Adaptive contrast optimization of digital color images
원문보기
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
G06K-009/40
G06K-009/00
H04N-001/40
출원번호
UP-0464645
(2006-08-15)
등록번호
US-7796830
(2010-10-04)
발명자
/ 주소
Bilcu, Radu
Vehvilainen, Markku
출원인 / 주소
Nokia Corporation
대리인 / 주소
Banner & Witcoff, Ltd.
인용정보
피인용 횟수 :
0인용 특허 :
11
초록▼
Methods and systems are provided for adjusting the contrast and intensity of digital images. Digital images may be processed by first creating a histogram that identifies the intensity of components of the digital image. A transformation function is then computed using the histogram. The transformat
Methods and systems are provided for adjusting the contrast and intensity of digital images. Digital images may be processed by first creating a histogram that identifies the intensity of components of the digital image. A transformation function is then computed using the histogram. The transformation function can be used to adjust the intensity of a low light portion of the digital image and is applied to individual color components of the digital image. Finally, the contrast of a portion of the digital image other than the low light portion of the digital image is adjusted.
대표청구항▼
We claim: 1. A method comprising: (a) computing an intensity image that identifies the intensity of pixels of an input image; (b) creating a histogram of the intensity image; (c) computing a transformation function, using a first side of the histogram, that can be used to adjust the intensity of a
We claim: 1. A method comprising: (a) computing an intensity image that identifies the intensity of pixels of an input image; (b) creating a histogram of the intensity image; (c) computing a transformation function, using a first side of the histogram, that can be used to adjust the intensity of a low light portion of the digital image; (d) applying the transformation function to individual color components of the digital image; and (e) applying a contrast enhancement to each transformed color component, wherein the contrast enhancement of a color component is based on computation of a gain map of the color component, said gain map computed using a parameter of the first transformation function. 2. The method of claim 1, wherein (a) comprises determining the intensity of red, green and blue pixels. 3. The method of claim 1, wherein the individual color components comprise red, green and blue color components. 4. The method of claim 1, wherein (c) comprises: (i) estimating a maximum number of pixels in a low light portion of the histogram; (ii) estimating a width of the low light portion of the histogram by determining a range that has intensity values that exceed a minimum intensity threshold; and (iii) computing the transformation function to apply to the low light portion of the digital image. 5. The method of claim 1, wherein (d) further comprises preserving minimum and maximum intensity values of each of the individual color components. 6. The method of claim 1, further including: (e) adjusting the contrast of a portion of the digital image other than the low light portion of the digital image. 7. The method of claim 1, wherein the adjustment in (e) is a function of the transformation function. 8. The method of claim 1, further comprising correcting oversaturation of pixels by computing the average between each of the color components, processed using the transformation function, and a corresponding original color component. 9. The method of claim 1 wherein applying a contrast enhancement comprises computing, for each pixel of a color component, a difference between a value of the each pixel and a value of a pixel situated either above or below the each pixel, and computing a difference between the value of the each pixel and of a pixel situated to either the left or right of the each pixel; and said method further comprising; computing, for each pixel of the color component, a sum of the value of the each pixel and the value of the pixel situated either above or below the each pixel, and computing a sum between the value of the each pixel and the pixel situated to either the left or right of the each pixel. 10. The method of claim 9, wherein applying the contrast enhancement comprises multiplying the computed differences with corresponding values of the corresponding gain map and averaging the results with the computed sums. 11. A method, comprising: (a) computing an intensity image that identifies the intensity of pixels of an input image; (b) creating a histogram of the intensity image; (c) computing a transformation function, using a first side of the histogram, that can be used to adjust the intensity of a low light portion of the digital image; and (d) applying the transformation function to individual color components of the digital image, wherein (a) comprises computing an intensity image y(i,j), such that y ( i , j ) = r ( i , j ) + b ( i , j ) + g ( i , j ) 3 where i identifies a pixel row and j identifies a pixel column and r(i,j), g(i,j) and b(i,j) are the intensities of red, green and blue color components of the input image. 12. The method of claim 11, wherein the histogram of the intensity image y(i,j) is defined such that h(m)=nr of pixels in the range [m−0.5;m+0.5] with m=0, . . . , 255. 13. An apparatus comprising: a sensor that captures digital images; a processor programmed with computer-executable instructions that, when executed, cause the apparatus to: (a) compute an intensity image that identifies the intensity of pixels of the captured digital image; (b) create a histogram of the intensity image; (c) compute a transformation function, using the histogram, that can be used to adjust the intensity of a low light portion of the captured digital image; (d) apply the transformation function to individual color components of the captured digital image; and (e) apply a contrast enhancement to each transformed color component, wherein the contrast enhancement of a color component is based on computation of a gain map of the color component, said gain map computed using a parameter of the first transformation function. 14. The apparatus of claim 13, wherein the apparatus comprises a digital camera. 15. The apparatus of claim 13, wherein the apparatus comprises a mobile terminal. 16. The apparatus of claim 13, wherein (a) comprises computing an intensity image y(i,j), such that y ( i , j ) = r ( i , j ) + b ( i , j ) + g ( i , j ) 3 where i identifies a pixel row and j identifies a pixel column and r(i,j), g(i,j) and b(i,j) are the red, green and blue color components of the captured digital image. 17. The apparatus of claim 13, wherein the histogram of the intensity image y(i,j) is defined such that h(m)=nr of pixels in the range [m−0.5;m+0.5] with m=0, . . . , 255. 18. The apparatus of claim 13, wherein (c) comprises: (i) estimating a maximum number of pixels in a low light portion of the histogram; (ii) estimating a width of the low light portion of the histogram by determining a range that has intensity values that exceed a minimum intensity threshold; and (iii) computing the transformation function to apply to the low light portion of the captured digital image. 19. The apparatus of claim 13, wherein the processor is further programmed with computer-executable instructions to: (e) adjust the contrast of a portion of the captured digital image other than the low light portion of the captured digital image. 20. A non-transitory computer-readable medium containing computer-executable instructions that, when executed by a processor: (a) create a histogram that identifies the intensity of components of a digital image; (b) compute a transformation function, using the histogram, that can be used to adjust the intensity of a low light portion of the digital image; (c) apply the transformation function to individual color components of the digital image; (d) adjust the contrast of a portion of the digital image other than the low light portion of the digital image; and (e) apply a contrast enhancement to each transformed color component, wherein the contrast enhancement of a color component is based on computation of a gain map of the color component, said gain map computed using a parameter of the first transformation function. 21. The non-transitory computer-readable medium of claim 20, wherein (b) comprises (i) estimating a maximum number of pixels in a low light portion of the histogram; (ii) estimating a width of the low light portion of the histogram by determining a range that has intensity values that exceed a minimum intensity threshold; and (iii) computing the transformation function to apply to the low light portion of the captured digital image.
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이 특허에 인용된 특허 (11)
Loveland Radon B. (Las Cruces NM), Automatic shutter for low light sensing and amplifying device.
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Taniguchi, Nobuyuki; Ishikawa, Norio; Akada, Yasuaki; Egawa, Takeshi; Kawamura, Kunio, Device for providing a camera system with an information for a focus adjustment.
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