Image processing apparatus, image forming apparatus, image processing system, and image processing method

• US 8,180,159 B2
• Filed: 06/05/2008
• Issued: 05/15/2012
• Est. Priority Date: 06/06/2007
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Hayasaki, Makoto
• Primary Examiner(s): Repko, Jason M
• Assistant Examiner(s): PERLMAN, DAVID S
• Application Number:
  US12/133,940
• Publication Number:
  US 20080310730A1
• Time in Patent Office: 1,440 Days
• Field of Search: None
• US Class Current: 382/216
• CPC Class Codes: G06V 10/245 by locating a pattern; Special marks for positioning
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/18143 Extracting features based on salient regional features, e.g. scale invariant feature transform [SIFT] keypoints

Abstract

There are provided: a pattern detection process section for extracting a partial image made of pixels including a target pixel from input image data; a displaced image generation section for generating a self-displaced image by displacing at least a part of the partial image through a predetermined method; and a matching test determination section for determining whether an image pattern included in the partial image matches an image pattern included in the self-displaced image or not. When the matching test determination section determines that the matching exists, a target pixel in the partial image or a block made of pixels including the target pixel is regarded as a feature point. Consequently, even when image data is subjected to a process such as enlarging and reducing, it is possible to extract a feature point that properly specifies the image data regardless of the enlarging/reducing process.

Claims

1. An image processing apparatus, comprising:

a feature point detection section for detecting feature points included in input image data; and

a features calculation section for calculating features of the input image data in accordance with relative positions of the feature points detected by the feature point detection section,

the feature point detection section including;

a partial image extraction section for extracting, from the input image data, a partial image made of a plurality of pixels including a target pixel, an index for indicating busyness of the partial image being not less than a predetermined threshold value;

a displaced image generation section for generating a self-displaced image by displacing at least a part of the partial image, which has been extracted by the partial image extraction section, with other part of the partial image;

a matching test determination section for determining whether an image pattern included in the partial image matches an image pattern included in the self-displaced image or not; and

a detection section for detecting, as each of the feature points, (a) a target pixel in the partial image including the image pattern determined by the matching test determination section as matching the image pattern included in the self-displaced image, or (b) a block made of a plurality of pixels including the target pixel.

2. The image processing apparatus as set forth in claim 1, wherein the self-displaced image generated by the displaced image generation section is (a) a line symmetrical displaced image obtained by displacing a pixel value of each pixel of the partial image with a pixel value of a pixel that is symmetrical with said each pixel in respect to a line passing through the partial image, or (b) a point-symmetrical displaced image obtained by displacing a pixel value of each pixel of the partial image with a pixel value of a pixel that is symmetrical with said each pixel in respect to a point in the partial image.

3. The image processing apparatus as set forth in claim 1, further comprising:

at least one of a storage section in which features of a reference image are stored and a reference image obtaining section for obtaining the features of the reference image from an external apparatus communicably connected with the image processing apparatus; and

a similarity calculation section for comparing the features of the input image data that are calculated by the features calculation section with the features of the reference image so as to calculate a similarity between the input image data and the reference image.

4. The image processing apparatus as set forth in claim 1, further comprising:

a storage section in which features of image data and identification information for identifying image data are stored; and

a storage process section for causing the features of the input image data that are calculated by the features calculation section and identification information for identifying the input image data to be stored in the storage section in such a manner that the features are related to the identification information.

5. The image processing apparatus as set forth in claim 1, further comprising a pattern detection process section for determining whether the partial image includes an image pattern or not,

the displaced image generation section generating the self-displaced image with respect to a partial image determined by the pattern detection process section as including an image pattern.

6. The image processing apparatus as set forth in claim 1, wherein

the displaced image generation section generates plural kinds of self-displaced images with respect to each partial image,

the matching test determination section determines whether the partial image matches each of the plural kinds of self-displaced images, and

when the partial image matches at least one of the plural kinds of self-displaced images, the detection section detects, as each of the feature points, a target pixel in the partial image or a block made of a plurality of pixels including the target pixel.

7. The image processing apparatus as set forth in claim 1, wherein the partial image extraction section extracts plural kinds of partial images by differentiating a size of an area to be extracted as a partial image.

8. The image processing apparatus as set forth in claim 7, wherein

the partial image extraction section performs a first extraction process for extracting a partial image while setting a size of an area to be extracted as the partial image to be a first size, and a second extraction process for extracting a partial image while setting a size of an area to be extracted as the partial image to be a second size larger than the first size, and

in the second extraction process, the partial image is extracted after excluding the area with the first size from the area with the second size in such a manner that the area with the first size and the area with the second size center an identical target pixel.

9. The image processing apparatus as set forth in claim 1, wherein the partial image extraction section extracts a partial image with respect to each of a plurality of color components of input image data.

10. The image processing apparatus as set forth in claim 1, further comprising:

a skew detection section for detecting an angle at which a document image included in the input image data skews; and

a skew correction section for correcting a skew of the document image in accordance with the angle detected by the skew detection section,

the input image data in which the skew of the document image is corrected being input to the partial image extraction section.

11. The image processing apparatus as set forth in claim 1, further comprising a smoothing process section for performing a smoothing process on input image data,

the feature point detection section detecting the feature points from the input image data subjected to the smoothing process.

12. An image forming apparatus, comprising an image processing apparatus as set forth in claim 1 and an image output section for forming an image corresponding to input image data on a recording material.

13. An image processing system, comprising an image processing apparatus and a server communicably connected with the image processing apparatus,

one of the image processing apparatus and the server including a feature point detection section for detecting feature points included in input image data and a features calculation section for calculating features of the input image data in accordance with relative positions of the feature points detected by the feature point detection section, or the feature point detection section and the features calculation section being divided into the image processing apparatus and the server,

the feature point detection section including:

a partial image extraction section for extracting, from the input image data, a partial image made of a plurality of pixels including a target pixel, an index for indicating busyness of the partial image being not less than a predetermined threshold value;

a displaced image generation section for generating a self-displaced image by displacing at least a part of the partial image, which has been extracted by the partial image extraction section, with other part of the partial image;

a matching test determination section for determining whether an image pattern included in the partial image matches an image pattern included in the self-displaced image or not; and

a detection section for detecting, as each of the feature points, (a) a target pixel in the partial image including the image pattern determined by the matching test determination section as matching the image pattern included in the self-displaced image, or (b) a block made of a plurality of pixels including the target pixel.

14. An image processing method, comprising:

detecting feature points included in input image data; and

calculating features of the input image data in accordance with relative positions of the feature points,

The detecting the feature points including;

extracting, from the input image data, a partial image made of a plurality of pixels including a target pixel, an index for indicating busyness of the partial image being not less than a predetermined threshold value;

generating a self-displaced image by displacing at least a part of the partial image, which has been extracted by the partial image extraction section, with other part of the partial image;

determining whether an image pattern included in the partial image matches an image pattern included in the self-displaced image; and

detecting, as each of the feature points, (a) a target pixel in the partial image including the image pattern determined in the substep (iii) as matching the image pattern included in the self-displaced image, or (b) a block made of a plurality of pixels including the target pixel.

15. A non-transitory computer-readable storage medium in which a program for causing an image processing apparatus to operate is stored, the image processing apparatus including:

a feature point detection section for detecting feature points included in input image data; and

a features calculation section for calculating features of the input image data in accordance with relative positions of the feature points detected by the feature point detection section,

the feature point detection section including;

a partial image extraction section for extracting, from the input image data, a partial image made of a plurality of pixels including a target pixel, an index for indicating busyness of the partial image being not less than a predetermined threshold value;

a displaced image generation section for generating a self-displaced image by displacing at least a part of the partial image, which has been extracted by the partial image extraction section, with other part of the partial image;

a matching test determination section for determining whether an image pattern included in the partial image matches an image pattern included in the self-displaced image or not; and

a detection section for detecting, as each of the feature points, (a) a target pixel in the partial image including the image pattern determined by the matching test determination section as matching the image pattern included in the self-displaced image, or (b) a block made of a plurality of pixels including the target pixel,

the program causing a computer to function as the feature point detection section.