Method and system for cleaning images to highlight information recorded on a background surface

• US 20030156118A1
• Filed: 02/20/2002
• Published: 08/21/2003
• Est. Priority Date: 02/19/2002
• Status: Abandoned Application

• Current Assignee: Smart Technologies Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Smart Technologies Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Ayinde, Olugbenga
• Application Number:
  US10/077,814
• Publication Number:
  US 20030156118A1
• Time in Patent Office: Days
• US Class Current: 345/589
• CPC Class Codes: G06T 5/94 based on local image properties, e.g. for local contrast enhancement
• CPC Class Codes: G06T 7/11 Region-based segmentation
• CPC Class Codes: G06T 7/194 involving foreground-background segmentation

Abstract

A method of cleaning an image of a background surface on which information has been recorded includes for each pixel p_ij in the image, creating an array holding grayscale values of neighbor pixels within a region surrounding the pixel p_ij. The average grayscale value of the neighbor pixels is calculated and then thresholded. The grayscale value of the pixel p_ij is compared with the thresholded average grayscale value. If the grayscale value of the pixel p_ij is darker than the thresholded average grayscale value, the pixel is retained. Otherwise, the pixel value is set to bright. For each retained pixel, the colour value of the pixel p_ij and an average colour value are used to determine the output colour of the retained pixel in the cleaned image.

Claims

1. A method of cleaning an image of a background surface on which information has been recorded, said method comprising the steps of:

for each pixel p_ij under consideration that is in said image;

comparing the pixel p_ij with neighbor pixels within a region surrounding said pixel p_ij to determine whether said pixel p_ij represents recorded information or said background surface; and

if the pixel p_ij represents said background surface, assigning the pixel p_ij a value to contrast pixels representing recorded information.

2. The method of claim 1 wherein each pixel p_ij in said image is under consideration.

3. The method of claim 2 wherein the colour values of pixels representing recorded information are retained in said image and wherein the values of pixels representing said background surface are set to a bright value.

4. The method of claim 3 wherein said bright value is white.

5. The method of claim 4 wherein said region is centered around said pixel p_ij.

6. The method of claim 5 wherein said region is determined by a region value N, said region value N designating an N×

N region of pixels centered around said pixel p_ij, selected pixels within said N×

N region being designated as neighbor pixels.

7. The method of claim 6 wherein said neighbor pixels are determined by an interval value M, said interval value M designating every Mth pixel in said region as a neighbor pixel.

8. The method of claim 7 wherein during the comparing the average grayscale value of said neighbor pixels is compared with the grayscale value of said pixel p_ij.

9. The method of claim 8 wherein the average grayscale value is thresholded prior to said comparing.

10. The method of claim 9 wherein during thresholding, the average grayscale value is multiplied by a threshold value less than 1, said pixel p_ij being determined to represent recorded information if said pixel p_ij is darker than the thresholded average grayscale value.

11. The method of claim 11 further comprising the step of adjusting the colour of pixels representing recorded information to compensate for colour added to said image during capturing thereof by a camera.

12. The method of claim 11 wherein during said adjusting the average colour of said image is determined thereby to determine the colour added to said image.

13. The method of claim 11 wherein during said adjusting the average colour of pixels in said region is determined thereby to determine the colour added to said image.

14. A method of cleaning an image of a background surface on which information has been recorded, said method comprising the steps of:

for each pixel p_ij in said image;

creating an array holding grayscale values of neighbor pixels within a region surrounding said pixel p_ij;

calculating the average grayscale value of said neighbor pixels and thresholding said average grayscale value;

comparing the grayscale value of the pixel p_ij with the thresholded average grayscale value; and

retaining the pixel p_ij in said image if the grayscale value of said pixel differs from said thresholded average grayscale value, otherwise setting the value of the pixel p_ij to contrast pixels p_ij retained in said image.

15. The method of claim 14 further comprising the step of adjusting the colour of each retained pixel to compensate for colour added to said image during capturing thereof by a camera.

16. The method of claim 15 wherein during said adjusting, an average colour value representing the added colour is used to adjust the colour of pixels p_ijretained in said image.

17. The method of claim 15 wherein during setting, the value of the pixel p_ij is set to white and wherein pixels p_ij having grayscale values darker than the thresholded average grayscale value are retained in said image.

18. The method of claim 17 wherein said region is centered around said pixel p_ij.

19. The method of claim 18 wherein said creating step includes the steps of using a region value N to determine the size of the region surrounding the pixel p_ijand using an interval value M to determine the pixels within said region that are designated as neighbor pixels.

20. The method of claim 19 wherein said region value N designates a region including N×

N pixels surrounding said pixel p_ij and wherein said interval value designates every Mth pixel in said region as a neighbor pixel.

22. The method of claim 20 wherein during said thresholding said average grayscale value is multiplied by a threshold value having a value in the range of from about 0.90 to 0.95.

23. The method of claim 22 where said creating step further includes the step of padding said array with additional grayscale pixel values copied from the margins of said image.

24. The method of claim 23 wherein the padding on each side of the array has a width equal to one half of the width of said region value.

25. The method of claim 16 wherein said average colour value is determined from the average colour of said image.

26. The method of claim 16 wherein said average colour value is determined from the average colour of pixels within said region.

27. A computer product including a computer program embodied thereon for cleaning an image of a background surface on which information has been recorded, said computer program comprising:

computer program code for comparing each pixel p_ij under consideration that is in said image with neighbor pixels within a region surrounding said pixel p_ij to determine whether said pixel p_ij represents recorded information or said background surface; and

computer program code for assigning the pixel p_ij under consideration a value to contrast pixels representing recorded information if the pixel p_ij represents said background surface.

28. A computer product according to claim 27 further comprising computer program code for adjusting the colour of pixels representing recorded information to compensate for colouring effects introduced into said image during image capture.

29. A computer product according to claim 28 wherein said computer program code for adjusting calculates the average colour of said image to determine the colouring effect and uses the average colour of said image to adjust the colour of pixels representing recorded information.

30. A computer product according to claim 28 wherein said computer program code for adjusting calculates the average colour of said region to determine the colouring effect and uses the average colour of said region to adjust the colour of pixels representing recorded information.

31. A computer product according to claim 28 wherein said computer program code for comparing compares the value of each pixel p_ij with the values of neighbor pixels to determine whether the value of the pixel p_ij appears to be the same as a threshold number of neighbor pixels and hence represents the background surface.

32. A computer product according to claim 31 wherein said computer program code for comparing compares the value of each pixel p_ij with the average pixel value of said neighbor pixels within an N×

N region of pixels centered around and surrounding said pixel p_ij, every Mth pixel in said region being designated as a neighbor pixel.

33. A camera-based system for capturing an image of a target area comprising:

a generally horizontally extending boom assembly, said boom assembly being positioned above a background surface;

at least one digital camera mounted on said boom assembly at a location spaced from the plane of said background surface, said at least one digital camera being oriented so that the field of view thereof encompasses said background surface; and

a controller in communication with said at least one digital camera, said controller receiving image data from said at least one digital camera and processing said image data to form a cleaned digital image of said background surface, during said cleaning said controller retaining only pixels representing information recorded on said background surface.

34. A camera-based system according to claim 33 wherein during cleaning said controller, for each pixel p_ij under consideration that is in said image:

compares the pixel p_ij with neighbor pixels within a region surrounding said pixel p_ij to determine whether said pixel p_ij represents recorded information or said background surface; and

if the pixel p_ij represents said background surface, assigns the pixel p_ija value to contrast pixels representing recorded information.

35. A camera-based system according to claim 34 wherein said controller retains the colour values of pixels representing recorded information in said image sets the values of pixels representing said background surface to white.

36. A camera-based system according to claim 35 wherein said region is determined by a region value N, said region value N designating an N×

N region of pixels centered around said pixel p_ij, selected pixels within said N×

N region being designated as neighbor pixels.

37. A camera-based system according to claim 36 wherein said neighbor pixels are determined by an interval value M, said interval value M designating every Mth pixel in said region as a neighbor pixel.

38. A camera-based system according to claim 37 wherein said controller compares the average grayscale value of said neighbor pixels with the grayscale value of said pixel p_ij to determine whether to retain said pixel in said cleaned image.

39. A camera-based system according to claim 38 wherein said controller further adjusts the colour of pixels represented recorded information to compensate for colour added to said image during capturing thereof by said at least one camera.