Digital color image pre-processing

• US 7,102,669 B2
• Filed: 04/02/2002
• Issued: 09/05/2006
• Est. Priority Date: 04/02/2002
• Status: Expired due to Term

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Skow, Michael
• Primary Examiner(s): Ometz, David
• Assistant Examiner(s): Tran, Nhan
• Application Number:
  US10/115,176
• Publication Number:
  US 20030184659A1
• Time in Patent Office: 1,617 Days
• Field of Search: 348/221, 348/222, 348/223, 348/229, 348/241, 348/273, 348/280, 348/221.1, 348/222.1, 348/223.1, 348/229.1, 348/254
• US Class Current: 348/222.1
• CPC Class Codes: H04N 2209/046 Colour interpolation to calculate the missing colour values
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values

Abstract

In one embodiment, the invention involves a method for processing an image. A sensor output is provided. An automatic gain control of the sensor output is performed to generate a first output. An automatic white balance correction to the first output is performed to generate a second output. A gamma correction of the second output is performed to generate a third output. A color interpolation is performed to the third output to generate a fourth output. A low-pass spatial filtration of the fourth output is performed to generate a fifth output. A color saturation and correction of the fifth output is performed to generate a sixth output, and a high-pass spatial filtration of the sixth output is performed to generate an image output.

Claims

1. A method for processing an image, comprising:

providing a sensor output;

performing an automatic gain control of the sensor output to generate a first output,

wherein the automatic gain control is applied in a digital domain, including

performing an expansion of a histogram to fill a dynamic range;

performing an automatic white balance correction to the first output to generate a second output;

performing a gamma correction of the second output to generate a third output, wherein

the gamma correction performs a variable gamma correction to increase a

dynamic range of an image included in the second output;

performing a color interpolation to the third output to generate a fourth output;

performing a low-pass spatial filtration of the fourth output to generate a fifth output,

wherein the low-pass spatial filtration is for eliminating a fixed pattern noise in a flat field;

performing a color saturation and correction of the fifth output to generate a sixth output; and

performing a high-pass spatial filtration of the sixth output to generate an image output.

2. The method of claim 1, wherein the automatic white balance correction comprises calculating a gray world model ratio of a set of colors in a pattern and applying a multiplier to each color.

3. The method of claim 1, wherein the gamma correction is performed in gray space.

4. The method of claim 1, wherein the color interpolation comprises performing a three-by-three edge enhanced demosaic of a raw Bayer signal to an RGB signal.

5. The method of claim 1, wherein the low-pass spatial filtration comprises performing a low-pass spatial filter on each of a plurality of color planes.

6. The method of claim 1, wherein the color saturation and correction comprises manipulating color ratios of a plurality of color planes within each of a plurality of pixels.

7. The method of claim 1, wherein the high-pass spatial filtration comprises enhancing a spatial edge.

8. An imaging device configured to implement the method of claim 1.

9. An application specific integrated circuit configured to implement the method of claim 1.