Image processing apparatus and image processing method

• US 7,262,884 B2
• Filed: 11/22/2002
• Issued: 08/28/2007
• Est. Priority Date: 11/22/2002
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation), Toshiba Tec Corporation (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation), Toshiba Tec Corporation (Toshiba Corporation)
• Inventors: Kawakami, Haruko
• Primary Examiner(s): Lamb; Twyler
• Assistant Examiner(s): Vo; Quang N.
• Application Number:
  US10/301,797
• Publication Number:
  US 20040252343A1
• Time in Patent Office: 1,740 Days
• Field of Search: 358/1.9, 358/2.1, 358462-466, 358/453, 358/426.13, 382245-246, 382173-176, 382254-255
• US Class Current: 358/2.1
• CPC Class Codes: G06V 30/413 Classification of content, e.g. text, photographs or tables
• CPC Class Codes: H04N 1/40062 Discrimination between different image types, e.g. two-tone, continuous tone
• CPC Class Codes: H04N 1/56 Processing of colour picture signals H04N1/52 takes precedence

Abstract

A white background determination section performs a white background determination on the basis of a white threshold calculated by a white threshold calculation section and an area size selected by an area size determination section. A character discrimination section executes character recognition such that a condition for character discrimination is relaxed when the white background determination section determines that a pixel of interest belongs to a white background, and the condition for character discrimination is made stricter in other cases.

Claims

1. An image processing apparatus comprising:

a calculation section that calculates a value used to determine an attribute of an area on the basis of an image signal;

an area size determination section that determines an area size on the basis of a predetermined condition; and

an area attribute determination section that determines an attribute of a pixel of interest in the image signal, on the basis of the area size determined by the area size determination section and the value that is calculated by the calculation section and is used to determine the attribute of the area,

wherein the area attribute determination section finds, with use of a white threshold calculated by the calculation section, an occupation ratio of white pixels in an area of interest of the area size determined by the area size determination section,

wherein when the occupation ratio found by the area attribute determination section is greater than a predetermined first occupation ratio threshold, the area attribute determination section determines the pixel of interest to be a pixel in a white background area, and

wherein the area attribute determination section finds a difference value in a main scan direction and a difference value in a sub-scan direction in the area of interest of the area size determined by the area size determination section, counts a number of locations where the difference value is greater than a preset first threshold, finds the count value both in the main scan direction and sub-scan direction, compares each count value with a preset second threshold, and, when each count value is greater than the second threshold, uses a second occupation ratio threshold that is greater than the first occupation ratio threshold.

2. An image processing apparatus comprising:

a calculation section that calculates a value used to determine an attribute of an area on the basis of an image signal;

an area size determination section that determines an area size on the basis of a predetermined condition;

an area attribute determination section that determines an attribute of a pixel of interest in the image signal, on the basis of the area size determined by the area size determination section and the value that is calculated by the calculation section and is used to determine the attribute of the area; and

an achromatic color determination section that determines, based on the image signal, whether an area of interest is composed of only an achromatic character, and a character discrimination section that performs character discrimination of the pixel of interest on the basis of a determination result of the area attribute determination section and a determination result of the achromatic color determination section,

wherein the achromatic color determination section calculates color difference equivalent values C1cen and C2cen of a pixel with a maximum luminance Dmax of an original document, and determines that that the area of interest is composed of only an achromatic character when the following formula is satisfied;

((C1−

C1cen)/R1)²+((C2−

C2cen)/R2)²≦

1

where R1 and R2 designate a major axis and a minor axis of an oval representing an achromatic area.