Image processing apparatus, image processing method, program, recording medium, and image forming apparatus having the same

Claim 2

An image processing apparatus comprising: edge determination means for determining whether or not each pixel of an input image is an edge pixel; object-image extraction means for extracting an object image section having pixels of a predetermined pixel value or more from the input image; first-characteristic-amount calculation means for calculating a first characteristic amount that represents a characteristic of the object image section contained in a first local pixel block containing a prescribed first target pixel on the basis of the result of extraction by the object-image extraction means; edge-class determination means for determining which of a plurality of edge classes the first target pixel belongs to, on the basis of the result of determination by the edge determination means and the first characteristic amount calculated by the first-characteristic-amount calculation means; second-characteristic-amount calculation means for calculating a second characteristic amount that represents a characteristic of an image of a second local pixel block containing a prescribed second target pixel on the basis of the result of classification by the edge-class determination means; and image-class determination means for determining which of a plurality of image classes the second target pixel belongs to, on the basis of the second characteristic amount calculated by the second-characteristic-amount calculation means.

Claim 3

The image processing apparatus of claim 1 , wherein the edge determination means includes a second-derivative operation section for performing a second derivative operation for each pixel and a zero-cross determination section for determining a zero-crossing pixel as an edge pixel on the basis of the result of the second derivative operation by the second-derivative operation section.

Claim 4

The image processing apparatus of claim 1 , wherein the edge determination means includes a smoothing section for performing smoothing filter processing for each pixel, a difference-value calculating section for obtaining the difference between the result of smoothing by the smoothing section and each pixel value, and a zero-cross determination section for determining a zero-crossing pixel as an edge pixel on the basis of the difference value calculated by the difference-value calculating section.

Claim 5

The image processing apparatus of claim 1 , wherein the object-image extraction means includes a threshold setting section for setting an object-image extracting threshold, and an extracting section for comparing the value of each pixel in the first local pixel block containing the prescribed first target pixel with the object-image extracting threshold to divide them into two image sections and extracting either one of the image sections as an object image section.

Claim 6

The image processing apparatus of claim 4 , wherein the threshold setting section includes a block-characteristic-amount calculating section for calculating an in-block characteristic amount that represents the characteristic of the first local pixel block, and a threshold setting section for setting the object-image extracting threshold on the basis of the in-block characteristic amount calculated by the block-characteristic-amount calculating section.

Claim 7

The image processing apparatus of claim 4 , wherein the threshold setting section of the object-image extraction means sets a plurality of object-image extracting thresholds on the basis of the first local pixel block, and wherein the extracting section of the object-image extraction means includes a candidate extracting section for comparing the value of each pixel in the first local pixel block with the object-image extracting threshold to divide them into two image sections and extracting either one of the image sections as an candidate for the object image section, and a selecting section for selecting an object image section in which the number of pixels is closest to a predetermined number of pixels from the candidates for the object image section extracted by the candidate extracting section.

Claim 8

The image processing apparatus of claim 1 , wherein the object-image extraction means includes a histogram calculating section for calculating a cumulative-pixel-value histogram for the pixels in the first local pixel block, a threshold setting section for setting an object-image extracting threshold on the basis of the cumulative-pixel-value histogram calculated by the histogram calculating section, and an extracting section for comparing the value of each pixel in the first local pixel block with the object-image extracting threshold to divide them into two image sections and extracting either one of the image sections as the object image section.

Claim 9

The image processing apparatus of claim 1 , wherein the first-characteristic-amount calculation means is run-length calculation means for calculating a run length of the object image section extracted by the object-image extraction means.

Claim 10

The image processing apparatus of claim 1 , wherein the first-characteristic-amount calculation means is circularity calculation means for calculating the circularity of the object image section extracted by the object-image extraction means.

Claim 11

The image processing apparatus of claim 1 , wherein the second-characteristic-amount calculation means calculates a run length of the edge pixels as a second characteristic amount.

Claim 12

The image processing apparatus of claim 10 , wherein the second-characteristic-amount calculation means calculates a run length of non-edge pixels in addition to the run length of the edge pixels as a second characteristic amount.

Claim 13

The image processing apparatus of claim 1 , wherein the second-characteristic-amount calculation means calculates the second characteristic amount on the basis of the number of the edge pixels of each edge class.

Claim 14

An image forming apparatus comprising: an image processing apparatus including: edge determination means for determining whether or not each pixel of an input image is an edge pixel; object-image extraction means for extracting an object image section having pixels of a predetermined pixel value or more from the input image; first-characteristic-amount calculation means for calculating a first characteristic amount that represents a characteristic of the object image section contained in a first local pixel block containing a prescribed first target pixel on the basis of the result of extraction by the object-image extraction means; edge-class determination means for determining which of a plurality of edge classes the first target pixel belongs to, on the basis of the result of determination by the edge determination means and the first characteristic amount calculated by the first-characteristic-amount calculation means; second-characteristic-amount calculation means for calculating a second characteristic amount that represents a characteristic of an image of a second local pixel block containing a prescribed second target pixel on the basis of the result of classification by the edge-class determination means; and image-class determination means for determining which of a plurality of image classes the second target pixel belongs to, on the basis of the second characteristic amount calculated by the second-characteristic-amount calculation means.

Claim 15

An image forming apparatus comprising: an image processing apparatus including: edge determination means for determining whether or not each pixel of an input image is an edge pixel; object-image extraction means for extracting an object image section having pixels of a predetermined pixel value or more from the input image; first-characteristic-amount calculation means for calculating a first characteristic amount that represents a characteristic of the object image section contained in a first local pixel block containing a prescribed first target pixel on the basis of the result of extraction by the object-image extraction means; edge-class determination means for determining which of a plurality of edge classes the first target pixel belongs to, on the basis of the result of determination by the edge determination means and the first characteristic amount calculated by the first-characteristic-amount calculation means; second-characteristic-amount calculation means for calculating a second characteristic amount that represents a characteristic of an image of a second local pixel block containing a prescribed second target pixel on the basis of the result of classification by the edge-class determination means; and image-class determination means for determining which of a plurality of image classes the second target pixel belongs to, on the basis of the second characteristic amount calculated by the second-characteristic-amount calculation means.

Claim 16

An image processing method comprising: an edge determination process for determining whether or not each pixel of an input image is an edge pixel; an object-image extraction process for extracting an object image section composed of pixels having a predetermined pixel values or more from the input image; a first-characteristic-amount calculation process for calculating a first characteristic amount that represents a characteristic of an object image section contained in a first local pixel block containing a predetermined first target pixel on the basis of the result of extraction by the object-image extraction process; an edge-class determination process for determining which of a plurality of edge classes the first target pixel belongs to, on the basis of the result of determination by the edge determination process and the first characteristic amount calculated in the first-characteristic-amount calculation process; a second-characteristic-amount calculation process for calculating a second characteristic amount that represents a characteristic of an image in the second local pixel block containing a predetermined second target pixel on the basis of the result of classification by the edge-class determination process; and an image-class determination process for determining which of the plurality of image classes the second target pixel belongs to, on the basis of the second characteristic amount calculated in the second-characteristic-amount calculation process.

Claim 17

An image processing method comprising: an edge determination process for determining whether or not each pixel of an input image is an edge pixel; an object-image extraction process for extracting an object image section composed of pixels having a predetermined pixel values or more from the input image; a first-characteristic-amount calculation process for calculating a first characteristic amount that represents a characteristic of an object image section contained in a first local pixel block containing a predetermined first target pixel on the basis of the result of extraction by the object-image extraction process; an edge-class determination process for determining which of a plurality of edge classes the first target pixel belongs to, on the basis of the result of determination by the edge determination process and the first characteristic amount calculated in the first-characteristic-amount calculation process; a second-characteristic-amount calculation process for calculating a second characteristic amount that represents a characteristic of an image in the second local pixel block containing a predetermined second target pixel on the basis of the result of classification by the edge-class determination process; and an image-class determination process for determining which of the plurality of image classes the second target pixel belongs to, on the basis of the second characteristic amount calculated in the second-characteristic-amount calculation process.

Claim 18

The image processing method of claim 14 , wherein the edge determination process includes a second derivative operation process for performing a second derivative operation for each pixel and a zero-cross determination process for determining a zero-crossing pixel as an edge pixel on the basis of the result of the second derivative operation in the second derivative operation process.

Claim 19

The image processing method of claim 14 , wherein the edge determination process includes a smoothing process for performing smoothing filter processing for each pixel, a difference-value calculation process for obtaining the difference between the result of smoothing in the smoothing process and each pixel value, and a zero-cross determination process for determining a zero-crossing pixel as an edge pixel.

Claim 20

The image processing method of claim 14 , wherein the object-image extraction process includes a threshold setting process for setting an object-image extracting threshold and an extraction process for comparing the value of each pixel in the first local pixel block that contains a predetermined first target pixel with the object-image extracting threshold to divide them into two image sections and extracting either one of the image sections as an object image section.

Claim 21

The image processing method of claim 17 , wherein the threshold setting process includes a block-characteristic-amount calculation process for calculating an in-block characteristic amount that represents the characteristic of the first local pixel block and an order-threshold setting process for setting an object-image extracting threshold on the basis of the in-block characteristic amount calculated in the block-characteristic-amount calculation process.

Claim 22

The image processing method of claim 17 , wherein in the threshold setting process of the object-image extraction process, a plurality of object-image extracting thresholds is set on the basis of the first local pixel block, and wherein the extraction process in the object-image extraction process includes a candidate extraction process for comparing the value of each pixel in the first local pixel block with the object-image extracting threshold for each object-image extraction threshold, dividing them into two image sections, and thereby extracting either one of the image sections as a candidate for the object image section, and a selection process for selecting an object image section having a pixel value closest to a prescribed pixel value from the candidates for the object image section which are extracted in the candidate extraction process.

Claim 23

The image processing method of claim 14 , wherein the object-image extraction process includes a histogram calculation process of calculating the cumulative-pixel-value histogram for the pixels in the first local pixel block; a threshold setting process for setting an object-image extracting threshold on the basis of the cumulative-pixel-value histogram calculated in the histogram calculation process; and an extraction process for comparing the value of each pixel in the first local pixel block with the object-image extracting threshold to divide them into two image sections and extracting either one of the image sections as an object image section.

Claim 24

The image processing method of claim 14 , wherein the first-characteristic-amount calculation process is a run-length calculation process for calculating a run length of the object image section extracted in the object-image extraction process.

Claim 25

The image processing method of claim 14 , wherein the first-characteristic-amount calculation process is a circularity calculation process for calculating the circularity of the object image section extracted in the object-image extraction section.

Claim 26

The image processing method of claim 14 , wherein in the second-characteristic-amount calculation process, a run length of the edge pixels is calculated as a second characteristic amount.

Claim 27

The image processing method of claim 23 , wherein in the second-characteristic-amount calculation process, in addition to the run length of the edge pixels, a run length of non-edge pixels is calculated as a second characteristic amount.

Claim 28

The image processing method of claim 14 , wherein in the second-characteristic-amount calculation process, the second characteristic amount is calculated on the basis of the number of the edge pixels of each edge class.

Claim 29

A computer-readable recording medium which records a program for causing a computer to execute image processing method comprising: an edge determination process for determining whether or not each pixel of an input image is an edge pixel; an object-image extraction process for extracting an object image section composed of pixels having a predetermined pixel values or more from the input image; a first-characteristic-amount calculation process for calculating a first characteristic amount that represents a characteristic of an object image section contained in a first local pixel block containing a predetermined first target pixel on the basis of the result of extraction by the object-image extraction process; an edge-class determination process for determining which of a plurality of edge classes the first target pixel belongs to, on the basis of the result of determination by the edge determination process and the first characteristic amount calculated in the first-characteristic-amount calculation process; a second-characteristic-amount calculation process for calculating a second characteristic amount that represents a characteristic of an image in the second local pixel block containing a predetermined second target pixel on the basis of the result of classification by the edge-class determination process; and an image-class determination process for determining which of a plurality of image classes the second target pixel belongs to, on the basis of the second characteristic amount calculated in the second-characteristic-amount calculation process.

Claim 30

A computer-readable recording medium which records a program for causing a computer to execute image processing method comprising: an edge determination process for determining whether or not each pixel of an input image is an edge pixel; an object-image extraction process for extracting an object image section composed of pixels having a predetermined pixel values or more from the input image; a first-characteristic-amount calculation process for calculating a first characteristic amount that represents a characteristic of an object image section contained in a first local pixel block containing a predetermined first target pixel on the basis of the result of extraction by the object-image extraction process; an edge-class determination process for determining which of a plurality of edge classes the first target pixel belongs to, on the basis of the result of determination by the edge determination process and the first characteristic amount calculated in the first-characteristic-amount calculation process; a second-characteristic-amount calculation process for calculating a second characteristic amount that represents a characteristic of an image in the second local pixel block containing a predetermined second target pixel on the basis of the result of classification by the edge-class determination process; and an image-class determination process for determining which of a plurality of image classes the second target pixel belongs to, on the basis of the second characteristic amount calculated in the second-characteristic-amount calculation process.