Circuit and method for contour enhancement

• US 20040119859A1
• Filed: 07/25/2003
• Published: 06/24/2004
• Est. Priority Date: 07/25/2002
• Status: Active Grant

• Current Assignee: Socionext Inc.
• Original Assignee: Fujitsu Limited
• Inventors: Nishio, Shigeru, Daiku, Hiroshi, Kokubo, Asao
• Granted Patent: US 7,352,397 B2
• Time in Patent Office: Days
• US Class Current: 348/252
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements
• CPC Class Codes: H04N 5/142 Edging; Contouring
• CPC Class Codes: H04N 5/208 for compensating for attenuation of high frequency components, e.g. crispening, aperture distortion correction

Abstract

A semiconductor integrated circuit includes a differential calculating unit which obtains a differential between a value of a pixel of interest and values of surrounding pixels contained in an image signal supplied from an image sensor, a dead-zone generating unit which defines a predetermined range of pixel values, and a comparison unit which checks whether the differential falls outside the predetermined range, wherein contour enhancement is applied to the pixel of interest in response to a determination by the comparison unit that the differential falls outside the predetermined range.

Claims

1. A semiconductor integrated circuit, comprising:

a differential calculating unit which obtains a differential between a value of a pixel of interest and values of surrounding pixels contained in an image signal supplied from an image sensor;

a dead-zone generating unit which defines a predetermined range of pixel values; and

a comparison unit which checks whether the differential falls outside the predetermined range,

wherein contour enhancement is applied to the pixel of interest in response to a determination by the comparison unit that the differential falls outside the predetermined range.

2. The semiconductor integrated circuit as claimed in claim 1, further comprising a enhancement value generating unit which obtains an enhancement value based on differentials between the value of the pixel of interest and the values of the surrounding pixels, said enhancement value generating unit adding the enhancement value to the value of the pixel of interest in response to the determination by the comparison unit that the differential falls outside the predetermined range.

3. The semiconductor integrated circuit as claimed in claim 1, wherein said differential calculating unit obtains the differential by using only a green-color component among a plurality of color components of the image signal.

4. The semiconductor integrated circuit as claimed in claim 1, wherein said differential calculating unit obtains the differential by using only a green-color component among a plurality of color components of the image signal, and said enhancement value generating unit obtains the enhancement value by using only the green-color component.

5. The semiconductor integrated circuit as claimed in claim 1, further comprising a luminance signal generating unit which obtains a luminance component from a plurality of color components of the image signal, and said differential calculating unit obtains the differential by using only the luminance component.

6. The semiconductor integrated circuit as claimed in claim 1, further comprising a luminance signal generating unit which obtains a luminance component from a plurality of color components of the image signal, wherein said differential calculating unit obtains the differential by using only the luminance component, and said enhancement value generating unit obtains the enhancement value by using only the luminance component.

7. The semiconductor integrated circuit as claimed in claim 1, wherein said differential calculating unit obtains a difference between the value of the pixel of interest and an average of the values of the surrounding pixels as said differential.

8. The semiconductor integrated circuit as claimed in claim 1, wherein said differential calculating unit obtains a difference between the value of the pixel of interest and a value of an adjacent pixel with respect to each of four neighboring pixels as said differential, and the comparison unit checks whether the differential falls within the predetermined range with respect to each of the four neighboring pixels.

9. The semiconductor integrated circuit as claimed in claim 8, wherein said enhancement value generating unit selects a differential having a largest absolute value among each said differential corresponding to the four neighboring pixels, and performs said contour enhancement in response to size of the differential having the largest absolute value.

10. The semiconductor integrated circuit as claimed in claim 9, wherein said contour enhancement is not performed if an absolute value of a largest one of each said differential corresponding to the four neighboring pixels is identical to an absolute value of a smallest one of each said differential corresponding to the four neighboring pixels.

11. A method of enhancing contours, comprising the steps of:

obtaining a differential between a value of a pixel of interest and values of surrounding pixels contained in an image signal supplied from an image sensor;

defining a predetermined range of pixel values;

checking whether the differential falls outside the predetermined range; and

applying contour enhancement to the pixel of interest in response to a determination that the differential falls outside the predetermined range.