Method and apparatus for digital camera real-time image correction in preview mode

• US 6,778,216 B1
• Filed: 03/24/2000
• Issued: 08/17/2004
• Est. Priority Date: 03/25/1999
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Lin, Gene Chun-Yin
• Primary Examiner(s): HO, TUAN V
• Application Number:
  US09/534,805
• Time in Patent Office: 1,607 Days
• Field of Search: 348/207.99, 348/231.99, 348/231.3, 348/231.6, 348/222.1, 348/223.1, 348/229.1, 348/254, 348/333.01, 348/333.11, 348/333.12, 348/350, 348/220.1, 382/124, 382/167, 235/470
• US Class Current: 348/333.11
• CPC Class Codes: H04N 1/0044 for image preview or review, e.g. to help the user position a sheet
• CPC Class Codes: H04N 1/6011 with simulation on a subsidiary picture reproducer H04N1/622 takes precedence; matching two or more picture reproducers H04N1/6052
• CPC Class Codes: H04N 23/63 by using electronic viewfinders
• CPC Class Codes: H04N 23/667 Camera operation mode switching, e.g. between still and video, sport and normal or high- and low-resolution modes
• CPC Class Codes: H04N 23/841 to modify gamut
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements

Abstract

A method for previewing an image in a camera prior to output. The method includes steps of gathering image data, storing the image data, calculating display parameters using the stored image data, storing the display parameters in a look-up table; and applying the display parameters in the look-up table to at least a portion of the image data to produce preview image data. The display parameters can be quickly calculated using a digital signal processor to achieve real-time image previewing. The parameters used in an embodiment camera are vertical down sampling (51) white balance and gain control (52), horizontal up/down sampling (53), and color space conversion and gamma correction (55). The resulting preview processed image may be stored in memory via an interface (56) and viewed via a preview display. Once calculated using a preview algorithm run on a digital signal processor, these parameters can be combined in one or more look-up tables that can be updated by the digital signal processor as imaging conditions demand.

Claims

1. A method for previewing an image in a camera prior to output, comprising the steps of:

a) gathering image data;

b) storing said image data;

c) calculating display parameters using said stored image data;

d) storing said display parameters in a look-up table;

e) applying said display parameters in said look-up table to at least a portion of said image data to produce preview image data.

2. The method of claim 1, wherein said steps of calculating display parameters and storing said display parameters include the steps of:

a) calculating a white balance adjustment and a gain control adjustment;

b) combining said white balance and gain control adjustments; and

c) storing said combined white balance adjustment and gain control adjustment in said look-up table.

3. The method of claim 1, wherein said steps of calculating display parameters and storing said display parameters include the steps of:

a) calculating a gamma correction and performing color space conversion;

b) combining said gamma correction and color space conversion; and

c) storing said combined gamma correction and color space conversion in said look-up table.

4. The method of claim 3, further comprising the steps of:

a) calculating a white balance adjustment; and

b) storing said white balance adjustment with said combined gamma correction and color space conversion in said look-up table.

5. The method of claim 1, wherein said step of storing said image data includes the step of loading image data into a random access memory and said step of calculating includes the steps of:

using a digital signal processor to access said random access memory; and

using said digital signal processor to determine said display parameters using said image data in said random access memory in a preview algorithm.

6. The method of claim 1, wherein said steps are performed in real time.

7. A method for previewing an image in a digital camera prior to output, comprising the steps of:

a) gathering image data;

b) digitizing said image data;

c) storing said digitized image data;

d) sampling a portion of said digitized image data;

e) calculating white balance adjustment and gain control parameters using said stored digitized image data;

f) storing said white balance adjustment and gain control parameters in a look-up table; and

g) applying said white balance adjustment and gain control parameters in said look-up table to said portion of said digitized image data to produce preview image data.

8. The method of claim 7, further comprising the steps of:

calculating a gamma correction and performing color space conversion;

storing said gamma correction and said color space conversion in said look-up table; and

applying said gamma correction and said color space conversion in said look-up table to said portion of said image data to produce preview image data.

9. The method of claim 7, wherein said step of sampling comprises alternately loading said digitized image data into two line buffers and programmably selecting data from said line buffers.

10. A digital camera, comprising:

a) an image-gathering device;

b) a preview engine coupled to said image-gathering device, wherein said preview engine includes a look-up table and a color interpolator;

c) a display coupled to said preview engine;

d) a storage device coupled to said image-gathering device; and

e) a processor coupled to said look-up table and to said storage device.

11. A digital camera, comprising:

a) an image-gathering device;

b) a preview engine coupled to said image-gathering device, wherein said preview engine includes a look-up table and a sampling circuit;

c) a display coupled to said preview engine;

d) a storage device coupled to said image-gathering device; and

e) a processor coupled to said look-up table and to said storage device.

12. The digital camera of claim 11, wherein said sampling circuit comprises a circuit operable to sample image data in a predetermined direction, said circuit further comprising:

a line buffer coupled to said storage device and operable to receive and store data from said storage device;

a circuit for selecting data from said line buffer, said circuit coupled to said display.

13. The digital camera of claim 11, wherein said sampling circuit comprises a circuit operable to sample data in a predetermined direction, said circuit further comprising:

two line buffers coupled to said storage device and operable to receive and store data from said storage device;

a circuit for selecting blocks of data from said two line buffers, said circuit coupled to said display.