Method of adjusting digital camera image processing parameters
A method for adjusting predetermined ISO-dependent image processing parameters for images captured by a digital camera includes measuring the exposure deviation in exposure units from an optimal exposure as determined by the camera during an image capture process, deriving an estimated camera sensitivity from the exposure deviation, and adjusting the ISO-dependent image processing parameters for images captured by the camera as a function of the derived estimated camera sensitivity.
1. A method for adjusting image processing parameters for an image captured by a digital camera comprising:
for every image captured by the camera;
automatically generating image statistics for the entire captured image after the image has been captured;
generating an estimated camera sensitivity as a function of a preset ISO setting in the camera and the image statistics of the captured image;
automatically adjusting ISO-dependent image processing parameters for the captured image captured by the camera as a function of the generated estimated camera sensitivity without employing data from additionally captured images; and
automatically processing the captured image using the adjusted parameters to create an adjusted image.
2. The method of claim 1 wherein generating the estimated camera sensitivity using actual image statistics comprises generating the estimated camera sensitivity as a function of the average, median, or maximum value of the image and an intensity value predetermined for the ISO setting.
3. The method of claim 1 wherein generating the estimated camera sensitivity using actual image statistics comprises generating the estimated camera sensitivity as a function of the combination of the average, median, and maximum image values.
4. The method of claim 1 wherein generating an estimated camera sensitivity comprises generating the estimated camera sensitivity as a function of a reference histogram obtained in calibration and a histogram of the actual image.
5. The method of claim 4 wherein generating the estimated camera sensitivity as a function of a reference histogram obtained in calibration and a histogram of the actual image comprises generating the estimated camera sensitivity as a weighted function of a reference histogram obtained in calibration and a histogram of the actual image.
6. The method of claim 5 , wherein the weighted function employs predetermined weights.
7. The method of claim 6 wherein the predetermined weights are updated as a function of image statistics.
8. The method of claim 7 wherein updating the weights as a function of image statistics includes calculating the weights as a function of the difference between the reference histogram obtained in calibration and a histogram of the actual image.
9. The method of claim 5 , wherein the weighted function employs different weights for different histogram levels.
10. The method of claim 5 , wherein the weighted function employs weights adaptively determined from image statistics.
11. The method of claim 5 , further including rejecting outlying measurements by setting their corresponding weights to zero.
12. The method of claim 1 wherein generating an estimated camera sensitivity comprises generating an estimated camera sensitivity using actual image statistics from at least one or more image region of interest.
13. The method of claim 12 wherein the at least one region of interest is at least one region that is in focus.
14. The method of claim 12 wherein the at least one region of interest is at least one region determined via object detection/pattern recognition.
15. The method of claim 12 wherein the image is divided into regular blocks, the camera sensitivity is estimated in each of the blocks, and a weighted average is made of the individual camera sensitivities determined in each of the blocks.