JP2010118769A - Image processor, image reader, image formation device, image processing method, computer program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processor capable of improving a processing speed to reduce a used amount of a memory for storing a document image therein when the tilt of a document is at a level requiring no correction, and to provide an image reader, an image formation device, an image processing method, a computer program and a recording medium with the computer program recorded therein. <P>SOLUTION: A document detection part 24 includes a tilt detection part 241 for detecting presence of the tilt of a document from digital signals (document image) of RGB. A document correction part 25 includes a tilt angle calculation part 251 for calculating the angle of the tilt of the document from the document image, and a correction part 252 for correcting the tilt of the document by rotating the document image by only an angle portion calculated by the tilt angle calculation part 251 when the tilt detection part 241 detects the presence of tilt. When the tilt detection part 241 detects presence (or absence) of tilt, an output selection part 253 outputs a document image output by the correction part 252 (or a memory 242) with the tilt corrected (or without correcting the tilt) to a subsequent stage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image processing method for calculating an amount of document inclination from an acquired document image, an image processing apparatus, an image reading apparatus and an image forming apparatus provided with the image processing apparatus, and a computer for realizing the image processing apparatus. The present invention relates to a program and a recording medium on which the computer program is recorded.

  When an original image processed by a copier, multifunction device, scanner, or the like is created as image data, image processing such as correction of the inclination of the original, image shaping, and noise removal is often performed when the original is read. . Among these image processes, correction of document inclination is positioned as a particularly important process, and various processing methods and processing apparatuses have already been realized.

  FIG. 10 is an explanatory diagram showing a state where image processing is performed on a document image to correct the inclination of the document. For example, in Japanese Patent Application Laid-Open No. 2004-133260, the inclination angle of a document is calculated from the vertex of the document detected from the document image, and the document image is rotated by the calculated angle to correct the document inclination.

Further, in Patent Document 1, when a document placed on a document table is read as image data, the inclination angle of the document from the read image data is set only when the correction of the document tilt is set in advance. A technique for correcting image data by calculating the above is disclosed. As a result, when it is set in advance that correction of the inclination of the document is unnecessary, the inclination of the document is not calculated and the inclination is not corrected, so that image processing is performed at high speed.
JP-A-11-331547

  However, in the technique disclosed in Patent Document 1, when it is set in advance that correction of the inclination of the document is necessary, the inclination angle is calculated even when the inclination of the document does not require correction. Since the tilt correction is performed, the processing speed of the image processing is reduced, and there is a problem that a predetermined amount of memory for storing the document image is always required. This problem is common to both the case where the document placed on the platen is read and image processing is performed, and the case where the document conveyed by the document conveying means is read and image processing is performed.

  The present invention has been made in view of such circumstances, and the object of the present invention is to detect the inclination of the document step by step so that the inclination of the document does not require correction. Image processing apparatus, image reading apparatus, image forming apparatus, image processing method, and computer program for realizing the image processing apparatus capable of improving processing speed and reducing the amount of memory used to store a document image And providing a recording medium on which the computer program is recorded.

  An image processing apparatus according to the present invention includes means for acquiring an original image read by scanning an original, and calculation means for calculating an amount of inclination of the original with respect to the scanning direction from the original image acquired by the means. The image processing apparatus includes a detecting unit that detects whether or not the document is tilted from the document image. When the detecting unit detects no tilt, the calculating unit does not calculate the amount of tilt of the document. It is characterized by being.

  The image processing apparatus according to the present invention includes means for correcting the inclination of the original of the original image based on the amount of inclination calculated by the calculating means.

  An image reading apparatus according to the present invention includes means for scanning and reading an image formed on a document, and the image processing apparatus according to any one of the above-described inventions for acquiring a document image read by the means. It is characterized by that.

  An image forming apparatus according to the present invention includes the image processing apparatus according to any one of the above-described inventions, and an image forming unit that forms an output image based on a document image processed by the image processing apparatus. It is characterized by.

  The image processing method according to the present invention is an image processing method for acquiring a document image read by scanning a document, and calculating an inclination amount of the document with respect to the scanning direction from the acquired document image in a calculation step. The method includes a step of detecting whether or not the document is tilted from the document image, and when no tilt is detected in the step, the calculation step does not calculate the amount of tilt of the document.

  The image processing method according to the present invention includes a step of correcting the inclination of the original of the original image based on the amount of inclination calculated in the calculating step.

  A computer program according to the present invention is a computer program that causes a computer that acquires image data and performs image processing to calculate an amount of inclination of an original with respect to the scanning direction from an original image scanned and read in a calculation step. A step of causing a computer to extract a predetermined index of the document from the document image, and a step of detecting whether or not the document is tilted based on a deviation of the index extracted in the step with respect to the scanning direction. When no inclination is detected in step 1, the amount of document inclination is not calculated in the calculation step.

  The computer program according to the present invention includes a step of causing the computer to correct the inclination of the original of the original image based on the amount of inclination calculated in the calculating step.

  A recording medium according to the present invention records the computer program according to any one of the above-described inventions.

In the present invention, calculation of the amount of inclination of the document and detection of the presence / absence of the inclination are performed in parallel, and when no inclination of the document is detected from a part of the document image, the amount of inclination of the document is calculated. Do not do.
As a result, when no inclination of the original is first detected from a part of the original image, the image processing is faster than when the amount of inclination is calculated from the entire original image, and a part of the original image is stored in the memory. Just remember. Also, for example, when document images of a plurality of documents fed continuously from a document feeder are acquired and image processing is performed, image processing is significantly speeded up because the rate of document tilt is small. .

  In the present invention, since the inclination of the original of the original image is corrected based on the calculated amount of inclination, when it is detected that the original is inclined, the inclination of the original is determined based on the amount of inclination calculated with high accuracy. Correct.

In the present invention, image processing is performed on the document image obtained by scanning and reading the image formed on the document by the image processing apparatus according to the above-described invention.
This speeds up the overall image reading process.

In the present invention, an output image is formed based on a document image processed by the image processing apparatus according to the above-described invention.
As a result, the image processing apparatus with high-speed image processing is applied to a printer device, a digital multi-function peripheral, and the like.

  In the present invention, each unit of the image processing apparatus described above is realized by a computer program read from a recording medium.

According to the present invention, calculation of the amount of inclination of the document and detection of the presence or absence of inclination are performed in parallel.
As a result, when it is first detected that there is no document skew from a part of the document image, the image processing is faster than when the amount of tilt is calculated from the entire document image. Therefore, the processing speed can be improved when the inclination of the document is such that no correction is required.

The image processing apparatus and the image forming apparatus according to the present invention will be described below as a digital color multifunction peripheral having functions such as a copier, printer, facsimile, scan to e-mail, and the image processing apparatus according to the present invention as a color image reading apparatus. Embodiments applied respectively to will be described in detail.
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a digital color multifunction peripheral 100 according to Embodiment 1 of the present invention. In the figure, reference numeral 100 denotes a digital color multifunction peripheral. The digital color multifunction peripheral 100 has a CCD (Charge Coupled Device) line sensor, and RGB (R: red, G) obtained by reading reflected light from a document. : Green, B: blue) image input device 5 that outputs an analog signal as an original image, and CMYK (C: cyan, M: magenta, Y: yellow, K: black) digital color obtained by acquiring the analog signal. An image processing apparatus 2 that outputs a signal is provided.

  The digital color multifunction peripheral 100 also includes an image output device 3 that forms an output image on a recording sheet by an output method such as a photographic method or an ink jet method based on a digital color signal given from the image processing device 2, and an LCD (Liquid An operation panel 6 is provided which includes a crystal display) and various keys and receives operations on the above-described devices.

  The image processing device 2 includes an A / D conversion unit 20 that converts an analog document image input from the image input device 5 into a digital document image, and an RGB digital signal output from the A / D conversion unit 20. The image input apparatus 5 includes a shading correction unit 21 that removes various distortions generated in the illumination system, the imaging system, and the imaging system, and an input processing unit 22 that performs gradation correction (hereinafter referred to as gamma correction). The RGB digital signal (original image) output from the input processing unit 22 is temporarily stored / read out to / from a transmission / reception unit / storage unit 23 having a large-capacity storage device such as a hard disk, and the original detection unit 24 is used. The inclination of the document image is corrected by being supplied to the document correction unit 25.

  The image processing apparatus 2 also converts the RGB digital signal output from the document correction unit 25 into a CMY signal corresponding to RGB complementary colors and performs a process for improving color reproducibility, and a color correction unit 27. Is provided with a black generation / undercolor removal unit 28 that generates a CMYK digital color signal based on the CMY signal output from the. The CMYK digital color signal output from the black generation / undercolor removal unit 28 is subjected to enhancement processing and smoothing processing in the spatial filter unit 29 and then to a halftone generation unit 30 in which gradation reproduction processing is performed. This is given to the image output device 3.

The RGB digital signals output from the document correction unit 25 are also supplied to the region separation unit 31. The area separation unit 31 is an area identification signal that indicates which area each pixel included in the digital signal belongs to among areas such as black characters, color characters, halftone dots, and photographic paper photographs (continuous tone areas). And is supplied to the black generation / undercolor removal unit 28, the spatial filter unit 29, and the halftone generation unit 30.
Each unit of the image processing apparatus 2 described above is connected to a control unit 40 including a CPU 401, a ROM 402 that stores information such as a program, and a RAM 403 that stores temporarily generated information. The operation of each unit is controlled according to a control program stored in the ROM 402 in advance. The control unit 40 may be configured by an application specific integrated circuit (ASIC) or a digital signal processor (DSP).

  The RGB digital signal output from the document correction unit 25 is supplied to the color correction unit 27 and the region separation unit 31 as described above, and is also converted into the PDF format, and a network interface and a communication line interface (both not shown). To the external connection device and the communication line, respectively. The digital signal may also be compressed into a JPEG code based on a JPEG compression algorithm, stored in the transmission / reception unit / storage unit 23 as filing data, and managed.

When copy output and print output are instructed for the stored data, the target JPEG code is read from the large-capacity storage device of the transmission / reception unit / storage unit 23 and is given to a JPEG decompression unit (not shown) to be combined. And converted into the original RGB digital signal.
On the other hand, when an image transmission is instructed, the target JPEG code is read from the mass storage device of the transmission / reception unit / storage unit 23 and transmitted to the external connection device and the communication line via the network interface and the communication line interface, respectively. Is done.

  FIG. 2 is a schematic front sectional view showing the configuration of the image input device 5. The image input device 5 includes a document conveying unit 51 configured in an upper casing and a scanner unit 56 configured in a lower casing.

  The document transport unit 51 includes a document set sensor 514 that detects a document placed face down on a document tray 511 that is inclined from one side to the other. Above the lower end portion of the document tray 511, an attracting roller 512 is disposed for bringing the documents detected by the document setting sensor 514 one by one downstream. A conveyance path S formed by a guide is provided on the downstream side of the document tray 511, and a document is placed on the upper end and the middle of the conveyance path S up to a reading position R at the other end of the document table 561 described later. Conveying rollers 513a and 513b for conveying are respectively provided. On the other side of the reading position R, a document discharge roller 50 that discharges the read document and a document discharge sensor 567 that detects the discharged document are arranged.

  The conveyance roller (alignment roller) 513b has an electromagnetic clutch (not shown) on the drive shaft, and the transmission of rotational driving force by a drive motor (not shown) is controlled. When the document is not placed on the document tray 511, the drive shaft of the transport roller 513b is restrained and stopped by the electromagnetic clutch.

  A document is placed on the document tray 511, and the leading edge of the document conveyed downstream contacts a feeding timing sensor 515 disposed between the conveyance roller 513a and the conveyance roller 513b. When the signal is issued, the excitation state of the electromagnet built in the electromagnetic clutch is switched at a predetermined timing. As a result, the transport roller 513b releases the restraint of the drive shaft and starts to rotate in the direction of transporting the document downstream. At this time, the leading end portion of the document conveyed from the upstream side has already reached the nip portion of the conveying roller 513b, and the nip portion of the conveying roller 513b is formed so that the leading end portion of the document is formed after a predetermined deflection is formed on the document. It operates so as to be transported to the downstream side with being aligned so as to be substantially perpendicular to the transport direction.

  The scanner unit 56 includes scanning units 562 and 563 that translate in parallel to both sides while reading a document along the lower surface of the mounting table 561 for placing the document horizontally. On one side of the scanning unit 563, an imaging lens 564 is provided for converging the light read by the scanning unit 562. The light converged by the imaging lens 564 is a CCD line sensor. An image is formed on 565. On the other side of the scanner unit 56, a tray 566 is provided so as to project the document transported from the transport path S described above, read at the reading position R and discharged, face-down.

  The scanning unit 562 includes a light source 562a composed of, for example, a halogen lamp for irradiating light on the original conveyed from the original tray 511 and the original placed on the original table 561, and reflects light reflected from the original in the mirror 562a. Is reflected to the other side. The scanning unit 563 includes mirrors 563a and 563b that reflect light reflected by the mirror 562a of the scanning unit 562 downward and to one side, respectively, and the light reflected by the mirror 563b passes through the imaging lens 564 to the CCD line. An image is formed on the sensor 565 as a document image. The CCD line sensor 565 photoelectrically converts the formed original image to generate RGB analog signals.

  The image input device 5 configured as described above can be operated in two types of modes: a stationary reading mode in which a document is read while being read, and a traveling reading mode in which the document is read while being conveyed. In the stationary reading mode, when the document is placed on the document table 561, for example, when a start key (not shown) on the operation panel 6 is pressed, the scanning units 562 and 563 are scanned to the other side to reflect the reflected light from the document. It is a reading mode. In the travel reading mode, when a document is placed on the document tray 511 and the document set sensor 514 detects the document, the document is brought in when the start key is pressed, and the feeding roller 512 and the transport rollers 513a and 513b. In this mode, the reflected light from the document at the reading position R is read one sheet at a time.

  FIG. 3 is a block diagram showing functional configurations of the document detection unit 24 and the document correction unit 25. The document detection unit 24 includes an inclination detection unit 241 that detects the presence or absence of the document from the RGB digital signal (document image) given from the input processing unit 22, and a memory 242 that stores the document image for one page. In addition, the document correction unit 25 stores the memory when the tilt angle calculation unit 251 that calculates the tilt angle of the document from the document image supplied via the document detection unit 24 and the tilt detection unit 241 detect the presence of tilt. A correction unit 252 that corrects the inclination of the original by rotating the original image supplied from 242 by the angle calculated by the inclination angle calculation unit 251, and selectively selects the original image supplied from the correction unit 252 and the memory 242. And an output selection unit 253 that outputs to the subsequent stage as RGB digital signals (original images).

The inclination detection unit 241 detects the document edge (edge) for each line corresponding to the scanning line in the main scanning direction when a given document image is scanned, and determines the number of pixels existing between the left and right document edges. The presence or absence of inclination is detected based on the deviation between the lines, and the detection result is given to the inclination angle calculation unit 251, the correction unit 252 and the output selection unit 253. The inclination detection unit 241 also supplies an original pixel signal indicating a period during which the original pixels of each line are supplied to the original detection unit 24 to the inclination angle calculation unit 251.
The memory 242 reads and outputs one page of document images at timings required by the correction unit 252 and the output selection unit 253, respectively.

The inclination angle calculation unit 251 starts calculation at the same time when the inclination detection unit 241 starts detection, and stops calculation when the inclination detection unit 241 detects no inclination.
The output selection unit 253, when the tilt detection unit 241 detects that there is a tilt (or no), the document image with the tilt corrected (or not corrected) output from the correction unit 252 (or the memory 242) to the subsequent stage. Output. In this case, the output selection unit 253 may start output after the correction unit 252 finishes correcting the inclination (or after the inclination detection unit 241 detects no inclination).

The correction unit 252 corrects the inclination of the original of the original image by affine transformation expressed by the following equation (1). In the affine transformation, when a cosine (cos θ) and a sine (sin θ) with respect to an inclination angle (θ) are given, the coordinates (x, y) can be converted into coordinates (x ′, y ′).
In equation (1), the coordinates of one vertex of the document are (x0, y0), and the vertex becomes the origin after conversion.

  FIG. 4 is an explanatory diagram showing a method for calculating the cosine and sine with respect to the angle of inclination of the document. In the figure, the horizontal axis represents the distance (x) separated from the origin (0, 0) of the coordinates in the document image in the main scanning direction, and the vertical axis represents the origin (0, 0) in the sub-scanning direction orthogonal to the main scanning direction. Represents the distance away from.

  First, the distance from the origin (0, 0) is calculated for each of the four vertices of the document, and the coordinates of the vertex closest to the origin (0, 0) are determined from P0 (x0, y0) and the origin (0, 0). Let the other two vertices except the farthest vertex be P1 (x1, y1) and P2 (x2, y2), respectively. In addition, the angles formed by the x-axis and the line segment P0P1 and the y-axis and the line segment P0P2 are θ1 and θ2, respectively. At this time, the respective cosine and sine for θ1 and θ2 can be obtained by the following equations (2) to (5).

  Next, an angle to be corrected for tilt is selected from the two angles θ1 and θ2. Here, the smaller angle is selected. That is, the magnitudes of cos θ1 and cos θ2 are compared, and it is determined that the angle corresponding to the larger cosine (θ1 or θ2) is an angle to be corrected for inclination.

FIG. 5 is a flowchart of a main routine showing a processing procedure of the CPU 401 for detecting whether or not the document is tilted in the tilt detecting unit 241. The following processing is executed each time acquisition of one page of a document image is started in accordance with a control program stored in the ROM 402 in advance. In this process, the deviation of the document width with respect to the previous line is calculated for each line of the document image given from the input processing unit 22, and when the deviation is larger than a predetermined threshold, the presence of document inclination is detected.
Note that the processing executed by the CPU 401 may be executed by dedicated hardware such as the above-described ASIC, a DSP, or a combination thereof.

The detection of the presence / absence of tilt is not limited to this process, and any process that can process at a higher speed than the detection of the tilt angle of the document using a part of the document image may be used.
The “increment threshold value”, “number of determination lines”, and “final line” are set in advance in the RAM 403 based on the resolution when the document is read by the image input device 5, respectively. “Line counter”, “Number of effective lines”, “Previous line document width”, “Tilt flag”, and “Document width” are variables stored in the RAM 403, respectively.

  When starting processing for one page of the document image, the CPU 401 performs initialization processing (step S11), sets “0” in the “line counter” indicating the number of the line being processed, and the number of lines on which the document exists. “0” is stored in the “number of effective lines” indicating “1”, “0” is stored in the “prior line original width” that stores the original width of the previous line, and “inclination” indicates that the original of the original image to be detected is inclined. Write “1” to “Flag”. Then, the CPU 401 calls and executes a subroutine related to document width calculation (step S12).

Thereafter, the CPU 401 determines whether or not the “number of effective lines” is equal to or greater than the “number of determination lines” (step S13). The “number of determination lines” here is preferably about 2 to 30 when the resolution when the image input apparatus 5 reads a document is 600 dpi, for example.
If it is determined that the “number of effective lines” is equal to or greater than the “number of determination lines” (step S13: YES), the CPU 401 ends the process without determining the calculated document width. If it is determined that it is not equal to or greater than the “number of determination lines” (step S13: NO), the CPU 401 determines whether or not the calculated “document width” is “0” (step S14).

  If it is determined that “document width” is “0” (step S14: YES), the CPU 401 proceeds to step S20 assuming that no document exists on the line being processed. If it is determined that the “document width” is not “0” (step S14: NO), the CPU 401 adds “1” to the “number of effective lines” on the assumption that the document exists on the line being processed (step S15). ). Thereafter, the CPU 401 calculates the increment of the document width by subtracting the “front line document width” from the “document width” (step S16). Then, the CPU 401 writes and updates the “original width” in the “previous line original width” for processing for the next line (step S17).

Next, the CPU 401 determines whether or not the calculated increment of the document width is larger than the “increment threshold” (step S18). For example, when the resolution when the image input apparatus 5 reads a document is 600 dpi (dot per inch) and the minimum angle for determining that there is an inclination is 0.1 degree, the “increment threshold” here is from 580 A value of about 600 is preferred.
If it is determined that the increment is not greater than the “increment threshold” (step S18: NO), the CPU 401 advances the process to step S20.

  When it is determined that the increment is larger than the “increment threshold” (step S18: YES), that is, when the deviation of the document width increases rapidly between adjacent lines, the CPU 401 detects that there is no inclination. To indicate this, “0” is written in the “tilt flag” (step S19). Thereafter, the CPU 401 adds “1” to the “line counter” in order to process the next line (step S20). Then, the CPU 401 determines whether or not the “line counter” is larger than the “final line” (step S21).

  If it is determined that the “line counter” is not greater than the “final line” (step S21: NO), the CPU 401 returns the process to step S12 in order to calculate the document width for the next line. When it is determined that the “line counter” is larger than the “final line” (step S21: YES), the CPU 401 writes “0” in the “tilt flag” to indicate that no tilt is detected (step S22). The process is terminated.

  The “tilt flag” set by the above processing is the detection result of the presence or absence of tilt (with tilt = “1”), which is executed by the CPU 401 in the tilt angle calculation unit 251, correction unit 252, and output selection unit 253 described above. It is referred in the process to do.

FIG. 6 is a flowchart illustrating an example of a processing procedure of the CPU 401 related to a document width calculation subroutine. In this subroutine, the left end and the right end of the original are detected for each line of the original image given from the input processing unit 22, and the number of pixels existing from the left end to the right end is written in the “original width”. Further, the above-described document image signal is turned on only during a period in which pixels from the left end to the right end are given.
The “coordinate counter”, “left end coordinate”, and “right end coordinate” are variables stored in the RAM 403, respectively. The “line end” is set in advance in the RAM 403 based on the resolution when the document is read by the image input device 5.

  When called from the main routine, the CPU 401 performs initialization processing (step S31), sets “0” in the “coordinate counter” indicating the position of the pixel being processed in the line being processed, Write “0” in “Left end coordinates” and “Right end coordinates” that store the coordinates of the right end, respectively. Thereafter, the CPU 401 adds “1” to the “coordinate counter” in order to process the next pixel on the same line (step S32), and whether or not the “coordinate counter” is greater than the “line end”. Is determined (step S33). When it determines with having become large (step S33: YES), CPU401 advances a process to step S43.

If it is determined that the “coordinate counter” is not greater than the “line end” (step S33: NO), the CPU 401 performs a process of detecting the left end of the document (step S34). The left end detection process here is performed as shown in the following (a) to (d).
(A) The pixel density when there is no document is registered in the RAM 403 in advance as a reference density value.
(B) The density of each pixel of a given document image is compared with the reference density value to classify pixels where the document exists and pixels where the document does not exist.
(C) In order to prevent erroneous determination due to document reading noise, density smoothing filter processing is performed with reference to eight neighboring pixels adjacent to the pixel being processed.
(D) The pixel coordinates when the pixel where the document does not exist is changed to the pixel where the document exists are defined as the left end of the document.

  Next, the CPU 401 determines whether or not the left edge of the document has been detected (step S35). If it is determined that it has not been detected (step S35: NO), the process returns to step S32. If it is determined that the left end has been detected (step S35: YES), the CPU 401 writes the “coordinate counter” being processed into the “left end coordinate” (step S36) and turns on the original pixel signal (step S37). Thereafter, the CPU 401 adds “1” to the “coordinate counter” in order to process the next pixel on the same line (step S38), and whether or not the “coordinate counter” is larger than the “line end”. Is determined (step S39).

If it is determined that the “coordinate counter” has become larger than the “line end” (step S39: YES), the CPU 401 advances the process to step S43. When it is determined that it is not larger than the “line end” (step S39: NO), the CPU 401 performs a process of detecting the right end of the document (step S40). The detection process here is performed in the same manner as (a) to (d) described above. However, the coordinate of the pixel when the pixel where the document exists changes to the pixel where the document does not exist is the right end of the document.
Then, the CPU 401 determines whether or not the right edge of the document has been detected (step S41). If it is determined that it has not been detected (step S41: NO), the process returns to step S38.

  If it is determined that the right edge of the document has been detected (step S41: YES), the CPU 401 writes the “coordinate counter” being processed into the “right edge coordinates” (step S42), and further, from the “right edge coordinates” to the “left edge coordinates”. A value obtained by subtracting is written in the “document width” (step S43). If the “document width” is a negative number, that is, if the “right edge coordinate” remains “0” because the right edge is not detected, the “document width” is adjusted to “0” ( Step S44). Thereafter, the CPU 401 turns off the original pixel signal (step S45) and returns to the main routine.

  FIG. 7 is a flowchart of a main routine showing an example of a processing procedure of the CPU 401 for detecting the apex of the document in the inclination angle calculation unit 251. The following processing is executed each time acquisition of one page of a document image is started in accordance with a control program stored in the ROM 402 in advance. This process is executed in parallel with the process of detecting whether or not the document is tilted in the tilt detecting unit 241. The detected vertex is used to calculate the cosine and sine with respect to the angle of inclination of the original as shown in FIG. 4, and the inclination of the original image is corrected by equation (1) based on the calculated cosine and sine. Is done.

  “Pixel x coordinate”, “pixel y coordinate”, “upper end x coordinate”, “upper end y coordinate”, “lower end x coordinate”, “lower end y coordinate”, “left end x coordinate”, “left end y coordinate”, “Right end x coordinate” and “Right end y coordinate” are variables for storing the x coordinate and the y coordinate of the pixel being processed and the top, bottom, left, and right vertices of the document, and are stored in the RAM 403 respectively. And

  When the CPU 401 starts processing for one page of the document image, the CPU 401 performs an initialization process (step S51), and except for the “upper end y coordinate” and the “left end x coordinate”, the variables of the respective x coordinates and y coordinates described above. “0” is written to. For “upper end y coordinate” and “left end x coordinate”, in order to detect these minimum values, values that cannot normally be taken are substituted as initial values. In the first embodiment, 65535 (64k-1) and 8191 (8k-1) are substituted, respectively, but the present invention is not limited to this.

  Thereafter, the CPU 401 determines whether or not the document pixel signal indicating the period during which the document pixels of each line are given to the document detection unit 24 is turned on (step S52). This document pixel signal is a signal that is turned on / off every time the subroutine related to document width calculation shown in FIG. 6 is called from the main routine shown in FIG.

When it is determined that the document pixel signal is turned on (step S52: YES), the CPU 401 determines that the pixel being processed is included in the document, the upper end determination (step S53), the lower end determination (step S54), and the left end. Subroutines relating to determination (step S55) and right end determination (step S56) are sequentially called and executed. By executing these subroutines, the x-coordinate and y-coordinate of the upper end, lower end, left end, and right end of the document are updated.
These subroutines may be executed in any order.

  When the process of step S56 is completed, and when it is determined in step S52 that the document pixel signal is not turned on (step S52: NO), the CPU 401 sets “1” as the “tilt flag” indicating whether or not the document is tilted. It is determined whether or not (step S57). When it is determined that the “tilt flag” is not “1” (step S57: NO), that is, when it is detected that the document is not tilted, the CPU 401 immediately ends the process. Thereby, the inclination angle of the document is not calculated for the page being processed.

  When it is determined that the “tilt flag” is “1” (step S57: YES), that is, when the document has not been detected to be tilted, the CPU 401 adds “1” to the “pixel x coordinate” (step S57). S58), it is determined whether or not the “pixel x coordinate” is larger than the “line end” (step S59). If it is determined that it is not larger than the “line end” (step S59: NO), the CPU 401 returns the process to step S52 in order to set the next pixel on the same line as the processing target.

  When it is determined that “pixel x coordinate” is larger than “line end” (step S59: YES), the CPU 401 writes “0” to “pixel x coordinate” to return the x coordinate to the beginning of the line and “pixel”. “1” is added to “y-coordinate” (step S61), and the process proceeds to the next line. Thereafter, the CPU 401 determines whether or not the “pixel y coordinate” is larger than the “final line” (step S62).

  If it is determined that the “pixel y coordinate” is not larger than the “final line” (step S62: NO), the CPU 401 returns the process to step S52 in order to set the next line as a processing target. If it is determined that it is larger than the “last line” (step S62: YES), the CPU 401 ends the process assuming that the detection of the vertex of the document is completed.

  FIG. 8 is a flowchart showing the processing procedure of the CPU 401 relating to the upper end determination, lower end determination, left end determination, and right end determination subroutines. When the subroutine related to the upper end determination is called, the CPU 401 determines whether or not the “pixel y coordinate” being processed is smaller than the “upper end y coordinate” (step S71). If it is determined that it is not smaller than the “upper end y coordinate” (step S71: NO), the CPU 401 ends the process and returns to the main routine.

When it is determined that the value is smaller than the “upper end y coordinate” (step S71: YES), the CPU 401 writes the “pixel x coordinate” being processed into the “upper end x coordinate” (step S72) and the “pixel y coordinate being processed”. ”Is written in the“ upper end y coordinate ”(step S73), the x coordinate and the y coordinate of the upper end of the document are updated, and the process returns to the main routine.
In this way, the minimum value of the “upper end y coordinate” is obtained.

Similarly, when the subroutine relating to the lower end determination is called, the CPU 401 determines whether or not the “pixel y coordinate” is larger than the “lower end y coordinate” (step S75). When it is determined that it is not large (step S75: NO), the CPU 401 returns to the main routine. When it is determined that the value is larger than the “lower end y coordinate” (step S75: YES), the CPU 401 writes the “pixel x coordinate” in the “lower end x coordinate” (step S76) and the “pixel y coordinate” as the “lower end y coordinate”. "(Step S77) and the process returns to the main routine.
In this way, the maximum value of the “lower end y coordinate” is obtained.

When the subroutine relating to the left end determination is called, the CPU 401 determines whether the “pixel x coordinate” is smaller than the “left end x coordinate” (step S81). If it is determined that it is not small (step S81: NO), the CPU 401 returns to the main routine. When it is determined that it is smaller than the “left end x coordinate” (step S81: YES), the CPU 401 writes the “pixel x coordinate” in the “left end x coordinate” (step S82), and the “pixel y coordinate” in the “left end y coordinate”. "(Step S83), the process returns to the main routine.
In this way, the minimum value of the “left end x coordinate” is obtained.

Furthermore, when a subroutine related to right end determination is called, the CPU 401 determines whether or not “pixel x coordinate” is larger than “right end x coordinate” (step S85). If it is determined that it is not large (step S85: NO), the CPU 401 returns to the main routine. When it is determined that the value is larger than the “right end x coordinate” (step S85: YES), the CPU 401 writes the “pixel x coordinate” in the “right end x coordinate” (step S86) and the “pixel y coordinate” as the “right end y coordinate”. "(Step S87), the process returns to the main routine.
In this way, the maximum value of the “right end x coordinate” is obtained.

As described above, according to the first embodiment, the calculation of the inclination angle of the document and the detection of the presence / absence of the tilt are performed in parallel, and there is no document inclination from the lines corresponding to the “number of effective lines”. Is detected, the inclination angle of the original is not calculated, and the inclination of the original is not corrected.
As a result, when no inclination of the original is detected from a part of the original image, the image processing is faster than when the inclination angle is calculated from the entire original image, and a part of the original image is stored in the memory. Just remember. Therefore, when the inclination of the document is such that correction is not required, the processing speed can be improved and the amount of memory used for storing the document image can be reduced.

  Further, since the inclination of the original of the original image is corrected based on the cosine and sine of the calculated inclination angle, when it is detected that the original is inclined, the inclination of the original is calculated based on the calculated inclination angle. It becomes possible to correct.

Furthermore, an output image is formed on the basis of the original image in which the inclination of the original is corrected by the image processing apparatus.
Therefore, when the inclination of the document is such that correction is not required, an image processing device that improves the processing speed and reduces the amount of memory used to store the document image is applied to a printer device, a digital multifunction device, or the like. Is possible.

(Embodiment 2)
The first embodiment is an embodiment in which the image processing apparatus 2 and the image forming apparatus according to the present invention are applied to the digital color multifunction peripheral 100, whereas the second embodiment is a color image processing apparatus 2a according to the present invention. This is a form applied to the image reading apparatus 200.
FIG. 9 is a block diagram showing a configuration of a color image reading apparatus 200 according to Embodiment 2 of the present invention. In the figure, reference numeral 200 denotes a color image reading device. The color image reading device 200 is an image input device 5 that outputs RGB analog signals as a document image, and an image processing device that acquires the analog signals and outputs RGB digital signals. 2a and an operation panel 6a for receiving operations on these devices.

  The image processing device 2a includes an A / D conversion unit 20 that converts an analog document image input from the image input device 5 into a digital document image, and an RGB digital signal output from the A / D conversion unit 20. The image input apparatus 5 includes a shading correction unit 21 that removes various distortions generated in the illumination system, the imaging system, and the imaging system, and an input processing unit 22 that performs gamma correction. The RGB digital signal (original image) output from the input processing unit 22 is stored / read out to / from a transmission / reception unit / storage unit 23 having a large-capacity storage device such as a hard disk. It is given to the document correction unit 25.

  Each unit of the image processing apparatus 2 a described above is connected to the CPU 401, the ROM 402 that stores information such as a program, and the control unit 40 that includes the RAM 403 that stores temporarily generated information. Are controlled in accordance with a control program stored in advance.

The RGB digital signals output from the document correction unit 25 are sent to an external computer, a hard disk, and a network such as an intranet or the Internet via a device interface and a network interface (not shown).
In addition, the same code | symbol is attached | subjected to the location corresponding to Embodiment 1, and the detailed description is abbreviate | omitted.

As described above, according to the second embodiment, with respect to a document image read by the image input device, the image processing device corrects the inclination of the document.
Therefore, when the inclination of the original is such that correction is not required, an image processing apparatus that improves the processing speed and reduces the amount of memory used for storing the original image can be applied to the color reading apparatus. .

  The present invention provides a computer-readable recording medium on which program code (executable program, intermediate code program, source program) for causing a computer to execute is recorded on a document in accordance with the above-described detection result of whether or not the document is tilted. It is also possible to record an image processing method for switching between calculation / non-calculation of the amount of inclination. Accordingly, it is possible to provide a portable recording medium on which a program for performing an image processing method for switching between calculation / non-calculation of the amount of document inclination according to the detection result of the presence / absence of document inclination is portable.

  The recording medium may be, for example, a program medium such as a ROM, or a program medium that can be read by inserting the recording medium into a program reading device (not shown) provided as an external storage device. In any case, the stored program code may be configured to be accessed and executed by the CPU, or the program code may be read and downloaded to the program storage area of the RAM and executed. It may be. It is assumed that this download program is stored in the main device in advance.

  The program medium is a recording medium configured to be separable from the main body, such as a magnetic tape, a tape system such as a cassette tape, a magnetic disk represented by a floppy (registered trademark) disk and a hard disk, CD-ROM / MO / MD. / Disk systems such as optical disks represented by DVD, IC cards (including memory cards), card systems such as optical cards, mask ROM, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory) The program code may be fixedly carried on a semiconductor memory medium such as a flash ROM.

  The program medium may be a medium in which the program code is fluidly supported so that the program code can be downloaded from a communication network including the Internet. When downloading the program code from the communication network in this way, the download program may be stored in the main device in advance or may be installed from another recording medium. The present invention can also be realized in the form of a computer data signal in which the program code is embedded in a carrier wave and transmitted electronically.

  The recording medium is read by, for example, a program reading device provided in a digital color multifunction peripheral and a computer system, and the above-described image processing method is executed by a CPU. The computer system includes an image input device such as a flatbed scanner, a film scanner, and a digital camera, a computer that performs various processes such as the image processing method by loading a predetermined program, and a CRT display that displays the processing results of the computer. An image display device such as a liquid crystal display, and a printer that outputs the processing results of the computer to paper or the like. Furthermore, a communication means such as a network card and a modem for connecting to a server or the like via a network is provided.

1 is a block diagram illustrating a configuration of a digital color multifunction peripheral according to a first embodiment of the present invention. It is a typical front sectional view showing the composition of an image input device. It is a block unit showing a functional configuration of a document detection unit and a document correction unit. It is explanatory drawing which shows the method of calculating a cosine and a sine with respect to the angle of inclination of a document. 7 is a flowchart of a main routine showing a processing procedure of a CPU for detecting whether or not an original is inclined in an inclination detection unit. 5 is a flowchart illustrating an example of a processing procedure of a CPU according to a document width calculation subroutine. 10 is a flowchart of a main routine showing an example of a processing procedure of a CPU that detects a vertex of a document in an inclination angle calculation unit. It is a flowchart which shows the process sequence of CPU which concerns on each subroutine of an upper end determination, a lower end determination, a left end determination, and a right end determination. It is a block diagram which shows the structure of the color image reading apparatus which concerns on Embodiment 2 of this invention. FIG. 6 is an explanatory diagram illustrating a state in which image processing is performed on a document image to correct the inclination of the document.

Explanation of symbols

100 Digital color MFP (image forming device)
200 Color Image Reading Device 2, 2a Image Processing Device 20 A / D Conversion Unit (Means for Acquiring Document Image)
24 Document detection unit 25 Document correction unit 241 Tilt detection unit (detection means)
251 Inclination angle calculation unit (calculation means)
252 Correction unit (means for correcting inclination)
3 Image output device (image forming means)
40 control unit 401 CPU
402 ROM
403 RAM
5 Image input device (means to scan and read)
6,6a Operation panel

Claims (9)

An image processing apparatus comprising: means for acquiring an original image scanned and read from an original; and calculating means for calculating an amount of inclination of the original with respect to the scanning direction from the original image acquired by the means.
Detecting means for detecting whether or not the document is tilted from the document image;
An image processing apparatus according to claim 1, wherein when the detecting means detects no inclination, the calculating means does not calculate the amount of inclination of the document.   The image processing apparatus according to claim 1, further comprising a unit that corrects a document inclination of the document image based on the amount of inclination calculated by the calculation unit. Means for scanning and reading an image formed on a document;
An image reading apparatus comprising: the image processing apparatus according to claim 1, which acquires a document image read by the unit. The image processing apparatus according to claim 1 or 2,
An image forming apparatus comprising: an image forming unit that forms an output image based on a document image processed by the image processing apparatus. In an image processing method of acquiring a document image scanned and read from a document and calculating an amount of inclination of the document with respect to the scanning direction from the acquired document image in a calculation step.
Detecting whether or not the document is tilted from the document image,
An image processing method, wherein when no tilt is detected in this step, the amount of document tilt is not calculated in the calculation step.   6. The image processing method according to claim 5, further comprising a step of correcting the inclination of the original of the original image based on the amount of inclination calculated in the calculating step. In a computer program for causing a computer that acquires image data and performs image processing to calculate an amount of inclination of an original with respect to the scanning direction from an original image scanned and read in a calculation step,
Causing the computer to extract a predetermined index of the document from the document image;
Detecting whether or not the document is tilted based on a deviation of the index extracted in the step with respect to the scanning direction,
A computer program characterized in that when no inclination is detected in this step, the amount of document inclination is not calculated in the calculation step.   8. The computer program according to claim 7, further comprising a step of causing the computer to correct the inclination of the original of the original image based on the amount of inclination calculated in the calculating step.   9. A computer-readable recording medium in which the computer program according to claim 7 or 8 is recorded.

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