Processing for accurate reproduction of symbols and other high-frequency areas in a color image

• US 6,999,619 B2
• Filed: 07/11/2001
• Issued: 02/14/2006
• Est. Priority Date: 07/12/2000
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Toda, Yukari
• Primary Examiner(s): Mehta, Bhavesh M.
• Assistant Examiner(s): Alavi, Amir
• Application Number:
  US09/902,172
• Publication Number:
  US 20020037102A1
• Time in Patent Office: 1,679 Days
• Field of Search: 382/162, 382/165, 382/168, 382/172, 382/199, 382/264, 382/272, 358/3.06, 358/3.21, 358/466, 358/500
• US Class Current: 382/172
• CPC Class Codes: G06T 2207/10008 from scanner, fax or copier
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 2207/30176 Document
• CPC Class Codes: G06T 7/11 Region-based segmentation
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/162 Quantising the image signal
• CPC Class Codes: G06V 30/413 Classification of content, e.g. text, photographs or tables
• CPC Class Codes: H04N 1/403 Discrimination between the two tones in the picture signal of a two-tone original
• CPC Class Codes: H04N 1/41 Bandwidth or redundancy reduction by scanning H04N1/17 ; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00
• CPC Class Codes: H04N 19/12 Selection from among a plurality of transforms or standards, e.g. selection between discrete cosine transform [DCT] and sub-band transform or selection between H.263 and H.264
• CPC Class Codes: H04N 19/136 Incoming video signal characteristics or properties
• CPC Class Codes: H04N 19/17 the unit being an image region, e.g. an object
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/90 using coding techniques not provided for in groups H04N19/10-H04N19/85, e.g. fractals

Abstract

In image processing for accurate reproduction of the color of a high-frequency area, a histogram is calculated that is consonant with an input image, and, based on the histogram, there is calculated a binary threshold value with which a predetermined area in the input image is blurred. The input image is binarized using the binary threshold value, and the color of the predetermined area of the input image is calculated based on the results obtained in the binarization.

Claims

1. An image processing apparatus comprising:

histogram calculation means for calculating a histogram that is consonant with an input image;

binary threshold value calculation means for calculating a binary threshold value, based on the histogram, with which a predetermined area in the input image is blurred;

binarization means for binarizing the input image using the binary threshold value; and

calculation means for calculating the color of the predetermined area of the input image based on the results obtained by said binarization means.

2. An image processing apparatus according to claim 1, wherein, by referring to a binary image obtained by said binarizing means, said calculation means calculates the average value of portions in the input image that correspond to black portions of the binary image, and calculates the color of a predetermined area of the input image based on the average value.

3. An image processing apparatus according to claim 1, wherein, by referring to a binary image obtained by said binarizing means, said calculation means calculates a histogram for portions in the input image that correspond to black portions of the binary image, and calculates the color of a predetermined area of the input image based on the histogram.

4. An image processing apparatus according to claim 1, wherein said binarizing means further includes inversion means for inverting the binarized results.

5. An image processing apparatus according to claim 1, wherein the image in the predetermined area is a symbol image.

6. An image processing method comprising:

a histogram calculation step of calculating a histogram that is consonant with an input image;

a binary threshold value calculation step of calculating a binary threshold value, based on the histogram, with which a predetermined area in the input image is blurred;

a binarization step of binarizing the input image using the binary threshold value; and

a calculation step of calculating the color of the predetermined area of the input image based on the results obtained at said binarization step.

7. An image processing method according to claim 6, wherein, by referring to a binary image obtained at said binarizing step, at said calculation step, the average value of portions in the input image that correspond to black portions of the binary image is calculated, and the color of a predetermined area of the input image is calculated based on the average value.

8. An image processing method according to claim 6, wherein, by referring to a binary image obtained at said binarizing step, at said calculation step, a histogram for portions in the input image that correspond to black portions of the binary image is calculated, and the color of a predetermined area of the input image is calculated based on the histogram.

9. An image processing method according to claim 6, wherein said binarizing step further includes an inversion step of inverting the binarized results.

10. An image processing method according to claim 6, wherein the image in the predetermined area is a symbol image.

11. A computer-readable storage medium on which stored is a program comprising:

a code for calculating a histogram that is consonant with an input image;

a code for calculating a binary threshold value, based on the histogram, with which a predetermined area in the input image is blurred;

a code for binarizing the input image using the binary threshold value; and

a code for calculating the color of the predetermined area of the input image based on the results obtained at said binarization.