Image Processing circuit and Image Processing Method

• US 20100182449A1
• Filed: 01/11/2010
• Published: 07/22/2010
• Est. Priority Date: 01/20/2009
• Status: Active Grant

• Current Assignee: MediaTek, Inc.
• Original Assignee: MStar Semiconductor Incorporated (MediaTek, Inc.)
• Inventors: Liao, Ming-Hao
• Granted Patent: US 8,421,924 B2
• Time in Patent Office: Days
• US Class Current: 348/222.100
• CPC Class Codes: H04N 5/142 Edging; Contouring
• CPC Class Codes: H04N 9/646 for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters
• CPC Class Codes: H04N 9/66 for synchronous demodulators
• CPC Class Codes: H04N 9/78 for separating the brightness signal or the chrominance signal from the colour television signal, e.g. using comb filter

Abstract

An image processing method and its associated image processing circuit for processing an image based on a sequential couleur avec memoire (SECAM) system are provided. The image includes a first pixel, a second pixel and a third pixel, which are successively arranged in a same vertical line and are respectively corresponding to a first image signal and a second image signal and a third image signal. The image processing method includes steps of calculating a chroma signal via a vertical filtering process according to the first image signal, the second image signal and the third image signal; calculating a chroma angular frequency via a frequency modulation process according to the chroma signal; and generating a chromaticity according to the chroma angular frequency.

Claims

1. An image processing method, for processing an image based on a SECAM system, the image comprising successively arranged in a vertical line a first pixel, a second pixel and a third pixel respectively corresponding to a first image signal, a second image signal and a third image signal, the image processing method comprising:

calculating a first chroma signal via a vertical filtering process according to the first image signal, the second image signal and the third image signal;

calculating a first chroma angular frequency via a frequency demodulation process according to the first chroma signal; and

generating a first chromaticity according to the first chroma angular frequency.

2. The image processing method as claimed in claim 1, wherein the step of calculating the first chroma signal comprises:

respectively multiplying the first image signal, the second image signal and the third image signal by a first multiple, a second multiple and a third multiple, a sum of the first multiple, the second multiple and the third multiple being equal to zero; and

adding up the multiplied first image signal, the multiplied second image signal and the multiplied third image signal to calculate the first chroma signal.

3. The image processing method as claimed in claim 1, further comprising:

selecting a target image signal from the first, the second and the third image signals and performing a filtering process on the target image signal to calculate a second chroma signal;

calculating a second chroma angular frequency via the frequency demodulation process according to the second chroma signal; and

obtaining a second chromaticity according to the second chroma angular frequency.

4. The image processing method as claimed in claim 3, further comprising:

adding two products from respectively multiplying the first chromaticity and the second chromaticity by a first weight and a second weight to calculate a representative chromaticity.

5. The image processing method as claimed in claim 4, before the step of adding up the two products to calculate the representative chromaticity, further comprising:

determining whether the first chroma angular frequency is greater than a threshold;

defining the first weight as being smaller than the second weight when the first chroma angular frequency is greater than the threshold; and

defining the first weight as being greater than the second weight when the first chroma angular frequency is not greater than the threshold.

6. The image processing method as claimed in claim 4, wherein the pixels successively arranged in a vertical line further comprises a fourth pixel and a fifth pixel respectively corresponding to a fourth image signal and a fifth image signal;

the fourth pixel, the first pixel, the second pixel, the third pixel and the fifth pixel are successively arranged in sequence; and

before the step of adding up the two products to calculate the representative chromaticity, the method further comprises;

calculating a third chromaticity via the vertical filtering process and the frequency demodulation process according to the fourth image signal, the first image signal and the second image signal;

calculating a fourth chromaticity via the vertical filtering process and the frequency demodulation process according to the second image signal, the third image signal and the fifth image signal;

calculating a chroma edge intensity via a chroma edge detecting process according to the third chromaticity, the first chromaticity and the fourth chromaticity; and

defining the first weight and the second weight according to the chroma edge intensity.

7. The image processing method as claimed in claim 6, wherein the step of calculating the chroma edge intensity comprises:

subtracting the first chromaticity from the third chromaticity to calculate a first chromaticity difference;

subtracting the first chromaticity from the fourth chromaticity to calculate a second chromaticity;

determining whether an absolute value of the first chromaticity difference is greater than that of the second chromaticity;

defining the absolute value of the first chromaticity as the chroma edge intensity when the absolute value of the first chromaticity difference is greater than that of the second chromaticity; and

defining the absolute value of the second chromaticity as the chroma edge intensity when the absolute value of the first chromaticity difference is not greater than that of the second chromaticity.

8. The image processing method as claimed in claim 4, before the step of calculating the representative chromaticity, further comprising:

respectively performing a notch filtering process on the first image signal, the second image signal and the third image signal to calculate a first luminosity corresponding to the first pixel, a second luminosity corresponding to the second pixel, and a third luminosity corresponding to the third pixel;

calculating a luma edge intensity via a luma edge detecting process according to the first luminosity, the second luminosity and the third luminosity; and

defining the first weight and the second weight according to the luma edge intensity.

9. The image processing method as claimed in claim 8, wherein the step of calculating the luma edge intensity comprises:

subtracting the second luminosity from the first luminosity to calculate a first luminosity difference;

subtracting the second luminosity from the third luminosity to calculate a second luminosity difference;

determining whether an absolute value of the first luminosity difference is greater than that of the second luminosity difference;

defining the absolute value of the first luminosity difference as the luma edge intensity when the absolute value of the first luminosity difference is greater than that of the second luminosity difference; and

defining the absolute value of the second luminosity difference as the luma edge intensity when the absolute value of the first luminosity difference is not greater than that of the second luminosity difference.

10. The image processing method as claimed in claim 3, further comprising:

defining a first frequency range and a second frequency range of a notch filtering process, wherein the second frequency range covers the first frequency range and is greater than the first frequency range;

performing the notch filtering process on the target image signal by using the first frequency range to calculate a fourth luminosity;

performing the notch filtering process on the target image signal by using the second frequency range to calculate a fifth luminosity; and

adding up two products from respectively multiplying the fourth chromaticity and the fifth chromaticity by a third weight and a fourth weight to calculate a representative luminosity corresponding to the target image signal.

11. An image processing circuit, for processing an image based on a SECAM system, comprising:

a receiving unit, for receiving the image comprising successively arranged in a vertical line a first pixel, a second pixel and a third pixel respectively corresponding to a first image signal, a second image signal and a third image signal;

a vertical filtering module, coupled to the receiving unit, for calculating a first chroma signal according to the first image signal, the second image signal and the third image signal;

a frequency demodulation module, coupled to the vertical filter module, for calculating a first chroma angular frequency according to the first chroma signal; and

a chroma converting unit, coupled to the frequency demodulation module, for generating a first chromaticity according to the first chroma angular frequency.

12. The image processing circuit as claimed in claim 11, wherein the vertical filter module comprises:

a first multiplication unit, for respectively multiplying the first image signal, the second image signal and the third image signal by a first multiple, a second multiple and a third multiple, a sum of the first, second and third multiples being equal to zero; and

an addition unit, coupled to the first multiplication unit, for adding up the multiplied first image signal, the multiplied second image signal and the multiplied third image signal to calculate the first chroma signal.

13. The image processing circuit as claimed in claim 11, further comprising:

a filter unit, coupled to the receiving unit, for calculating a second chroma signal according to a target image signal, which is one image signal from the first, the second and the third image signals;

wherein, the frequency demodulation module coupled to the filter unit calculates a second chroma angular frequency according to the second chroma signal, and the chroma converting unit generates a second chromaticity according to the second chroma angular frequency.

14. The image processing circuit as claimed in claim 13, further comprising:

a chroma weight module, coupled to the chroma converting unit, for adding up two products from respectively multiplying the first chromaticity and the second chromaticity by a first weight and a second weight to calculate a representative chromaticity.

15. The image processing circuit as claimed in claim 14, wherein the chroma weight module further comprises:

a first defining unit, coupled to the frequency demodulation module, for defining the first weight as being smaller than the second weight when the first chroma angular frequency is greater than a threshold and defining the first weight as being greater than the second weight when the first chroma angular frequency is not greater than the threshold.

16. The image processing circuit as claimed in claim 14, wherein the pixels successively arranged in the vertical line further comprise a fourth pixel and a fifth pixel respectively corresponding to a fourth image signal and a fifth image signal;

the fourth pixel, the first pixel, the second pixel, the third pixel and the fifth pixel are successively arranged in sequence;

the vertical filter module, the frequency demodulation module and the chroma converting unit calculate a third chromaticity according to the fourth image signal, the first image signal and the second image signal, and calculate a fourth chromaticity according to the second image signal, the third image signal and the fifth image signal; and

the image processing circuit further comprises;

a chroma edge detecting module, coupled to the chroma converting module, for calculating a chroma edge intensity according to the third chromaticity, the first chromaticity and the fourth chromaticity;

wherein, the chroma weight module comprises a second defining unit, coupled to the chroma edge detecting module, for defining the first weight and the second weight according to the chroma edge intensity.

17. The image processing circuit as claimed in claim 16, wherein the chroma edge detecting module comprises:

a first subtraction unit, for subtracting the first chromaticity from the third chromaticity to calculate a first chromaticity difference and subtracting the first chromaticity from the fourth chromaticity to calculate a second chromaticity difference; and

a first determining unit, coupled to the first subtraction unit, for determining whether an absolute value of the first chromaticity difference is greater than that of the second chromaticity difference, and defining the absolute value of the first chromaticity difference as the chroma edge intensity when the absolute value of the first chromaticity difference is greater than that of the second chromaticity difference and defining the absolute value of the second chromaticity difference as the chroma edge intensity when the absolute value of the first chromaticity difference is not greater than that of the second chromaticity difference.

18. The image processing circuit as claimed in claim 14, further comprising:

a first notch filter unit, coupled to the receiving unit, for processing the first image signal, the second image signal and the third image signal to respectively calculate a first luminosity corresponding to the first pixel, a second luminosity corresponding to the second pixel and a third luminosity corresponding to the third pixel; and

a luma edge detecting module, coupled to the first notch filter unit, for calculating a luma edge intensity according to the first luminosity, the second luminosity and the third luminosity;

wherein, the chroma weight module comprises a third defining unit, coupled to the luma edge detecting module, for defining the first weight and the second weight according to the luma edge intensity.

19. The image processing circuit as claimed in claim 18, wherein the luma edge detecting module comprises:

a second subtraction unit, for subtracting the second luminosity from the first luminosity to calculate a first luminosity difference and subtracting the second luminosity from the third luminosity to calculate a second luminosity difference; and

a second determining unit, coupled to the first subtraction unit, for determining whether an absolute value of the first luminosity difference is greater than that of the second luminosity difference, and defining the absolute value of the first luminosity difference as the luma edge intensity when the absolute value of the first luminosity difference is greater than that of the second luminosity difference and defining the absolute value of the second luminosity difference as the luma edge intensity when the absolute value of the first luminosity difference is not greater than that of the second luminosity difference.

20. The image processing circuit as claimed in claim 13, further comprising:

a second notch filter unit, coupled to the receiving unit, for processing the target image signal by using a first frequency range to calculate a fourth luminosity;

a third notch filter unit, coupled to the receiving unit, for processing the target image signal by using a second frequency range to calculate a fifth luminosity, wherein the second filtering frequency range covers the first filtering frequency range and is greater than the first filtering frequency range; and

a luma weight module, coupled to the second notch filter unit and the third notch filter unit, for adding up two products from respectively multiplying the fourth luminosity and the fifth luminosity by a third weight and a fourth weight to calculate a representative luminosity corresponding to the target image signal.