Tone mapping for low-light video frame enhancement
View Patent ↗A technique is provided for generating sharp, well-exposed, color images from low-light images. A series of under-exposed images is acquired. A mean image is computed and a sum image is generated each based on the series of under-exposed images. Chrominance variables of pixels of the mean image are mapped to chrominance variables of pixels of the sum image. Chrominance values of pixels within the series of under-exposed images are replaced with chrominance values of the sum image. A set of sharp, well-exposed, color images is generated based on the series of under-exposed images with replaced chrominance values.
1. A method of generating sharp, well-exposed, color images from low-light images, comprising:
acquiring a series of under-exposed images;
computing a mean image based on an average of multiple images of the series of under-exposed images;
generating a sum image based on a sum of multiple images of the series of under-exposed images;
mapping chrominance variables of pixels of the mean image to chrominance variables of pixels of the sum image;
replacing chrominance values of pixels within the series of under-exposed images with chrominance values of the sum image; and
generating a set of sharp, well-exposed, color images based on the series of under-exposed images with replaced chrominance values.
2. The method of claim 1 , wherein the acquiring of said series of under-exposed images comprises capturing raw images and generating processed RGB images based on the raw images.
3. The method of claim 2 , wherein the computing of said mean image comprises applying a tone-mapping transformation to the series of under-exposed images.
4. The method of claim 3 , wherein the tone-mapping transformation comprises a logarithmic transformation.
5. The method of claim 2 , wherein the acquiring of said series of under-exposed images further comprises applying a tone-mapping transformation to the series of under-exposed images.
6. The method of claim 5 , wherein the tone-mapping transformation comprises a logarithmic transformation.
7. The method of claim 1 , wherein the acquiring of said series of under-exposed images comprises applying a tone-mapping transformation to the series of under-exposed images.
8. The method of claim 7 , wherein the tone-mapping transformation comprises a logarithmic transformation.
9. The method of claim 1 , further comprising transforming the mean and sum images to YUV space prior to mapping and replacing said chrominance values.
10. The method of claim 9 , further comprising transforming the under-exposed images with replaced chrominance values back to RGB space.
11. The method of claim 1 , wherein the set of sharp, well-exposed, color images comprises multiple video images.
12. The method of claim 1 , wherein the set of sharp, well-exposed, color images comprise one or more still images.
13. A digital video acquisition device, comprising:
a lens and an image sensor for capturing a stream of multiple digital video or still images;
a processor; and
a memory having processor-readable code embedded therein for programming the processor to perform a method of generating sharp, well-exposed, color images from under-exposed, low-light images, wherein the method comprises:
acquiring a series of under-exposed images;
computing a mean image based on an average of multiple images of the series of under-exposed images;
generating a sum image based on a sum of multiple images of the series of under-exposed images;
mapping chrominance variables of pixels of the mean image to chrominance variables of pixels of the sum image;
replacing chrominance values of pixels within the series of under-exposed images with chrominance values of the sum image; and
generating a set of sharp, well-exposed, color images based on the series of under-exposed images with replaced chrominance values.
14. The device of claim 13 , wherein the acquiring of said series of under-exposed images comprises capturing raw images and generating processed RGB images based on the raw images.
15. The device of claim 14 , wherein the computing of said mean image comprises applying a tone-mapping transformation to the series of under-exposed images.
16. The device of claim 15 , wherein the tone-mapping transformation comprises a logarithmic transformation.
17. The device of claim 14 , wherein the acquiring of said series of under-exposed images further comprises applying a tone-mapping transformation to the series of under-exposed images.
18. The device of claim 17 , wherein the tone-mapping transformation comprises a logarithmic transformation.
19. The device of claim 13 , wherein the acquiring of said series of under-exposed images comprises applying a tone-mapping transformation to the series of under-exposed images.
20. The device of claim 19 , wherein the tone-mapping transformation comprises a logarithmic transformation.
21. The device of claim 13 , wherein the method further comprises transforming the mean and sum images to YUV space prior to mapping and replacing said chrominance values.
22. The device of claim 21 , wherein the method further comprises transforming the under-exposed images with replaced chrominance values back to RGB space.
23. The device of claim 13 , wherein the set of sharp, well-exposed, color images comprises multiple video images.
24. The device of claim 13 , wherein the set of sharp, well-exposed, color images comprise one or more still images.
25. One or more non-transitory processor-readable media having processor-readable code embedded therein for programming one or more processors to perform a method of generating sharp, well-exposed, color images from under-exposed, low-light images, wherein the method comprises:
acquiring a series of under-exposed images;
computing a mean image based on an average of multiple images of the series of under-exposed images;
generating a sum image based on a sum of multiple images of the series of under-exposed images;
mapping chrominance variables of pixels of the mean image to chrominance variables of pixels of the sum image;
replacing chrominance values of pixels within the series of under-exposed images with chrominance values of the sum image; and
generating a set of sharp, well-exposed, color images based on the series of under-exposed images with replaced chrominance values.
26. The one or more non-transitory processor-readable media of claim 25 , wherein the acquiring of said series of under-exposed images comprises capturing raw images and generating processed RGB images based on the raw images.
27. The one or more non-transitory processor-readable media of claim 26 , wherein the computing of said mean image comprises applying a tone-mapping transformation to the series of under-exposed images.
28. The one or more non-transitory processor-readable media of claim 27 , wherein the tone-mapping transformation comprises a logarithmic transformation.
29. The one or more non-transitory processor-readable media of claim 26 , wherein the acquiring of said series of under-exposed images further comprises applying a tone-mapping transformation to the series of under-exposed images.
30. The one or more non-transitory processor-readable media of claim 29 , wherein the tone-mapping transformation comprises a logarithmic transformation.
31. The one or more non-transitory processor-readable media of claim 25 , wherein the acquiring of said series of under-exposed images comprises applying a tone-mapping transformation to the series of under-exposed images.
32. The one or more non-transitory processor-readable media of claim 31 , wherein the tone-mapping transformation comprises a logarithmic transformation.
33. The one or more non-transitory processor-readable media of claim 25 , wherein the method further comprises transforming the mean and sum images to YUV space prior to mapping and replacing said chrominance values.
34. The one or more non-transitory processor-readable media of claim 33 , wherein the method further comprises transforming the under-exposed images with replaced chrominance values back to RGB space.
35. The one or more non-transitory processor-readable media of claim 25 , wherein the set of sharp, well-exposed, color images comprises multiple video images.
36. The one or more non-transitory processor-readable media of claim 25 , wherein the set of sharp, well-exposed, color images comprise one or more still images.