Color interpolation method

• US 20050117040A1
• Filed: 11/18/2004
• Published: 06/02/2005
• Est. Priority Date: 11/28/2003
• Status: Active Grant

• Current Assignee: Megachips Corporation
• Original Assignee: Megachips LSI Solutions Incorporated (Megachips Corporation)
• Inventors: Matsutani, Takashi
• Granted Patent: US 7,499,089 B2
• Time in Patent Office: Days
• US Class Current: 348/272
• CPC Class Codes: H04N 2209/046 Colour interpolation to calculate the missing colour values
• 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

Abstract

A sensor such as a CCD image pickup device is equipped with a color filter of RGB Bayer array. An image is read from such a sensor (S1) and inputted to a color interpolation device as raw data (S2). The color interpolation device calculates additional values DH and DV of differential absolute values of pixel values in a horizontal direction and a vertical direction by using pixels of all colors in a peripheral area of a specified pixel (S3 and S4). The additional values DH and DV are compared with each other (S5) and when it is judged that there is a tendency of pixel drift in the horizontal direction or the vertical direction, S6 is executed. In S6, when a correlation in the vertical direction is strong, an interpolation using vertical adjacent pixels is performed and when a correlation in the horizontal direction is strong, an interpolation using horizontal adjacent pixels is performed. By this method, it is possible to improve the accuracy of color interpolation.

Claims

1. A color interpolation method comprising:

a first step of inputting pixel data of Bayer array in a predetermined color space;

a second step of setting a predetermined area around a specified pixel and calculating a pixel-value change evaluation value in a horizontal direction (hereinafter, referred to as a horizontal evaluation value) and a pixel-value change evaluation value in a vertical direction (hereinafter, referred to as a vertical evaluation value) by using pixel data of all color components in said predetermined area;

a third step of comparing said horizontal evaluation value and said vertical evaluation value; and

a fourth step of performing pixel interpolation using pixel values in said vertical direction about said specified pixel when it is judged from a comparison of said third step that a pixel value change in said horizontal direction is larger or performing pixel interpolation using pixel values in said horizontal direction about said specified pixel when it is judged from a comparison of said third step that a pixel value change in said vertical direction is larger.

2. The color interpolation method according to claim 1, wherein

said horizontal evaluation value is a value obtained by adding up all differential absolute values of pixel values of the same color pixel data which are adjacent to one another in said horizontal direction in said predetermined area, and said vertical evaluation value is a value obtained by adding up all differential absolute values of pixel values of the same color pixel data which are adjacent to one another in said vertical direction in said predetermined area.

3. The color interpolation method according to claim 1, wherein

said third step includes the step of

judging whether the difference between said horizontal evaluation value and said vertical evaluation value exceeds a predetermined threshold value or not, and

said fourth step is performed only when said difference between said horizontal evaluation value and said vertical evaluation value exceeds said predetermined threshold value in said third step.

4. The color interpolation method according to claim 1, wherein

assuming that a color which is arranged in a checkered pattern in said Bayer array is a first color component, said specified pixel is a second color component other than said first color component, and

said fourth step includes the step of

performing pixel interpolation of said first color component on said specified pixel by using pixel values of two pixel data of said first color component which are vertically adjacent to said specified pixel when it is judged that said pixel value change in said horizontal direction is larger and performing pixel interpolation of said first color component on said specified pixel by using pixel values of two pixel data of said first color component which are horizontally adjacent to said specified pixel when it is judged that said pixel value change in said vertical direction is larger.

5. The color interpolation method according to claim 4, wherein

said predetermined color space is an RGB color space and said first color component is G component.

6. The color interpolation method according to claim 1, wherein

said predetermined area is a pixel area of 5×

5 around said specified pixel.