpose conversion table.
Step S34: The image reading unit 41 reads the input image data and converts the color space.
Step S35: The thinning determination unit 42a determines whether the input pixel is not a thinning target pixel. If the input pixel is not a thinning target pixel, the process proceeds to step S36. If the input pixel is a thinning target pixel, the process proceeds to step S38.
Step S36: The threshold determination unit 42b determines whether or not the pixel value of the input pixel is within the effective range. If the pixel value of the input pixel falls within the valid range, the process proceeds to step S37. If the pixel value of the input pixel does not fall within the valid range, the process proceeds to step S38.
Step S37: The comprehensive judgment unit 42c sets the sampling judgment signal to 1.
Step S38: The comprehensive judgment unit 42c sets the sampling judgment signal to 0.
Step S39: The histogram creation unit 43 determines whether or not the sampling determination signal is 1. If the sampling determination signal is 1, the process proceeds to step S40. If the sampling determination signal is not 1, the process proceeds to step S43.
Step S40 The histogram creation unit 43 counts the histogram frequency G (L).
Step S41 The image correction unit 46 performs image correction processing.
Step S42: The image writing unit 47 converts the color space and writes the output image data.
Step S43: The image reading unit 41 determines whether the size Z of the input image data is smaller than the first reading size Z1. If the input image data size Z is smaller than the first read size Z1, the process proceeds to step S44. If the input image data size Z is greater than or equal to the first read size Z1, the process proceeds to step S45.
Step S44 The control signal control unit 48 sends a continuation signal, the image reading unit 41 increments the reading position, the image writing unit 47 increments the writing position, and the process returns to step S34.
Step S45: The control signal control unit 48 sends a stop signal.
Step S46: The parameter deriving unit 45 determines whether or not the validity determination signal is 1. If the validity determination signal is 1, the process proceeds to step S47. If the validity determination signal is not 1, the process proceeds to step S53.
Step S47: The feature amount calculation unit 45a calculates a feature amount.
Step S48: The parameter setting unit 45b sets a setting conversion table.
Step S49 The control signal control unit 48 sends a start signal, the image reading unit 41 initializes the reading position, and the image writing unit 47 initializes the writing position.
Step S50 The image reading unit 41 reads the input image data and converts the color space.
Step S51 The image correction unit 46 performs image correction processing.
Step S52 The image writing unit 47 converts the color space and writes the output image data.
Step S53: The image reading unit 41 determines whether the size Z of the input image data is smaller than the second reading size Z2. If the size Z of the input image data is smaller than the second read size Z2, the process proceeds to step S55. If the size Z of the input image data is greater than or equal to the second read size Z2, the process proceeds to step S56.
Step S55 The control signal control unit 48 sends a continuation signal, the image reading unit 41 increments the reading position, the image writing unit 47 increments the writing position, and the process returns to step S50.
Step S56: The control signal control unit 48 sends a stop signal.
Step S57 The image output unit 54 sends the output image data to the printer unit 30 and ends the process.

  Next, operations of the image reading unit 41 and the image writing unit 47 in the first and second embodiments will be described.

  FIG. 18 is a diagram showing the operations of the image reading unit and the image writing unit in the first embodiment of the present invention, and FIG. 19 is the operations of the image reading unit and the image writing unit in the second embodiment of the present invention. FIG.

  As shown in FIG. 18, in the first embodiment, the image reading unit 41 starts reading the input image data from the page start address (start) at the timing t0, and the sampling condition determining unit 42 performs the sampling condition. While the determination process and the histogram creation process by the histogram creation unit 43 are being performed, the output image data is not written by the image writing unit 47.

  At time t1, when the size Z of the input image data read from the input image storage unit 52 by the image reading unit 41 becomes equal to the first reading size Z1, reading of the input image data by the image reading unit 41 is stopped. The validity determination process by the validity determination unit 44 and the parameter setting process by the parameter derivation unit 45 are performed, and the setting end signal is output by the parameter derivation unit 45 at the timing t2, and the image reading unit 41 and the image writing unit 47 are output. Is read from the page head address of the input image data by the image reading unit 41, the correction processing by the image correction unit 46 is performed on all the input image data, and the output image by the image writing unit 47 Writing of data from the page top address is started.

  Also, as shown in FIG. 19, in the second embodiment, the image reading unit 41 starts reading the input image data from the page head address (top) at the timing t0, and the sampling condition determining unit 42 Sampling condition determination processing and histogram creation processing by the histogram creation unit 43 are performed. At this time, the image correction unit 46 uses the general-purpose conversion table to perform image correction processing by parallel processing, and by the image writing unit 47. Writing of the output image data from the page head address (head) is started.

  At time t1, when the size Z of the input image data read from the input image storage unit 52 by the image reading unit 41 becomes equal to the first reading size Z1, the input image data is read by the image reading unit 41 and the image document is read. Writing of the output image data by the insertion unit 47 is stopped.

  Subsequently, the validity determination process is performed by the validity determination unit 44. When the validity determination signal is output as 0 (invalid) by the validity determination unit 44, the control signal control unit 48 outputs the signal at timing t2. A restart signal is generated as a control signal and sent to the image reading unit 41 and the image writing unit 47. The image reading unit 41 resumes reading of input image data, and the image writing unit 47 resumes writing of output image data.

  Thereafter, until the size Z of the input image data read from the input image storage unit 52 by the image reading unit 41 becomes equal to the second reading size Z2, the input image data is read by the image reading unit 41, and the image correction unit 46 Image correction processing using the general-purpose conversion table, and output image data writing by the image writing unit 47 are performed.

  In this case, since the validity determination signal is 0 (invalid) and the general-purpose conversion table is continuously used, the image data that has already undergone the image correction process is valid, and the image correction process is started at timing t2. There is no need to do. Therefore, the processing time by the image reading unit 41 and the image writing unit 47 can be shortened.

  Thus, in the present embodiment, when the validity determination unit 44 determines that the histogram is not valid, a restart signal is generated as a control signal, and the restart signal is used as the image reading unit 41 and the image writing unit 47. Since the input image data is read by the image reading unit 41, the correction processing based on the general-purpose conversion table by the image correcting unit 46, and the output image data is written by the image writing unit 47, the image reading unit 41 is continued. In addition, the processing time by the image writing unit 47 can be shortened.

  In each of the above embodiments, a histogram is created based on the lightness value L. However, a histogram can be created based on the element of the pixel value.

  In each of the above embodiments, the image reading unit 41 inputs the background area in the original image in which characters, graphics, and the like are not formed, among the input image data recorded in the input image storage unit 52. The image data is read, and the histogram creation unit 43 creates a histogram based on the pixel value of the input pixel of the first converted image data corresponding to the input image data of the background area where no image is formed. However, the image reading unit 41 can create a histogram based on the pixel values of the input pixels of the first converted image data corresponding to all the input image data.

  In this case, in the created histogram, in addition to the frequency distribution formed by the color components of the background area, a plurality of frequencies are formed by images such as characters and figures, but are formed by the color components of the background area. Since the frequency distribution has the highest lightness value L, the validity determination unit 44 determines whether the histogram is valid based on the frequency distribution with the highest lightness value L, and the parameter derivation unit 45 determines the lightness value. Setting parameters are set based on the frequency distribution with the highest L.

  Further, in each of the above-described embodiments, the color multifunction peripheral 10 has been described. However, the present invention may be applied to a monochrome multifunction peripheral or an image processing apparatus such as a copying machine or a facsimile. Can do.

  The present invention is not limited to the above embodiments, and various modifications can be made based on the gist of the present invention, and they are not excluded from the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Multifunction device 30 Printer part 41 Image reading part 43 Histogram preparation part 44 Effectiveness determination part 45 Parameter derivation part 46 Image correction part 47 Image writing part 51 Image input part 52 Input image storage part 53 Output image storage part 54 Image output part

Claims (10)

(A) a first image storage unit for recording input image data acquired by the image input unit;
(B) an image reading unit that reads the input image data from the first image storage unit, converts a color space, and generates first converted image data;
(C) a histogram creating unit that creates a histogram based on the first converted image data;
(D) an effectiveness determination unit that determines whether or not the histogram created by the histogram creation unit is valid;
(E) a parameter derivation unit that sets parameters for correcting input image data when the histogram is valid;
(F) an image correcting unit that corrects the first converted image data and generates second converted image data based on the parameters set by the parameter deriving unit;
(G) an image writing unit that reads the second converted image data, converts a color space to generate output image data, and records the output image data in a second image storage unit;
(H) An image processing apparatus comprising: an image output unit that reads out output image data recorded in the second image storage unit and sends the output image data to an output device.   The effectiveness determination unit determines whether the total value of the frequencies of the histogram created by the histogram creation unit is equal to or greater than a threshold value, and determines that the histogram is valid when the total value is equal to or greater than the threshold value. Item 8. The image processing apparatus according to Item 1. (A) a sampling condition determining unit that determines whether or not an input pixel of the input image data satisfies a sampling condition;
(B) The image processing apparatus according to claim 1, wherein when the input pixel satisfies a sampling condition, the histogram creation unit creates a histogram based on the input pixel determined to satisfy the sampling condition.   The image processing apparatus according to claim 3, wherein the sampling condition determining unit determines that the input pixel satisfies the sampling condition when the input pixel is not a thinning target pixel.   The image processing apparatus according to claim 3, wherein the sampling condition determination unit determines that the input pixel satisfies the sampling condition when a pixel value of the input pixel is within an effective range.   As the parameter is set by the parameter deriving unit, the image reading unit starts reading the input image data again from the top of the first image storage unit, and the image writing unit The image processing apparatus according to claim 1, wherein writing of output image data is started from the head of the image storage unit.   The parameter derivation unit sets a setting conversion table as a parameter when the validity determination unit determines that the histogram is valid, and as a parameter when the validity determination unit determines that the histogram is not valid. The image processing apparatus according to claim 6, wherein a general-purpose conversion table is set. (A) The parameter derivation unit sets a general-purpose conversion table as an initial parameter,
(B) Creation of a histogram by the histogram creation unit, correction of first converted image data based on a general-purpose conversion table by the image correction unit, and writing of output image data by the image writing unit are performed in parallel. The image processing apparatus according to any one of claims 1 to 5. (A) having a control signal control unit that generates a control signal based on the determination result of the effectiveness of the histogram by the effectiveness determination unit;
(B) Based on the control signal generated by the control signal control unit, the image reading unit reads input image data from the first image storage unit, and the image writing unit is a second image storage unit. The image processing apparatus according to claim 8, wherein the output image data is written in the.   The control signal control unit generates a start signal as a control signal when the validity determination unit determines that the histogram is valid, sends the start signal to the image reading unit and the image writing unit, and The image processing apparatus according to claim 9, wherein when the determination unit determines that the histogram is not valid, a restart signal is generated as a control signal, and the restart signal is sent to the image reading unit and the image writing unit.

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