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

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;
• a rotated image generating section for generating a self-rotated image by rotating the partial image by a predetermined angle;
• a matching test determination section for determining whether an image pattern included in the partial image matches an image pattern included in the self-rotated image or not, when the partial image is caused to overlap the self-rotated image;
• 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-rotated image, or (b) a block made of a plurality of pixels including the target pixel.

An image processing method, comprising the steps of:

• (I) detecting feature points included in input image data;
• and
• (II) calculating features of the input image data in accordance with relative positions of the feature points detected in the step (I),
• the step (I) including the substeps of:
• (i) extracting, from the input image data, a partial image made of a plurality of pixels including a target pixel;
• (ii) generating a self-rotated image by rotating the partial image by a predetermined angle;
• (iii) determining whether an image pattern included in the partial image matches an image pattern included in the self-rotated image or not, when the partial image is caused to overlap the self-rotated image;
• and
• (iv) 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-rotated image, or (b) a block made of a plurality of pixels including the target pixel.

A 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;
• a rotated image generating section for generating a self-rotated image by rotating the partial image by a predetermined angle;
• a matching test determination section for determining whether an image pattern included in the partial image matches an image pattern included in the self-rotated image or not, when the partial image is caused to overlap the self-rotated image;
• 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-rotated 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.