JP2012070285A - Image processing method, image processing apparatus, image reading apparatus, image forming device, computer program, and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable detection of manuscript size with high accuracy even in the case where the inclination angle of a document image with respect to a regular position is small.SOLUTION: A manuscript area detection section 45 compares the inclination angle of a document image which is calculated by an angle calculation section 42 with a threshold value. If the inclination angle is equal to or greater than the threshold value, it performs first manuscript area detection processing, and if the inclination angle is less than the threshold value, performs second manuscript area detection processing. In the first manuscript area detection processing, it is determined whether each edge of the document image is an effective edge which can be regarded as the edge of the document image or noise, and the size of the manuscript is calculated based only on the effective edge. In the second manuscript area detection processing, it is determined whether each edge of the document image is an effective edge which can be regarded as the edge of the document image or noise under the condition that a manuscript area is detected in a more limited range than said first manuscript area detection processing, and the size of the manuscript is calculated based only on the effective edge.

Description

  The present invention relates to processing of image data obtained by reading an image of an original with an image reading device such as a scanner, and in particular, an image obtained by reading an image of an original placed in an inclined state on an original table. The present invention relates to an image processing method, an image processing apparatus, an image reading apparatus, an image forming apparatus, a computer program, and a recording medium that detect the inclination and original size of an original from data.

  2. Description of the Related Art Conventionally, as a technique related to an image reading apparatus such as a scanner, a document inclination (image data inclination) and a document size are obtained from image data obtained by reading an image of a document placed on a document table in an inclined state. A technique for detecting and correcting the inclination of a document (image data) is known.

  For example, in Japanese Patent Laid-Open No. 11-331547, in a configuration in which a document is transported onto a document table by a transport belt of a document transport unit, the surface of the transport belt facing the document table (the bottom surface of the transport belt) is colored orange. This is because the reflected light of the light from the exposure lamp from the conveyor belt is the same as a color having a low spectral sensitivity for a line sensor that reads an original image, that is, black. As a result, the line sensor can distinguish the background of the original, which is normally white, from the lower surface of the conveyance belt. Further, in document inclination and document size detection and document inclination correction, edges that change from black to white and edges that change from white to black are detected in the image data read by the line sensor. Next, a change in inclination between the coordinate data of each document edge is detected, a point where the inclination changes (edge change point) is obtained, and a line segment connecting the edge change points is extracted. Next, among the extracted line segments, a line segment of 45 ° or less with respect to the sub-scanning direction is selected, and the document inclination and document size detection and document inclination correction are performed.

Japanese Patent Laid-Open No. 11-331547 (published on November 30, 1999)

  However, in the conventional method, there is a possibility that a black portion may remain at the edge of the image after the inclination correction due to the influence of the surface in contact with the document. In this case, a good image (image data) ) Can not get. On the other hand, in order to avoid such problems, when the lower surface of the conveyor belt is white, the line sensor cannot correctly detect the boundary between the lower surface of the conveyor belt and the document, and the document size can be detected correctly. Can not. Specifically, when detecting the boundary between the lower surface of the conveyance belt and the original, for example, due to scanner noise in an area in contact with the original on the lower surface of the conveyance belt, the original lower surface of the conveyance belt and the original There is a possibility that a part that is not a boundary is recognized as a boundary, and the size of the document is erroneously detected. Such a problem becomes conspicuous when the inclination angle of the document image with respect to the normal position is small.

  Therefore, the present invention provides an image processing method, an image processing apparatus, an image reading apparatus, an image forming apparatus, and a computer program capable of detecting a document size with high accuracy even when the inclination angle of the document image with respect to the normal position is small. And to provide a recording medium.

  In order to solve the above problems, an image processing apparatus according to the present invention includes a document inclination / size detection unit that detects an inclination and an original size of an original image indicated by image data obtained by reading an original, and the original inclination. In the image processing apparatus that includes a document inclination / size correction unit that corrects the inclination of the document image and the document size in the image data based on the detection result of the size detection unit, the document inclination / size detection unit An edge detection processing unit that detects upper and lower and left and right edges of the image and obtains edge coordinates indicating the position of the edge; an angle calculation unit that calculates an inclination angle of the document image based on the edge coordinates; Coordinate information conversion for converting the edge coordinates into corrected edge coordinates in a state where there is no inclination of the original image based on the inclination angle of the original image And an original area detecting unit that calculates information indicating the size of the original from the corrected edge coordinates by the original area detecting process, and the original area detecting unit is configured to detect the original image calculated by the angle calculating unit. A tilt angle is compared with a threshold value, and if the tilt angle of the document image is equal to or greater than the threshold value, a first document area detection process is performed. If the tilt angle of the document image is less than the threshold value, a second document area detection is performed. In the first document area detection processing, each edge detected by the edge detection processing unit is an effective edge that can be regarded as an edge of the document image using the corrected edge coordinates, and noise. In the second document area detection process, for each edge detected by the edge detection processing unit, the information indicating the size of the document is calculated based only on the valid edge. Whether the edge is an effective edge or noise that can be regarded as an edge of the document image on the condition that the range of detecting the document region is limited as compared to the first document region detection process using the corrected edge coordinates. This is characterized in that information indicating the size of the original is calculated based on only the valid edge.

The image processing method of the present invention also includes a document inclination / size detection step for detecting a document image inclination and document size indicated by image data obtained by reading the document, and a detection in the document inclination / size detection step. In an image processing method comprising: a document inclination / size correction step for correcting a document image inclination and document size in the image data based on a result;
The document inclination / size detection step detects the upper and lower and left and right edges of the document image and obtains edge coordinates indicating the position of the edge; and the inclination angle of the document image based on the edge coordinates An angle calculating step for calculating the original image, a coordinate information converting step for converting the edge coordinates into a corrected edge coordinate in a state where there is no inclination of the original image, based on the calculated inclination angle of the original image, and an original region detection process The document area detecting step for calculating information indicating the size of the document from the corrected edge coordinates, and in the document area detecting step, the inclination angle of the document image calculated in the angle calculating step is compared with a threshold value. If the document image tilt angle is greater than or equal to a threshold value, a first document area detection process is performed. If the document image tilt angle is less than the threshold value, a second original image is detected. An area detection process is performed, and in the first document area detection process, each edge detected in the edge detection process step is an effective edge that can be regarded as an edge of the document image using the corrected edge coordinates. In the second document area detection process, for each edge detected in the edge detection processing step, the information indicating the size of the document is calculated based only on the effective edge. Whether the edge is an effective edge or noise that can be regarded as an edge of the document image on the condition that the range of detecting the document region is limited as compared to the first document region detection process using the corrected edge coordinates. This is characterized in that information indicating the size of the original is calculated based on only the valid edge.

  According to the above configuration, in the document inclination / size detection unit (document inclination / size detection step), the edge detection processing unit (edge detection processing step) detects the upper and lower and left and right edges of the document image, and the position of the edge Is obtained. Next, in the angle calculation unit (angle calculation step), the inclination angle of the document image is calculated based on the edge coordinates. Next, in the coordinate information conversion unit (coordinate information conversion step), the edge coordinates are set in a state where there is no inclination of the original image based on the inclination angle of the original image calculated by the angle calculation unit (angle calculation step). Convert to corrected edge coordinates. Next, in the document region detection unit (document region detection step), information indicating the document size is calculated from the corrected edge coordinates by document region detection processing.

  In the document area detection unit (document area detection unit process), the inclination angle of the document image calculated by the angle calculation unit (angle calculation process) is compared with a threshold value. A first document area detection process is performed, and if the inclination angle of the document image is less than a threshold value, a second document area detection process is performed.

  In the first document area detection processing, each edge detected by the edge detection processing unit (edge detection processing step) is an effective edge that can be regarded as an edge of the document image using the corrected edge coordinates, or noise. And information indicating the size of the original is calculated based only on the valid edge. On the other hand, in the second document area detection process, the corrected edge coordinates are used for each edge detected by the edge detection processing unit (edge detection process step), and the document is detected more than in the first document area detection process. Whether the edge is a valid edge that can be regarded as an edge of the document image or noise is determined under a condition that limits the area detection range, and information indicating the document size is calculated based only on the valid edge.

  As described above, the document region detection unit (document region detection unit step) does not perform document region detection processing uniformly on image data, but determines whether the document image tilt angle is greater than or less than a threshold value. The first document area detection process and the second document area detection process are switched. In this case, the second document area detection process selected when the inclination angle of the document image is less than the threshold value detects a document area for each edge of the document image more than the first document area detection process. Whether the edge is a valid edge or noise that can be regarded as an edge of the document image is determined under a condition that limits the range to be processed. Thus, even when the original is read with the original reading apparatus in a state in which the inclination angle is small with respect to the normal arrangement state, the vertical streak of the outside area of the original generated when the original is read. Thus, it is possible to detect the document size with high accuracy by avoiding erroneous detection due to noise such as the above.

  In the image forming apparatus, the document area detection unit includes a first process and a second process as the second document area detection process. In the first process, the document process is performed by the second process. Also, it is determined whether the edge is a valid edge or noise that can be regarded as an edge of the document image under the condition that the range for detecting the document area is limited, and the first process is prioritized over the second process. If the information indicating the size of the document cannot be calculated in the first process, the second process may be performed.

  According to the above configuration, the document area detection unit includes the first process and the second process as the second document area detection process selected when the inclination angle of the document image is less than the threshold value. In the first process, it is determined whether the edge is an effective edge or noise that can be regarded as an edge of the document image under a condition that limits the range in which the document area is detected, and the first process is compared to the second process. The second process is performed when information indicating the size of the document cannot be calculated in the first process.

  As a result, in the document reading apparatus, the document size can be detected with higher accuracy when the document is read in a state in which the document is placed in a state where the inclination angle is small with respect to the normal placement state.

  In the image forming apparatus, the document area detection unit includes a first process and a second process as the second document area detection process. In the second process, the document process is performed by the first process. Determining whether the edge of the document image is an effective edge or noise under the condition that the document area is widened, and performing the first process with priority over the second process, The second process may be performed when information indicating the size of the document cannot be calculated by the first process.

  According to the above configuration, the document area detection unit includes the first process and the second process as the second document area detection process selected when the inclination angle of the document image is less than the threshold value. In the second process, it is determined whether the edge is a valid edge or noise that can be regarded as an edge of the document image under the condition that the document area is wider than in the first process, and the first process is the second process. If the information indicating the size of the document cannot be calculated in the first process, the second process is performed.

  As a result, in the document reading apparatus, the document size can be detected with higher accuracy when the document is read in a state in which the document is placed in a state where the inclination angle is small with respect to the normal placement state.

  In the image forming apparatus, the document area detection unit may calculate the first document area when the information indicating the document size cannot be calculated in the first process and the second process of the second document area detection process. One document area detection process may be performed.

  According to the above configuration, the document area detection unit selects the second document area detection process when the inclination angle of the document image is less than the threshold value, and performs the first process or the second process. However, when the information indicating the size of the document cannot be calculated by the first process and the second process, the first document area detection process is performed.

  Thus, even if information indicating the size of the document cannot be calculated by the first process and the second process of the second document area detection process, the first document area detection process performs the document It is possible to calculate information indicating the size of the. As a result, it is possible to provide a function for detecting the document size with high accuracy and a function for performing it reliably.

  As described above, in the configuration of the present invention, the document area detection process is not performed uniformly on the image data, but the first document area detection process is performed depending on whether the inclination angle of the document image is greater than or less than a threshold value. The second document area detection process is switched. In this case, the second document area detection process selected when the inclination angle of the document image is less than the threshold value detects a document area for each edge of the document image more than the first document area detection process. Whether the edge is a valid edge or noise that can be regarded as an edge of the document image is determined under a condition that limits the range to be processed. Thus, even when the original is read with the original reading apparatus in a state in which the inclination angle is small with respect to the normal arrangement state, the vertical streak of the outside area of the original generated when the original is read. Thus, it is possible to detect the document size with high accuracy by avoiding erroneous detection due to noise such as the above.

  Further, since the background of the document is a white plate, it is possible to accurately detect the document size even for a document image in which it is difficult to detect the edge of the document image at the boundary between the document itself and the white plate.

1 is a block diagram illustrating a configuration of a digital color copying machine as an image forming apparatus according to an embodiment of the present invention. It is ... figure which concerns on Example 2 of this invention. FIG. 2 is a block diagram illustrating a configuration of a document inclination / size detection unit illustrated in FIG. 1. FIG. 2 is an explanatory diagram showing a special function display initial menu displayed on an LCD display unit in the operation panel of the digital color copying machine shown in FIG. 1. 3 is a flowchart showing an outline of a procedure of original inclination / size detection processing by an original inclination / size detection unit shown in FIG. FIG. 6A is an explanatory diagram showing a first coordinate information table storing upper edge coordinates, lower edge coordinates, upper correction edge coordinates, and lower correction edge coordinates detected by the edge detection processing unit shown in FIG. It is. FIG. 6B is a second coordinate information table that stores the left edge coordinates, right edge coordinates, left correction edge coordinates, and right correction edge coordinates detected by the edge detection processing unit shown in FIG. It is explanatory drawing which shows. FIG. 5 is an explanatory diagram illustrating a tangent-angle table used by the angle calculation unit illustrated in FIG. 4. FIG. 3 is an explanatory diagram illustrating an example of a paper size table in the case of a resolution of 300 dpi used when the obtained document size is converted into a standard size in the document inclination / size detection unit illustrated in FIG. 1. 4 is a flowchart illustrating an operation of document area detection processing by a document area detection unit illustrated in FIG. 3. 10A is an explanatory diagram of the process of S14 in FIG. 9, FIG. 10B is an explanatory diagram of the process of S19 in FIG. 9, and FIG. 10C is an explanatory diagram of the process of S22 in FIG. It is. 3 is a flowchart showing an outline of document skew / size correction processing in a document skew / size corrector shown in FIG. FIG. 7 is an explanatory diagram illustrating an example of calculating a rotation source coordinate value used in the document inclination / size correction process of the document inclination / size correction unit illustrated in FIG. 1. FIG. 3 is an explanatory diagram showing an initial menu displayed on the LCD display section when “original skew / size correction” is selected on the LCD display section of the digital color copying machine 1 shown in FIG. 1. It is a block diagram which shows the other example of the digital color copying machine shown in FIG. FIG. 2 is a block diagram illustrating a configuration of an image reading apparatus including the document inclination / size detection unit and the document inclination / size correction unit illustrated in FIG. 1.

[Embodiment 1]
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a digital color copying machine as an image forming apparatus according to an embodiment of the present invention. As shown in FIG. 1, a digital color copier (image forming apparatus) 1 includes a color image input device 2, a color image processing device 3, a color image output device (printing device) 4, and an image memory 5.

  The color image input device 2 is configured by a scanner unit including a device that converts optical information, such as a CCD, into an electrical signal, and outputs a reflected light image (reflectance signal) from an original as an RGB analog signal. To do.

  The color image processing apparatus 3 includes an A / D conversion unit 11, a shading correction unit 12, an input tone correction unit 13, a document inclination / size correction unit 14, a region separation processing unit 15, a color correction unit 16, and a black generation under color removal. 17, a spatial filter processing unit 18, an output tone correction unit 19, a tone reproduction processing unit 20, and a document inclination / size detection unit 21.

  The RGB analog signal of the original image read by the color image input device 2 and input to the color image processing device 3 passes through the color image processing device 3 through the A / D conversion unit 11, the shading correction unit 12, the input floor. Tone correction unit 13, document skew / size correction unit 14, area separation processing unit 15, color correction unit 16, black generation and under color removal unit 17, spatial filter processing unit 18, output gradation correction unit 19, and gradation reproduction processing unit 20 and are output to the color image output device 4 as CMYK digital color signals.

  The A / D converter 11 converts RGB analog signals into digital signals. In the shading correction unit 12, the digital RGB signal sent from the A / D conversion unit 11 is subjected to processing for removing various distortions generated in the illumination system, imaging system, and imaging system of the color image input device 2. . Further, at the same time as adjusting the color balance, a process of converting the reflectance signal into a density (pixel value) signal is performed.

  The input tone correction unit 13 performs image quality adjustment processing such as background density removal and contrast on the RGB signal from which various distortions have been removed by the shading correction unit 12.

  The document inclination / size detection unit 21 extracts the edge of the document from the RGB signal that has been subjected to the shading correction by the shading correction unit 12 and processed by the input tone correction unit 13, and the document inclination angle and the document after the inclination correction. Correction parameters relating to the size and correction processing start position are obtained. The document inclination / size detection unit 21 performs processing using the image data from the input tone correction unit 13, and the processing here is not pipeline processing.

  The document inclination / size correction unit 14 uses the correction parameters calculated by the document inclination / size detection processing unit 21 to correct the document inclination and the document with respect to the RGB data output from the input tone correction unit 13. Correct the size.

  The processes in the document inclination / size detection unit 21 and the document inclination / size correction unit 14 are performed when “document inclination / size correction” is selected in the special function of the copy mode shown in FIG. FIG. 4 is an explanatory view showing a special function display initial menu displayed on the LCD display unit 51 in the operation panel of the digital color copying machine 1.

  The region separation processing unit 15 separates each pixel in the input image into, for example, a character region, a halftone dot region, or a photographic region based on the RGB signal input from the document inclination / size correction unit 14. In addition, the region separation processing unit 15 generates a region identification signal indicating which region each pixel belongs to based on the above separation result, and generates a black generation and under color removal unit 17, a spatial filter processing unit 18, an output gradation correction. To the unit 19 and the gradation reproduction processing unit 20.

  Further, the region separation processing unit 15 outputs the input signal as it is to the subsequent color correction unit 15. When the document inclination / size detection unit 21 and the document inclination / size correction unit 14 do not perform the processing operation, the input signal is an output signal from the input gradation correction unit 13. On the other hand, when the document inclination / size detection unit 21 and the document inclination / size correction unit 14 perform processing operations, the input signal is processed by the document inclination / size correction unit 14 and is subjected to correction stored in the image memory 5. It is data.

  The color correction unit 16 performs a process of removing color turbidity based on the spectral characteristics of the CMY color material including unnecessary absorption components in order to achieve faithful color reproduction.

  The black generation and under color removal unit 17 generates black (K) signals from the CMY three-color signals after color correction, and subtracts the K signals obtained by black generation from the original CMY signals to generate new CMY signals. Generate the process. As a result, the CMY three-color signal is converted into a CMYK four-color signal.

  The spatial filter processing unit 18 performs spatial filter processing using a digital filter on the image data of the CMYK signal input from the black generation and under color removal unit 17 to correct the spatial frequency characteristics. As a result, blurring of the output image and deterioration of graininess can be reduced.

  The output tone correction unit 19 performs output γ correction processing for outputting a signal such as a density signal to the color image output device 4.

  Similar to the spatial filter processing unit 18, the gradation reproduction processing unit 20 performs processing based on the region identification signal on the image data of the CMYK signal.

  For example, for a region separated into characters by the region separation processing unit 15, the spatial filter processing unit 18 uses a filter with a high enhancement amount of high frequency components as a spatial filter in order to improve the reproducibility of characters. . In the gradation reproduction processing unit 20, binarization or multilevel conversion processing is performed using a high-resolution screen suitable for reproducing high-frequency components.

  For the region separated into halftone dots by the region separation processing unit 15, the spatial filter processing unit 18 performs low-pass filter processing for removing the input halftone component. The output gradation correction unit 19 performs γ correction processing, and then the gradation reproduction processing unit 20 performs gradation reproduction processing that finally separates the image into pixels so that each gradation can be reproduced. Is done.

  For the region separated into photographs by the region separation processing unit, the tone reproduction processing unit 20 performs binarization or multi-value processing on the screen with an emphasis on tone reproducibility.

  The image data subjected to the above-described processes is temporarily stored in the image memory 5, read out from the image memory 5 at a predetermined timing, and output to the color image output device 4.

  The color image output device 4 has a function as a printer that outputs image data onto a recording medium such as paper, and examples thereof include a printing device using an electrophotographic method or an inkjet method.

  The above processing is controlled by a CPU (Central Processing Unit) (not shown) provided in the digital color copying machine 1. The image forming apparatus is not limited to the digital color copying machine 1, and may be, for example, a multi-function machine having a copy function, a printer function, a facsimile transmission function, a scan to e-mail function, and the like.

  Next, the color image input apparatus 2 that automatically conveys and reads a document will be described. FIG. 2 is a longitudinal sectional view showing an example of the structure of the color image input device 2 shown in FIG.

  A strip-shaped white plate having a predetermined width extending in the direction of the line sensor is disposed in the document reading area where the color image input device 2 reads the document. This strip-shaped white plate is not the same as the original mat when the original is placed on the original table and is read, but the rear surface of the original is white as in the case of reading the original placed on the original table and pressed by the original mat. . Thus, the configuration of the present invention processes the image data of the document read by the color image input device 2 in addition to processing the image data of the document placed on the document table and pressed by the document mat. In this case, the same applies.

  As shown in FIG. 2, the color image input apparatus 2 includes a document transport unit 31 covered with an upper housing 510 and a scanner unit 32 covered with a lower housing 560.

  The document transport unit 31 includes a document tray 511, a document set sensor 514, a drawing roller 512, transport rollers 513 a and 513 b, a feeding timing sensor 515, a document discharge roller 516, and a document discharge sensor 567. Document set sensor 514 detects the presence or absence of a document placed on document tray 511. The attracting roller 512 conveys the documents on the document tray 511 one by one.

  The conveyance rollers 513a and 513b convey the document to the reading position. Specifically, the conveyance roller 513b includes an electromagnetic clutch (not shown) on the drive shaft, and the transmission of the driving force from the drive motor (not shown) is controlled, and stops when there is no document. Yes. On the other hand, when the leading edge of the document is detected by the feeding timing sensor 515, the document rotates in the direction in which the document is conveyed downstream. The transport roller 513b is stopped and the leading edge of the document transported from the upstream side contacts the nip portion of the transport roller 513b to form a predetermined deflection, and then transports the document downstream. At this time, the leading edge of the document is aligned by the nip portion of the conveying roller 513b so as to be perpendicular to the conveying direction.

  The document discharge roller 516 discharges the document from the reading position onto the document discharge tray 566. The document discharge sensor 567 detects a document discharged on the document discharge tray 566.

  The scanner unit 32 includes scanning units 562 and 563, an imaging lens 564, a CCD line sensor 565 that is a photoelectric conversion element, and a discharge tray 566. The scanning unit 562 includes a light source 562a and a mirror 562b. The scanning unit 563 includes mirrors 563a and 563b.

  The scanning units 562 and 563 reciprocate in parallel along the lower surface of the document table 561. The light source 562a of the scanning unit 562 is made of, for example, a halogen lamp, and irradiates light on a document conveyed from the document tray 511 or a document placed on the document placing table 561. The mirror 562b guides the light reflected by the document to the scanning unit 563. The mirrors 563a and 563b of the scanning unit 563 guide the light reflected by the mirror 562b to the imaging lens 564.

  The imaging lens 564 images the reflected light guided from the scanning unit 563 at a predetermined position on the CCD line sensor 565. The CCD line sensor 565 photoelectrically converts the formed optical image and outputs an electrical signal. That is, based on a color image read from an original (for example, the surface of the original), data separated into R (red), G (green), and B (blue) color components is output to the color image processing apparatus.

  Next, the document inclination / size detection unit 21 and the document inclination / size correction unit 14 will be described. FIG. 3 is a block diagram showing a configuration of the document inclination / size detection unit 21 shown in FIG. As illustrated in FIG. 3, the document inclination / size detection unit 21 includes an edge detection processing unit 41, an angle calculation unit 42, and a document region extraction unit 43. The document area extraction unit 43 includes a coordinate information conversion unit 44 and a document area detection unit 45.

  FIG. 5 is a flowchart showing an outline of the procedure of document skew / size detection processing by the document skew / size detector 21.

  In FIG. 5, an edge detection processing unit 41 detects an edge of a document from input image data. That is, the outermost circumscribed edge (edge coordinate) of the document is detected (S1).

  When performing this processing, the edge detection processing unit 41 converts the RGB signal into a luminance Y signal as shown in the following equation.

The RGB signal may be converted into a CIE 1976 L ^* a ^* b ^* signal (CIE: Commission International de l'Eclairage, L ^* : brightness, a ^* , b ^* : chromaticity). Alternatively, the G signal may be used in the document inclination / size correction processing.

  In this process, the edge detection processing unit 41 performs a reduction process on the input image data so as to have a predetermined resolution (detection resolution) for detecting the edge of the document. Further, in each line unit of the image data (detection image data) converted to the detection resolution, a pixel position where the difference in pixel value between adjacent pixels is larger than a predetermined threshold is extracted as an edge.

  The input image data is, for example, image data of an area read by the color image input device 2 in an A3 size document. When “original inclination / size correction” (see FIG. 4) by the original inclination / size correction unit 14 is selected, the original is not necessarily placed at a predetermined position on the original table, and is also inclined. There is a possibility. In this case, the color image input apparatus 2 reads the document in the maximum readable area.

  The predetermined resolution (detection resolution) is a preset resolution that is optimal for document inclination / size detection processing, such as 75 dpi.

  The predetermined threshold is set to a numerical value such as “3”, for example, and the boundary between the document background and the document, which is an image on the lower surface of the document pressing member (document pressing member) on the document placing table 561, can be detected. Value.

  Next, the edge detection processing unit 41 stores the edge coordinates of the document extracted from the input image data in the coordinate information table shown in FIGS. FIG. 6A is an explanatory diagram illustrating a first coordinate information table that stores the upper edge coordinates, the lower edge coordinates, the upper correction edge coordinates, and the lower correction edge coordinates detected by the edge detection processing unit 41. FIG. 6B is an explanatory diagram illustrating a second coordinate information table that stores the left edge coordinate, the right edge coordinate, the left correction edge coordinate, and the right correction edge coordinate detected by the edge detection processing unit 41. It is.

  The edge detection processing unit 41 calculates the leftmost pixel coordinate when scanning in the x-axis direction as the left edge coordinate in the image of the document edge extracted from the input image data, and the rightmost pixel coordinate as the right part. Calculated as edge coordinates. The number of coordinates M (FIG. 6B) calculated in this process depends on the vertical size of the image converted to the detection resolution. Similarly, the edge detection processing unit 41 calculates the uppermost pixel coordinates when scanned in the y-axis direction as upper edge coordinates, and calculates the lowermost pixel coordinates as lower edge coordinates. The calculated coordinate number N (FIG. 6A) depends on the horizontal size of the image converted to the detection resolution.

  Next, the angle calculation unit 42 calculates the inclination angle of the document from the edge coordinates of the input image data detected by the edge detection processing unit 41 (S2). For this process, the tilt detection method described in Patent Document 1 can be used.

  Specifically, first, a change in inclination between coordinate data of each document edge is detected from the detected edge coordinates, a point (edge change point) at which the inclination changes is obtained, and a line segment connecting these edge change points is obtained. To extract.

  Next, among the extracted line segments, the longest line segment having an inclination angle of 45 ° or less with respect to the X direction (sub-scanning direction) is selected, and the selected line segment is started. The document inclination is calculated from the coordinates (StartEdgeX, StartEdgeY) and the end coordinates (EndEdgeX, EndEdgeY).

  In this case, if the document tilt angle is α,

It is. The angle α corresponding to this value is read from a previously prepared table, for example, the table (tangent-angle table) shown in FIG.

  Next, the coordinate information conversion unit 44 of the document area extraction unit 43 performs coordinate conversion processing on the edge coordinates detected by the edge detection processing unit 41 (S3). In this coordinate conversion processing, the edge coordinates detected by the edge detection processing unit 41 are corrected by the document inclination angle α calculated by the angle calculation unit 42.

  Specifically, the coordinate information conversion unit 44 corrects all the edge coordinates (EdgeX, EdgeY) detected by the edge detection processing unit 41 with the document inclination angle α calculated by the angle calculation unit 42. Is calculated by the following equation, and this is used as corrected edge coordinates (CorrEdgeX, CorrEdgeY).

  The corrected edge coordinates calculated by the coordinate information conversion unit 44 are stored in the coordinate information tables of FIGS. 6 (a) and 6 (b).

  Next, the document area detection unit 45 of the document area extraction unit 43 performs document area detection processing (S4). In this document area detection process, the document area detection unit 45 compares the document inclination angle α detected by the angle calculation unit 42 with a threshold angle for process switching, and determines the document area according to the comparison result. The detection process is switched to the first document area detection process or the second document area detection process. The threshold angle is a threshold value of the document inclination angle with respect to the normal arrangement state (document inclination angle 0 degree), and is appropriately set when switching the document area detection process, such as 2 degrees to 3 degrees. The optimal angle. The first and second document area detection processes will be described in detail later.

  Next, the document area detection unit 45 determines the correction process start coordinates (StartX, StartY) and the corrected document height in the first or second document area detection process from the corrected edge coordinates determined as the valid edges. And the width are calculated by the following method.

Correction processing start coordinates (StartX, StartY):
The minimum value of the x coordinate (CorrEdgeMinX) and the minimum value of the y coordinate (CorrEdgeMinY) in the effective correction edge coordinate are returned to the coordinate value of the actual coordinate system by the following conversion formula, and the coordinate value is the correction processing start coordinate Set as StartX, StartY.

Corrected document height:
(Maximum value of y coordinates in corrected edge coordinates) − (Minimum value of y coordinates in corrected edge coordinates).

Corrected document width:
(Maximum value of x coordinates in corrected edge coordinates) − (Minimum value of x coordinates in corrected edge coordinates)

  The document area detection unit 45 uses the correction processing start coordinates (StartX, StartY), the corrected document height and width, and the angle information detected by the angle calculation unit 42 as correction parameters, and corrects them. After being converted into a value that matches the resolution of the image data for use (resolution of the input image data), it is output as detection information (S5).

  In the present embodiment, the document size is not represented by a standard size but is expressed using the height and width of the document after correction calculated by the above processing. As the calculated height and width of the original after correction, values converted to the standard size using the paper size table for each output resolution so as to have a correspondence with the standard size paper are used. Also good. FIG. 8 is an explanatory diagram showing an example of a paper size table for a resolution of 300 dpi used when the document inclination / size detection unit 21 converts the obtained document size into a standard size.

  To determine the document size, first, compare the calculated corrected document width with the paper width of each paper size shown in the paper size table, and set the paper size range to a paper width greater than or equal to the corrected document width. The paper size is narrowed down to the minimum paper width range. Next, the corrected original height is compared with the paper height of each paper size shown in the paper size table, and the smallest paper height among the paper sizes with the paper height higher than the corrected original height is compared. Set the paper size as the output paper size.

  For example, when the corrected document width when converted to 300 dpi is 2480 and the corrected document height is 3500, first, based on the corrected document width, the paper size range is set to a sheet width of 2480 or more. The paper size is narrowed down to A4 or A5R which is the paper size in the minimum paper width range. Next, based on the corrected document height, A4 which is the smallest paper height among paper sizes of 3500 or more is set as the output paper size.

  Note that the set value of the output paper size table is set to the number of pixels that is about 10 mm larger than the actual size in consideration of the error of the size detection result.

  Next, document area detection processing by the document area detection unit 45 will be described in detail with reference to FIGS. 9 and 10A to 10C. FIG. 9 is a flowchart showing the operation of document area detection processing by the document area detection unit 45. 10A is an explanatory diagram of the process of S14 in FIG. 9, FIG. 10B is an explanatory diagram of the process of S19 in FIG. 9, and FIG. 10C is an explanatory diagram of the process of S22 in FIG. It is.

  As described above, the edge coordinate information (left edge coordinates, right edge coordinates, upper edge coordinates, lower edge coordinates) of the document (input image data) extracted by the edge detection processing unit 41 for detecting the document size. Is corrected by using the angle information indicating the inclination angle of the document (input image data) detected by the angle calculation unit 42 and the coordinate information conversion unit 44 performs the inclination correction, thereby correcting the corrected edge coordinate information ( Left correction edge coordinates, right correction edge coordinates, upper correction edge coordinates, lower correction edge coordinates). The document area detection unit 45 extracts an effective document edge (effective edge) by the following processing based on the corrected edge coordinate information.

First, for each of the upper and lower corrected edge coordinates, the corrected edge coordinate located at the end is set as the target coordinate, and the 2 ⁿ (1, 2, 4, 8,...) Position counted from the position of the target coordinate. The difference value of the y coordinate between the corrected edge coordinate and the target coordinate is obtained. Alternatively, the difference value of the y coordinate between the corrected edge coordinate of the 2 ⁿ (4, 8,...) Position and the target coordinate is counted from the position of the target coordinate excluding the pixel at the position close to the target pixel. Ask for each. Then, a case where the difference value is equal to or less than a threshold value (for example, “2 pixels”) is counted, and this count value is set as an effective count for the corresponding edge. Hereinafter, the attention coordinate is sequentially moved to the adjacent correction edge coordinate, and the processing is repeated until the same processing is completed for all the correction edge coordinates. Thus, an effective count value is obtained for each edge coordinate (S11).

  Next, for each of the upper correction edge and the lower correction edge, an effective count of an edge having an effective count value larger than a preset extraction effective count parameter (for example, “2”) with respect to the effective count of each correction edge coordinate. Average value (upper correction edge effective count average value: AveEdgeCountT, lower correction edge effective count average value: AveEdgeCountB) and the largest effective count value (upper correction edge maximum effective count value: MaxEdgeCountT, lower correction edge maximum effective count value) : MaxEdgeCountB) is calculated (S12).

  Next, of the upper correction edge information having an effective count value equal to or higher than the upper correction edge effective count average value (AveEdgeCountT), the edge having the smallest y coordinate is set as the upper maximum effective edge. Further, among the lower correction edge information having an effective count value equal to or higher than the lower correction edge effective count average value (AveEdgeCountB), the edge having the largest y coordinate is set as the lower maximum effective edge (S13).

  Next, the difference between the y coordinate of the correction edge coordinate of the upper maximum effective edge and the y coordinate of each upper correction edge coordinate is obtained, and the upper edge where the difference is below the set range (for example, “two pixels” or less) It is determined that it exists on the extension line of the effective edge, and is set as the effective edge. The other edges are set as invalid edges (see FIG. 10A). The valid edge and invalid edge are similarly determined for the lower edge (S14).

  Next, regarding the left and right corrected edge information, the same processing as S11 is performed on the x coordinate, and an effective count is generated for each edge coordinate (S15).

  Next, with respect to the left and right corrected edge information, the same processing as in S12 is performed, and the average value of the effective counts of the edges having an effective count value larger than the extracted effective count parameter (eg, “2”) Edge effective count average value: AveEdgeCountL, right correction edge effective count average value: AveEdgeCountR) and the largest effective count value (left correction edge maximum effective count value: MaxEdgeCountL, right correction edge maximum effective count value: MaxEdgeCountR) Calculate (S16).

  Next, it is determined whether or not the detection angle is greater than or equal to a threshold value (S17). If the detection angle is greater than or equal to the threshold value, the first document area detection process of S18 is performed, and if the detection angle is less than the threshold value. The second document area detection process of S19 to S20 is performed.

  In the first document area detection process, in S18, the same process as in S13 is performed on the left correction edge information and the right correction edge information, and the left maximum effective edge and the right maximum effective edge are set.

  In the second document area detection process, as shown in FIG. 10B, in S19, three types of maximum valid edge candidates (first to third maximum edges) are associated with the left correction edge information and the right correction edge information. Effective edge candidate) is set.

  The first maximum valid edge candidate is set by the same process as the first document area detection process of S18.

  The second maximum valid edge candidate (second process) includes an upper effective correction edge (effective edge after coordinate conversion (effective correction edge)) and a lower effective correction edge (effective edge after coordinate conversion (effective correction). Edge)) and the outermost edge of the corrected edge information that has a count value greater than or equal to the left edge correction edge effective count average value (AveEdgeCountL) and right edge correction edge effective count average value (AveEdgeCountR) Set the edge.

  The third maximum valid edge candidate (first processing) is an edge within a specific range centered on the ends of the upper valid correction edge and the lower valid correction edge, and the left corrected edge valid count average value (AveEdgeCountL) and Out of the corrected edge information having a count value equal to or greater than the right correction edge effective count average value (AveEdgeCountR), the outermost edge is set.

  Next, in S20, from the first to third maximum effective edge candidates (first to third left and right maximum effective edge candidates), any one maximum effective edge candidate (left and right maximum) Effective edge candidate) is selected.

  In this selection, the third maximum valid edge candidate (first process) is extracted with a limited range using the information of the upper and lower edges, and therefore has the highest reliability. Therefore, when the third maximum effective edge candidate exists, this edge is set as the maximum effective edge. In other words, the process using the third maximum effective edge candidate (first process) is performed using a document area more than the first document area detecting process and the process using the second maximum effective edge candidate (second process). It is determined whether each detected edge is an effective edge that can be regarded as an edge of a document image or noise under conditions that limit the detection range.

  The second maximum valid edge candidate is extracted so as to include the outer edge as much as possible in order to eliminate content missing as much as possible. Therefore, when there is no third maximum effective edge candidate, this edge is set as the maximum effective edge.

  The first maximum valid edge candidate is extracted so as not to cause missing content in the document even if the actual document edge cannot be extracted. Therefore, this edge is set as the maximum effective edge only when both the third and second maximum effective edge candidates do not exist.

  As described above, the selection priority of the first to third maximum effective edge candidates is in the order of the third maximum effective edge candidate → the second maximum effective edge candidate → the first maximum effective edge candidate.

  Next, the left edge correction edge information and the right edge correction edge information determined by the first or second document area detection process are subjected to the same processing as S14 to determine the valid edge and the invalid edge (S21). .

  Next, as shown in FIG. 10C, isolated point noise may be included in those determined as valid edges in S21. Therefore, here, a process of separating the edge determined as the effective edge in S21 into the effective edge and the isolated point noise is performed (S22).

  In this process, among those determined as valid edges in S21, the left and right edges existing outside the upper and lower edges of the document, and the outer edges of the left and right edges of the document. For the existing upper edge and lower edge, using the effective edge information around the edge (processing target edge), that is, depending on the number of effective edges around the edge (processing target edge), the processing target edge Is a valid edge or isolated noise.

  In the above determination, for example, when the number of effective edges around the processing target edge is greater than or equal to a predetermined value, the processing target edge is determined as an effective edge. On the other hand, when the number of effective edges around the processing target edge is less than a predetermined value, the processing target edge is determined as isolation rate noise.

  The document skew / size correction parameter generated in the document skew / size detection unit 21 as described above is input to the document skew / size correction unit 14. The document inclination / size correction unit 14 corrects the inclination and size of the document with respect to the RGB data (input image data) input from the input gradation correction unit 13 based on the document inclination / size correction parameter. FIG. 11 is a flowchart showing an outline of document skew / size correction processing in the document skew / size corrector 14.

  The document inclination / size correction unit 14 outputs, from the image memory 5, input image data (scan data) including RGB signals, that is, the input gradation correction unit 13, to the image memory 5 in the document inclination / size correction processing. The stored image data is read (S101).

  Next, document skew / size correction processing is performed on the read input image data (S102).

  As document skew / size correction processing, affine transformation processing using a rotation matrix is generally used.

  In general, coordinates (x ′, y ′) obtained by rotating coordinates (x, y) by θ are expressed by a rotation determinant represented by the following equation.

  Therefore, when outputting as the pixel value of the image, the decimal value (xs, ys) is derived from the integer value (x ′, y ′), and this is interpolated by bilinear or the like. The inverse transformation formula of the above formula (5) is the following formula (6).

From this equation (6), (xs, ys) necessary for obtaining (x ′, y ′) can be found.

In the xy coordinate system before rotation correction, four pixel values including (xs + StartX, ys + StartY) are input. Now, x _i ≦ xs + StartX <x _{i + 1} , y _i ≦ ys + StartY <y _{i + 1} , and the distance ratio is u: 1-u, v: 1-v (where u and v are Both are numerical values of 0 or more and less than 1), and the values of each of the surrounding four pixels are (x _i , y _i ): Z ₁ , (x _{i + 1} , y _i ): Z ₂ , (x _i , y _{When i + 1} ): Z ₃ and (x _{i + 1} , y _{i + 1} ): Z ₄ , the coordinate value Z after bilinear interpolation is obtained by the following equation (7) (see FIG. 12). FIG. 12 is an explanatory diagram illustrating an example of calculating the rotation source coordinate value used in the document tilt / size correction process of the document tilt / size correction unit 14.

The trigonometric ratio value used here can be calculated at high speed by using a table as shown in FIG. (X ', y') after rotation correction is
0 ≦ x ′ <corrected document width, 0 ≦ y ′ <corrected document height.

  In the digital color copying machine 1 according to the present embodiment, the original inclination / size correction processing by the original inclination / size detection unit 21 and the original inclination / size correction processing by the original inclination / size correction unit 14 are performed in the original inclination / size correction mode. This is done by setting. As shown in FIG. 4, the original skew / size correction mode is set to “original skew / size correction” in the special function display initial menu displayed on the LCD display unit 51 of the operation panel of the digital color copying machine 1. It is done by being selected.

  When “original skew / size correction” is selected, a menu screen shown in FIG. 13 is first displayed on the LCD display unit 51. In this screen, the user selects “original skew / size correction” with “ You can select “Always set” or “Confirm every scan”. When “Always set” is selected, document skew / size detection processing and document tilt / size correction processing are always performed when copying, when reading and transmitting a document, and when filing a document image.

  As described above, the digital color copying machine 1 does not perform document area detection processing uniformly on image data, but performs first document area detection processing depending on whether the inclination angle of the document image is greater than or less than a threshold value. And the second document area detection process. In this case, the second document area detection process selected when the inclination angle of the document image is less than the threshold value detects a document area for each edge of the document image more than the first document area detection process. Whether the edge is a valid edge or noise that can be regarded as an edge of the document image is determined under a condition that limits the range to be processed. Thus, even when the original is read with the original reading apparatus in a state in which the inclination angle is small with respect to the normal arrangement state, the vertical streak of the outside area of the original generated when the original is read. Thus, it is possible to detect the document size with high accuracy by avoiding erroneous detection due to noise such as the above. Further, since the background of the document is a white plate, it is possible to accurately detect the document size even for a document image in which it is difficult to detect the edge of the document image at the boundary between the document itself and the white plate.

[Embodiment 2]
Another embodiment of the present invention will be described below with reference to the drawings. FIG. 14 is a block diagram showing another example of the digital color copying machine 1 shown in FIG.

  In the digital color copying machine (image forming apparatus) 7 shown in FIG. 2, the color image processing apparatus 3 shown in FIG. 1 is divided into a color image processing apparatus front part 3a and a color image processing apparatus rear part 3b. The pre-stage unit 3a of the color image processing apparatus includes an A / D conversion unit 11, a shading correction unit 12, an input tone correction unit 13, and a document inclination / size detection unit 21. A size correction unit 14, a region separation processing unit 15, a color correction unit 16, a black generation and under color removal unit 17, a spatial filter processing unit 18, an output gradation correction unit 19, and a gradation reproduction processing unit 20 are included.

  Further, between the color image processing apparatus front-stage unit 3a and the color image processing apparatus rear-stage unit 3b, specifically, the input tone correction unit 13 and the document inclination / size detection unit 21 of the color image processing apparatus front-stage unit 3a and the color. An image storage device (HDD) 35 is provided between the image processing apparatus rear stage unit 3 b and the document inclination / size correction unit 14.

  The color image processing device front-stage unit 3 a stores the processed data in the image storage device 35. The color image processing apparatus post-stage unit 3b reads the data processed by the color image processing apparatus pre-stage unit 3a from the image storage device 35 and processes the data. The color image processing apparatus front stage unit 3a and the color image processing apparatus rear stage unit 3b can operate asynchronously.

  When the document skew / size correction process is selected, the document skew / size detection unit 21 of the pre-stage unit 3a of the color image processing apparatus uses the document skew / size correction parameter α and the document size correction parameter (after correction) as detection information. A document size and correction processing start coordinates) are obtained and stored in the image storage device 35 in association with the corresponding image data stored in the image storage device 35.

  On the other hand, the post-stage unit 3b of the color image processing apparatus 3a, the image data after the input tone correction stored in the image storage device 35, the document inclination correction angle parameter α of the detection information stored in association therewith, and the document size The correction parameters (corrected document size and correction processing start coordinates) are read out, the above-described coordinate conversion is performed by the document inclination / size correction unit 14, and the results are sequentially stored in the image memory 6.

  The region separation processing unit 15 performs region separation processing on the data after inclination / size correction stored in the image memory 6. Subsequent processing units proceed with the pipeline method. By these operations, the color image processing apparatus front stage unit 3a and the color image processing apparatus back stage unit 3b can perform processing asynchronously.

[Embodiment 3]
Still another embodiment of the present invention will be described below with reference to the drawings. FIG. 15 is a block diagram showing a configuration of an image reading apparatus (scanner) 8 including the document inclination / size detection unit 21 and the document inclination / size correction unit 14 shown in FIG.

  The image reading device 8 includes a color image input device 2, a color image processing device 9, an image memory 5, and an image storage device 35.

  The color image processing apparatus 9 includes an A / D conversion unit 11, a shading correction unit 12, an input tone correction unit 13, a document inclination / size detection unit 21, a document inclination / size correction unit 14, and a selector 36.

  When “original skew / size correction” is selected in the color image processing apparatus 9, the original skew / size detection unit 21 calculates the detection information described above and temporarily stores the detection information in the image memory 5. Thereafter, the document inclination / size correction unit 14 reads the detection information and the image data from the image memory 5, corrects the inclination / size of the image data, and stores the corrected image data in the image memory 5. When the processing of the image data for one page is completed in this way, the image data is read from the image memory 5 and stored in the image storage device 35 via the selector 36.

  On the other hand, when “original skew / size correction” is not selected, the RGB data after the input gradation processing correction by the input gradation correction unit 13 is stored in the image storage device 35 via the selector 32.

As described above, when “original skew / size correction” is selected, the selector 36 stores the image data processed by the original skew / size detector 21 and the original skew / size corrector 14 in the image storage device 35. Output to. On the other hand, if “Original skew / size correction” is not selected,
The image data processed by the input tone correction unit 13 is output to the image storage device 35.

  The color image processing device 9 does not output the image data processed by the document skew / size correction unit 14 to the image storage device 35, but a computer, server, digital multifunction peripheral, printer connected via a network. Or the like.

  Also, the selection of “original skew / size correction” is not selected on the operation panel, but on the scanner driver setting screen (scanner reading condition setting screen) of the computer connected to the image reading device 8, the mouse is selected. Or using a keyboard.

  The present invention performs the above-described document inclination / size determination on a computer-readable recording medium on which program code (executable program, intermediate code program, source program) to be executed by a computer is recorded, and performs rotation processing on the document. An image processing method may be recorded.

  As a result, it is possible to provide a portable recording medium on which a program for performing an image processing method for determining the inclination and size of the document and performing rotation processing on the document is carried.

  In the present embodiment, the recording medium may be a program medium such as a memory (not shown) such as a ROM itself because processing is performed by a microcomputer. However, it may be a program medium provided with a program reading device as an external storage device and readable by inserting a recording medium therein.

  In any case, the stored program code may be configured to be accessed and executed by a microprocessor, or in any case, the program code is read and the read program code is a microcomputer. The program code may be downloaded to a program storage area (not shown) and executed. It is assumed that this download program is stored in the main device in advance.

  Here, the program medium is a recording medium configured to be separable from the main body, such as a tape system such as a magnetic tape or a cassette tape, a magnetic disk such as a floppy disk (registered trademark) or a hard disk, or a CD-ROM / MO /. MD / DVD optical discs, IC cards (including memory cards) / optical cards, etc. Mask ROM, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), flash It may be a medium that carries a fixed program code including a semiconductor memory such as a ROM.

  In the present embodiment, since the system configuration is capable of connecting to a communication network including the Internet, the medium may be a medium that dynamically carries the program code so as to download the program code from the communication network. When the program code is downloaded from the communication network in this way, the program for downloading may be stored in the main device in advance or installed from another recording medium. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

  The recording medium is read by a program reading device provided in a digital color image forming apparatus or a computer system, whereby the above-described image processing method is executed.

  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 above 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 network card, a modem, and the like are provided as communication means for connecting to a server or the like via a network.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

1 Digital color copier (image forming device)
2 Color image input device (image reading device)
DESCRIPTION OF SYMBOLS 3 Color image processing apparatus 3a Color image processing apparatus front | former part 3b Color image processing apparatus back | latter stage part 4 Color image output apparatus (printing apparatus)
7 Digital color copier (image forming device)
8 Image Reading Device 14 Document Inclination / Size Correction Unit 21 Document Inclination / Size Detection Unit 31 Document Conveying Unit 41 Edge Detection Processing Unit 42 Angle Calculation Unit 43 Document Area Extraction Unit 44 Coordinate Information Conversion Unit 45 Document Area Detection Unit 51 LCD Display Unit

Claims (8)

A document inclination / size detection unit that detects the inclination and size of the document image indicated by the image data obtained by reading the document, and a document image in the image data based on the detection result of the document inclination / size detection unit In an image processing apparatus comprising an original inclination / size correction unit for correcting the inclination and original size of
The document inclination / size detection unit detects the upper and lower and left and right edges of the document image, and obtains edge coordinates indicating the position of the edge;
An angle calculation unit that calculates an inclination angle of the document image based on the edge coordinates;
A coordinate information conversion unit that converts the edge coordinates into corrected edge coordinates in a state where there is no inclination of the original image, based on the calculated inclination angle of the original image;
A document area detection unit that calculates information indicating the size of the document from the corrected edge coordinates by document area detection processing;
The document area detection unit compares the inclination angle of the document image calculated by the angle calculation unit with a threshold value, and performs a first document area detection process when the inclination angle of the document image is equal to or greater than the threshold value. When the inclination angle of the original image is less than the threshold value, a second original area detection process is performed.
In the first document area detection processing, whether each edge detected by the edge detection processing unit is an effective edge that can be regarded as an edge of the document image or noise using the corrected edge coordinates is determined. In the second document area detection process, the corrected edge coordinates are used for each edge detected by the edge detection processing unit, while determining and calculating information indicating the document size based only on the valid edge. Then, it is determined whether the edge is a valid edge or noise that can be regarded as an edge of the document image on the condition that the range for detecting the document region is limited as compared with the first document region detection process, and only the valid edge is determined. An image processing apparatus that calculates information indicating the size of the document based on the information.   The document area detection unit includes a first process and a second process as the second document area detection process. In the first process, a range in which the document area is detected more than the second process. Is determined as a valid edge that can be regarded as an edge of the document image or noise, the first process is performed with priority over the second process, and the first process is performed. The image processing apparatus according to claim 1, wherein the second process is performed when information indicating the size of the document cannot be calculated by the process.   The document area detection unit includes a first process and a second process as the second document area detection process, and the document process is wider in the second process than in the first process. It is determined whether the edge is an effective edge that can be regarded as an edge of the document image or noise, and the first process is prioritized over the second process. In the first process, The image processing apparatus according to claim 1, wherein the second process is performed when information indicating the size of the document cannot be calculated.   The document area detection unit performs the first document area detection process when the first process of the second document area detection process and the information indicating the size of the document cannot be calculated by the second process. The image processing apparatus according to claim 2, wherein the image processing apparatus performs the processing.   An image forming apparatus comprising: the image processing apparatus according to claim 1; and a printing apparatus that prints image data output from the image processing apparatus. An original in the image data based on the original inclination / size detection step for detecting the inclination and original size of the original image indicated by the image data obtained by reading the original, and the detection result in the original inclination / size detection step In an image processing method comprising an original inclination / size correction step for correcting an inclination and original size of an image,
The document inclination / size detection step detects the upper and lower and left and right edges of the document image, and obtains edge coordinates indicating the position of the edge;
An angle calculating step of calculating an inclination angle of the document image based on the edge coordinates;
A coordinate information conversion step for converting the edge coordinates into corrected edge coordinates in a state in which there is no inclination of the original image, based on the calculated inclination angle of the original image;
A document area detection step of calculating information indicating the size of the document from the corrected edge coordinates by a document area detection process;
In the document area detection step, the inclination angle of the document image calculated in the angle calculation step is compared with a threshold value, and if the inclination angle of the document image is equal to or greater than the threshold value, a first document area detection process is performed. When the inclination angle of the original image is less than the threshold value, a second original area detection process is performed.
In the first document area detection processing, whether each edge detected in the edge detection processing step is an effective edge or noise that can be regarded as an edge of the document image using the corrected edge coordinates. In the second document area detection process, the corrected edge coordinates are used for each edge detected in the edge detection process while determining and calculating information indicating the size of the document based only on the valid edge. Then, it is determined whether the edge is a valid edge or noise that can be regarded as an edge of the document image on the condition that the range for detecting the document region is limited as compared with the first document region detection process, and only the valid edge is determined. And calculating information indicating the size of the document based on the image processing method.   The program for functioning a computer as each said hand part of the image processing apparatus of any one of Claim 1 to 4.   A computer-readable recording medium on which the program according to claim 7 is recorded.

Images