METHOD, DEVICE, AND SYSTEM FOR PERFORMING COLOR ENHANCEMENT ON WHITEBOARD COLOR IMAGE

• US 20120081548A1
• Filed: 08/15/2011
• Published: 04/05/2012
• Est. Priority Date: 09/30/2010
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Zhang, Wenbo, Li, Yan
• Granted Patent: US 8,860,806 B2
• Time in Patent Office: Days
• US Class Current: 348/143
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 7/194 involving foreground-background segmentation
• CPC Class Codes: G06V 30/1423 the instrument generating sequences of position coordinates corresponding to handwriting preprocessing or recognising digital ink G06V30/32
• CPC Class Codes: H04N 5/77 between a recording apparatus and a television camera
• CPC Class Codes: H04N 7/183 for receiving images from a single remote source
• CPC Class Codes: H04N 9/646 for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters
• CPC Class Codes: H04N 9/806 with processing of the sound signal

Abstract

Disclosed are a device, a method, and a system for enhancing color. The device comprises a unit used to extract a foreground portion from a whiteboard color image to serve as whiteboard contents; a unit used to stretch R, G, and B channel values of each of a plurality of foreground pixels forming the whiteboard contents; a unit used to adjust color tone of each of the foreground pixels; a unit used to adjust a ratio of color saturation degree to color intensity of each of the foreground pixels so as to cause the ratio to approach a ratio expectation value; and a unit used to increase the color saturation degree and the color intensity of each of the foreground pixel so as to cause the two to approach a color saturation degree expectation value and a color intensity expectation value I_d, respectively.

Claims

1. A color enhancement device for carrying out color enhancement with regard to a whiteboard color image comprising:

a whiteboard content extraction unit used to extract a foreground portion from the whiteboard color image, and let the foreground portion serve as whiteboard contents;

a color channel stretch unit used to stretch R, G, and B channel values of each of a plurality of foreground pixels forming the extracted whiteboard contents;

a color tone adjustment unit used to adjust, under a condition where color intensity of each of the foreground pixels is unchanged, color tone of the corresponding foreground pixel;

a saturation degree to intensity ratio adjustment unit used to adjust, under a condition where the color tone of each of the foreground pixels is unchanged, a ratio of color saturation degree to color intensity of the corresponding foreground pixel so as to cause the ratio to approach a predetermined ratio expectation value r_d; and

a saturation degree and intensity increase unit used to increase, under a condition where the color tone of each of the foreground pixels is unchanged, the color saturation degree and the color intensity of the corresponding foreground pixel so as to cause the two to approach a predetermined color saturation degree expectation value S_d and a predetermined color intensity expectation value I_d, respectively.

2. The color enhancement device according to claim 1, wherein:

the whiteboard content extraction unit extracts the foreground portion by calculating brightness, color saturation degree, and color intensity of a pixel in the whiteboard color image according to the following equations;

L(R,G,B)=0.299*R+0.587*G+0.114*B;

S(R,G,B)=1-3Min(R,G,B)/(R+G+B); and

I(R,G,B)=((R+G+B)/255)/3,

wherein,

the L stands for the brightness, the S stands for the color saturation degree, and I stands for the color intensity.

3. The color enhancement device according to claim 2, wherein:

If the brightness value of the pixel is greater than a predetermined brightness threshold value, the color saturation degree value of the pixel is greater than a predetermined color saturation degree threshold value, and the color intensity value of the pixel is greater than a predetermined color intensity threshold value, then it is determined that the pixel belongs to the foreground portion.

4. The color enhancement device according to claim 3, wherein:

the color channel stretch unit stretches the R, G, and B channel values of each of the foreground pixels by employing the following equation;

5. The color enhancement device according to claim 4, wherein:

the color tone adjustment unit does not change the color intensity of each of the foreground pixels by letting the sum of the R, G, and B channel values of the corresponding foreground pixel be unchanged.

6. The color enhancement device according to claim 5, wherein:

the color tone adjustment carried out by the color tone adjustment unit is realized by adjusting the R, G, and B channel values of each of the foreground pixels so as to cause the intermediate one of the three channel values of the corresponding foreground pixel to be equal to the minimum one of the three channel values of the corresponding foreground pixel,

wherein, the three channel values after the color tone adjustment satisfy the following equations;

Max′

=Max+d1;

Mid′

=Mid−

2*d1;

Min′

=Min+d1; and

Mid−

2*d1=Min+d1,

wherein, Max′

, Mid′

, and Min′

stand for the maximum one, the intermediate one, and the minimum one of the three channel values of the corresponding foreground pixel after the color tone adjustment;

Max, Mid, and Min stand for the maximum one, the intermediate one, and the minimum one of the three channel values of the corresponding foreground pixel before the color tone adjustment; and

d1 stands for first adjustment amount,

wherein, by considering that the three channel values of the corresponding foreground pixel ranges between 0 to 255 and employing the following relationships;

7. The color enhancement device according to claim 6, wherein:

the ratio of color saturation degree to color intensity of each of the foreground pixels is defined as follows;

r=color saturation degree/color intensity,

the saturation degree to intensity ratio adjustment unit does not change the color tone of each of the foreground pixels by subtracting second adjustment amount d2 from the R, G, and B channel values of the corresponding foreground pixel, i.e., (R′

, G′

, B′

)=(R−

d2, G−

d2, B−

d2), wherein, (R′

, G′

, B′

) stands for the three channel values of the corresponding foreground pixel after the ratio adjustment, and (R, G, B) stands for original values of the three channels of the corresponding foreground pixel,

wherein, the three channel values of the corresponding foreground pixel adjusted by the saturation degree to intensity ratio adjustment unit satisfy the following relationships;

8. The color enhancement device according to claim 7, wherein:

the saturation degree and intensity increase unit does not change the color tone of each of the foreground pixels by subtracting third adjustment amount d3 from the R, G, and B channel values of the corresponding pixel, i.e., (R2, G2, B2)=(R−

d3, G−

d3, B−

d3), wherein, (R2, G2, B2) stands for the three channel values of the corresponding foreground pixel after the color saturation degree increase, and (R, G, B) stands for the original values of the three channels of the corresponding foreground pixel,

the saturation degree and intensity increase unit increases the color saturation degree of each of the foreground pixels so as to cause the color saturation degree of the corresponding foreground pixel to satisfy the following relationship;

9. The color enhancement device according to claim 8, wherein:

the saturation degree and intensity increase unit increases the color intensity of each of the foreground pixels by multiplying the R, G, and B channel values of the corresponding foreground pixel by a coefficient K, i.e., (R2′

, G2′

, B2′

)=K*(R2, G2, B2)=(K*R2, K*G2, K*B2), wherein, (R2′

, G2′

, B2′

) stands for the three channel values of the corresponding foreground pixel after the color intensity increase;

(R2, G2, B2) stands for the three channel values of the corresponding foreground pixel after the color saturation degree increase; and

the coefficient K is defined as K=Id/I2, and I2 stands for color intensity of the corresponding pixel whose R, G, and B channel values are (R2, G2, B2).

10. A color enhancement method of carrying out color enhancement with regard to a whiteboard color image comprising:

a whiteboard content extraction step of extracting a foreground portion from the whiteboard color image, and letting the foreground portion serve as whiteboard contents;

a color channel stretch step of stretching R, G, and B channel values of each of a plurality of foreground pixels forming the extracted whiteboard contents;

a color tone adjustment step of adjusting, under a condition where color intensity of each of the foreground pixels is unchanged, color tone of the corresponding foreground pixel;

a saturation degree to intensity ratio adjustment step of adjusting, under a condition where the color tone of each of the foreground pixels is unchanged, a ratio of color saturation degree to color intensity of the corresponding foreground pixel so as to cause the ratio to approach a predetermined ratio expectation value r_d; and

a saturation degree and intensity increase step of increasing, under a condition where the color tone of each of the foreground pixels is unchanged, the color saturation degree and the color intensity of the corresponding foreground pixel so as to cause the two to approach a predetermined color saturation degree expectation value S_d and a predetermined color intensity expectation value I_d, respectively.

11. The color enhancement method according to claim 10, wherein:

in the whiteboard content extraction step, the foreground portion is extracted by calculating brightness, color saturation degree, and color intensity of a pixel in the whiteboard color image according to the following equations;

L(R,G,B)=0.299*R+0.587*G+0.114*B;

S(R,G,B)=1-3Min(R,G,B)/(R+G+B); and

I(R,G,B)=((R+G+B)/255)/3,

wherein,

the L stands for the brightness, the S stands for the color saturation degree, and I stands for the color intensity.

12. The color enhancement method according to claim 11, wherein:

in the whiteboard content extraction step, if the brightness value of the pixel is greater than a predetermined brightness threshold value, the color saturation degree value of the pixel is greater than a predetermined color saturation degree threshold value, and the color intensity value of the pixel is greater than a predetermined color intensity threshold value, then it is determined that the pixel belongs to the foreground portion.

13. The color enhancement method according to claim 12, wherein:

in the color channel stretch step, the R, G, and B channel values of each of the foreground pixels are stretched by employing the following equation;

14. The color enhancement method according to claim 13, wherein:

in the color tone adjustment step, the sum of the R, G, and B channel values of each of the foreground pixels is unchanged.

15. The color enhancement method according to claim 14, wherein:

in the color tone adjustment step, the R, G, and B channel values of each of the foreground pixels are adjusted so as to cause the intermediate one of the three channel values of the corresponding foreground pixel to be equal to the minimum one of the three channel values of the corresponding foreground pixel,

wherein, the three channel values after the color tone adjustment in the color tone adjustment step satisfy the following equations;

Max′

=Max+d1;

Mid′

=Mid−

2*d1;

Min′

=Min+d1; and

Mid−

2*d1=Min+d1,

wherein, Max′

, Mid′

, and Min′

stand for the maximum one, the intermediate one, and the minimum one of the three channel values of the corresponding foreground pixel after the color tone adjustment;

Max, Mid, and Min stand for the maximum one, the intermediate one, and the minimum one of the three channel values of the corresponding foreground pixel before the color tone adjustment; and

d1 stands for first adjustment amount,

wherein, by considering that the three channel values of the corresponding foreground pixel ranges between 0 to 255 and employing the following relationships;

16. The color enhancement method according to claim 15, wherein:

the ratio of color saturation degree to color intensity of each of the foreground pixels is defined as follows;

r=color saturation degree/color intensity,

in the saturation degree to intensity ratio adjustment step, second adjustment amount d2 is subtracted from the R, G, and B channel values of the corresponding foreground pixel, i.e., (R′

, G′

, B′

)=(R−

d2, G−

d2, B−

d2), wherein, (R′

, G′

, B′

) stands for the three channel values of the corresponding foreground pixel after the ratio adjustment, and (R, G, B) stands for original values of the three channels of the corresponding foreground pixel,

wherein, the three channel values of the corresponding foreground pixel adjusted in the saturation degree to intensity ratio adjustment step satisfy the following relationships;

17. The color enhancement method according to claim 16, wherein:

in the saturation degree and intensity increase step, third adjustment amount d3 is subtracted from the R, G, and B channel values of the corresponding pixel, i.e., (R2, G2, B2)=(R−

d3, G−

d3, B−

d3), wherein, (R2, G2, B2) stands for the three channel values of the corresponding foreground pixel after the color saturation degree increase, and (R, G, B) stands for the original values of the three channels of the corresponding foreground pixel,

in the saturation degree and intensity increase step, the color saturation degree of each of the foreground pixels is increased so as to cause the color saturation degree of the corresponding foreground pixel to satisfy the following relationship;

18. The color enhancement method according to claim 17, wherein:

in the saturation degree and intensity increase step, the color intensity of each of the foreground pixels is increased by multiplying the R, G, and B channel values of the corresponding foreground pixel by a coefficient K, i.e., (R2′

, G2′

, B2′

)=K*(R2, G2, B2)=(K*R2, K*G2, K*B2), wherein, (R2′

, G2′

, B2′

) stands for the three channel values of the corresponding foreground pixel after the color intensity increase;

(R2, G2, B2) stands for the three channel values of the corresponding foreground pixel after the color saturation degree increase; and

the coefficient K is defined as K=Id/I2, and I2 stands for color intensity of the corresponding pixel whose R, G, and B channel values are (R2, G2, B2).

19. A whiteboard content sharing system comprising:

a video capture unit used to capture contents written on a whiteboard by a local user with a color whiteboard marker pen, and output the contents as a digital image;

a calculation unit used to obtain a whiteboard color image including whiteboard contents by carrying out image subtraction with regard to a whiteboard image captured by the video capture unit and a remotely shared whiteboard image transferred from a remote system, and carry out color enhancement with regard to the whiteboard color image;

a data transfer unit used to receive the shared whiteboard image from the remote system via a network, and send the whiteboard contents obtained by the calculation unit to the remote system; and

a projection unit used to projecting the shared whiteboard image received from the remote system and the whiteboard contents obtained by the calculation unit on a screen for display,

wherein,

the calculation unit includes;

a whiteboard content extraction unit used to extract a foreground portion from the whiteboard color image, and let the foreground portion serve as the whiteboard contents;

a color channel stretch unit used to stretch R, G, and B channel values of each of a plurality of foreground pixels forming the extracted whiteboard contents;

a color tone adjustment unit used to adjust, under a condition where color intensity of each of the foreground pixels is unchanged, color tone of the corresponding foreground pixel;

a saturation degree to intensity ratio adjustment unit used to adjust, under a condition where the color tone of each of the foreground pixels is unchanged, a ratio of color saturation degree to color intensity of the corresponding foreground pixel so as to cause the ratio to approach a predetermined ratio expectation value r_d; and

a saturation degree and intensity increase unit used to increase, under a condition where the color tone of each of the foreground pixels is unchanged, the color saturation degree and the color intensity of the corresponding foreground pixel so as to cause the two to approach a predetermined color saturation degree expectation value S_d and a predetermined color intensity expectation value I_d, respectively.