Image processing method and apparatus

• US 6,370,278 B1
• Filed: 01/19/1999
• Issued: 04/09/2002
• Est. Priority Date: 01/16/1998
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Waguri, Shinichi
• Primary Examiner(s): ROGERS, SCOTT A
• Application Number:
  US09/233,102
• Time in Patent Office: 1,176 Days
• Field of Search: 382/266, 382/254, 382/162, 382/167, 358/530, 358/532, 358/500, 358/529, 358/447
• US Class Current: 382/266
• CPC Class Codes: H04N 1/40012 Conversion of colour to monochrome

Abstract

A color-to-monochrome image conversion technique is disclosed. After the color image is converted to a monochrome input image and a plurality of primary-color input images, boundary information is extracted from the plurality of primary-color input images. The boundary information discriminates between different colors with the same lightness in the color image. Thereafter, the boundary information is superimposed as a binary image on the monochrome input image to produce the monochrome image. Therefore, a boundary between different colors with the same lightness can be easily imagined and be visibly displayed.

Claims

1. An image processing method for converting a color image into a monochrome image, comprising the steps of:

a) converting the color image to a monochrome input image and a plurality of primary-color input images;

b) extracting boundary information from the plurality of primary-color input images, wherein the boundary information discriminates between different colors with the same lightness in the color image; and

c) superimposing the boundary information as a binary image on the monochrome input image to produce the monochrome image.

2. The image processing method according to claim 1, wherein the step b) comprises the steps of:

b-1) detecting an edge of each of the primary-color input images to produce edge detection images of the primary-color input images; and

b-2) combining the edge detection images to produce a combined edge detection image as the boundary information; and

the step c) comprises the step of

c-1) superimposing the combined edge detection image on the monochrome input image to produce the monochrome image where a boundary discriminates between different colors with the same lightness.

3. The image processing method according to claim 2, wherein the step c-1) comprises the step of removing the combined edge detection image from the monochrome input image to produce the monochrome image.

4. The image processing method according to claim 2, wherein the step c-1) comprises the step of:

detecting an edge of the monochrome input image to produce a monochrome edge detection image;

extracting the boundary by exclusively combining the combined edge detection image with the monochrome edge detection image; and

removing the boundary from the monochrome input image to produce the monochrome image.

5. The image processing method according to claim 2, wherein the step c-1) comprises the steps of:

converting the monochrome input image into a binary input image; and

removing the combined edge detection image from the binary input image to produce the monochrome image.

6. The image processing method according to claim 2, wherein the step c-1) comprises the step of:

detecting an edge of the monochrome input image to produce a monochrome edge detection image;

converting the monochrome input image into a binary input image;

extracting the boundary by exclusively combining the combined edge detection image with the monochrome edge detection image; and

removing the boundary from the binary input image to produce the monochrome image.

20. The computer-implemented method according to claim 1, wherein the step b) comprises the steps of:

b-1) detecting an edge of each of the primary-color input images to produce edge detection images of the primary-color input images; and

b-2) combining the edge detection images to produce a combined edge detection image as the boundary information, wherein in the step c), the combined edge detection image is superimposed on the monochrome input image to produce the monochrome image where a boundary discriminates between different colors with the same lightness.

7. An image processing apparatus for converting a color image into a monochrome image, comprising:

a first converter for converting the color image to a monochrome input image and a plurality of primary-color input images;

a first extractor for extracting boundary information from the plurality of primary-color input images, wherein the boundary information discriminates between different colors with the same lightness in the color image; and

a processor for superimposing the boundary information as a binary image on the monochrome input image to produce the monochrome image.

8. The image processing apparatus according to claim 7, wherein the first extractor comprises:

a first edge detector for detecting an edge of each of the primary-color input images to produce edge detection images of the primary-color input images; and

a first combiner for combining the edge detection images to produce a combined edge detection image,

wherein the processor superimposes the combined edge detection image on the monochrome input image to produce the monochrome image where a boundary discriminates between different colors with the same lightness.

9. The image processing apparatus according to claim 8, wherein the processor removes the combined edge detection image from the monochrome input image to produce the monochrome image.

10. The image processing apparatus according to claim 8, wherein the processor comprises:

a second edge detector for detecting an edge of the monochrome input image to produce a monochrome edge detection image;

a second extractor for extracting the boundary by exclusively combining the combined edge detection image with the monochrome edge detection image; and

an exclusive combiner for removing the boundary from the monochrome input image to produce the monochrome image.

11. The image processing apparatus according to claim 8, wherein the processor comprises:

a second converter for converting the monochrome input image into a binary input image; and

an exclusive combiner for removing the combined edge detection image from the binary input image to produce the monochrome image.

12. The image processing apparatus according to claim 8, wherein the processor comprises:

a second edge detector for detecting an edge of the monochrome input image to produce a monochrome edge detection image;

a second converter for converting the monochrome input image into a binary input image;

a second extractor for extracting the boundary by exclusively combining the combined edge detection image with the monochrome edge detection image; and

an exclusive combiner for removing the boundary from the binary input image to produce the monochrome image.

13. A facsimile apparatus for transmitting a black-and-white image produced from a color image, comprising:

a first converter for converting the color image to a monochrome input image and a plurality of primary-color input images;

a first extractor for extracting boundary information from the plurality of primary-color input images, wherein the boundary information discriminates between different colors with the same lightness in the color image;

a processor for superimposing the boundary information as a binary image on the monochrome input image to produce the black-and-white image; and

a facsimile transmitter for transmitting the black-and-white image to an opposite party.

14. The facsimile apparatus according to claim 13, wherein the first extractor comprises:

a first edge detector for detecting an edge of each of the primary-color input images to produce edge detection images of the primary-color input images; and

a first combiner for combining the edge detection images to produce a combined edge detection image,

wherein the processor superimposes the combined edge detection image on the monochrome input image to produce the black-and-white image where a boundary discriminates between different colors with the same lightness.

15. The facsimile apparatus according to claim 13, wherein the processor removes the combined edge detection image from the monochrome input image to produce the black-and-white image.

16. The facsimile apparatus according to claim 13, wherein the processor comprises:

a second edge detector for detecting an edge of the monochrome input image to produce a monochrome edge detection image;

a second extractor for extracting the boundary by exclusively combining the combined edge detection image with the monochrome edge detection image; and

an exclusive combiner for removing the boundary from the monochrome input image to produce the black-and-white image.

17. The facsimile apparatus according to claim 13, wherein the processor comprises:

a second converter for converting the monochrome input image into a binary input image; and

an exclusive combiner for removing the combined edge detection image from the binary input image to produce the black-and-white image.

18. The facsimile apparatus according to claim 13, wherein the processor comprises:

a second edge detector for detecting an edge of the monochrome input image to produce a monochrome edge detection image;

a second converter for converting the monochrome input image into a binary input image;

a second extractor for extracting the boundary by exclusively combining the combined edge detection image with the monochrome edge detection image; and

an exclusive combiner for removing the boundary from the binary input image to produce the black-and-white image.

19. A computer-implemented method for converting a color image into a monochrome image, comprising the steps of:

a) converting the color image to a monochrome input image and a plurality of primary-color input images;

b) extracting boundary information from the plurality of primary-color input images, wherein the boundary information discriminates between different colors with the same lightness in the color image; and

c) superimposing the boundary information as a binary image on the monochrome input image to produce the monochrome image.