Incorporating pixel replacement for negative values arising in dark frame subtraction
AssigneeHewlett-Packard Development Company, L.P.
InventorDaniel M. Bloom
Life of this patent
Estimating the term…
Abstract
An apparatus and method of processing images in a digital camera and improving the quality of images produced by camera processing software. In low-light digital camera photography, a dark frame image is subtracted from an original picture image to form a resulting image. The resulting image formed from the dark frame subtraction is evaluated for negative and invalid pixel values. Each negative and invalid pixel value is replaced using a pixel replacement algorithm with appropriate positive values.
Claims24
A method for improving the quality of low-light images of a digital camera, said method comprising the steps of:
- receiving a low-light image and a dark frame, said low-light image and said dark frame having respective pixels therein, each said pixel having a respective pixel value associated therewith;
- subtracting respective pixel values of said dark frame from the corresponding pixel value of said low-light image, forming a resulting image therefrom having respective pixel values associated therewith;
- analyzing the respective pixel values of said resulting image for pixel values below a pixel threshold value, pixel values below said pixel threshold value constituting illegal pixels and pixel value at and above said pixel value threshold constituting legal pixel values;
- replacing respective illegal pixel values with respective legal pixel values according to a pixel replacement algorithm, forming a corrected resulting image therefrom;
- and
- outputting said corrected resulting image.
A method for improving the quality of low-light images of a digital camera, said method comprising the steps of:
- receiving a low-light image and a dark frame, said low-light image and said dark frame having respective pixels therein, each said pixel having a respective pixel value associated therewith, wherein said dark frame contains pixel locations of pixels corresponding to significant dark current in said low-light image;
- marking said dark frame for said pixel locations of said pixels corresponding to significant dark current in said low-light image, wherein said pixel locations are of pixels with significant dark current in said low-light image having pixel values lower than said pixels with significant dark current in said dark frame;
- subtracting the unmarked dark frame pixels from said low-light image, forming a resulting image;
- replacing the marked pixel values with pixel values according to a pixel replacement algorithm, forming a corrected resulting image;
- and
- and outputting said corrected resulting image.
A digital camera for improving the quality of low-light images, said images formed from pixels, said digital camera comprising:
- a memory to store pixel values of an original picture image;
- a memory to store pixel values of a dark frame associated with said original picture image;
- a processor to subtract the pixel values of the dark frame from the pixel values of the original picture image, forming a subtracted image therefrom, to analyze the subtracted image for illegal pixel values, and to replace the illegal pixel values according to a pixel replacement algorithm, forming a corrected image therefrom;
- and
- a memory to store the corrected image.
Dependencies are inferred from the claim text.