System and method of determining nitrogen levels from a digital image

• US 8,391,565 B2
• Filed: 05/24/2010
• Issued: 03/05/2013
• Est. Priority Date: 05/24/2010
• Status: Active Grant

• Current Assignee: The Board of Trustees of the University of Arkansas (University of Arkansas System)
• Original Assignee: The Board of Trustees of the University of Arkansas (University of Arkansas System)
• Inventors: Rorie, Robert L., Purcell, Larry C, Karcher, Douglas E
• Primary Examiner(s): Lu, Tom Y
• Application Number:
  US12/800,849
• Publication Number:
  US 20110286636A1
• Time in Patent Office: 1,016 Days
• Field of Search: 382/110
• US Class Current: 382/110
• CPC Class Codes: G01N 2021/8466 Investigation of vegetal material, e.g. leaves, plants, fruits
• CPC Class Codes: G01N 21/25 Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
• CPC Class Codes: G01N 21/84 Systems specially adapted for particular applications
• CPC Class Codes: G06T 7/0012 Biomedical image inspection
• CPC Class Codes: G06V 10/56 relating to colour

Abstract

A system and method of determining nitrogen levels from a digital image. In particular, a method of determining leaf nitrogen concentration and yield from a digital photograph of a fully developed leaf (collared leaf) of a crop of nonlegumes, such as corn, rice, wheat, cotton, potatoes or sugarcane. The digital image is processed to determine a dark green color index (“DGCI”), which is closely related to leaf nitrogen concentration and yield. Standardized color disks having known DGCI values are included in the digital photograph and serve as an internal standard. The internal standard allows correction of DGCI of samples when using different cameras and/or when lighting conditions change.

Claims

1. A method for determining nitrogen levels of a nonlegume plant, said method comprising the steps of:

a. acquiring an image with digital photography of a colored leaf from a crop of nonlegume plants with a background, said image further comprising an internal standard to account for differences in cameras or lighting conditions or both of said digital photography, and said background having a color in a portion of the visible spectrum away from the visible spectrum of the color of said leaf;

b. performing an algorithm to determine a corrected dark green color index of said leaf in said image; and

c. determining leaf nitrogen sufficiency or deficiency of said leaf in said image from said corrected dark green color index.

2. The method of claim 1 wherein said internal standard is a plurality of standardized color disks having a predetermined shape and a color representing a color value ranging from severely nitrogen deficient to nitrogen sufficient of said leaf.

3. The method of claim 2 wherein said standardized color disks further comprises a first standardized color disk having a yellow color representing a severely nitrogen deficient leaf and a second standardized disk having a dark green color representing a nitrogen sufficient leaf.

4. The method of claim 2 further comprising the step of placing said standardized color disks a distance away from said leaf during said digital photography to minimize any shadows between said leaf and said standardized color disks.

5. The method of claim 2 wherein said algorithm recognizes said shape of said standardized color disks and uses said standardized color disks as said internal standard to adjust for different cameras or lighting conditions or both.

6. The method of claim 1 wherein said color of said background is pink.

7. The method of claim 1 wherein said nonlegume plant is selected from the group consisting of corn, rice, wheat, cotton, potatoes or sugarcane.

8. The method of claim 1 further comprising the step of acquiring said image through a network connection.

9. The method of claim 2 wherein said algorithm comprising the steps of:

a. calculating a dark green color index of said leaf in said image;

b. calculating a dark green color index of said standardized color disks in said image; and

c. calculating a corrected leaf dark green color index from said dark green color index of said leaf and said dark green color index of said standardized color disks.

10. The method of claim 9 wherein said step of calculating said dark green color index of said leaf in said image further comprises the steps of:

a. obtaining absolute red, green and blue values of said leaf in said image;

b. converting said absolute red, green and blue values to percentage red, green and blue values of said leaf in said image;

c. converting said percentage red, green and blue values to absolute hue, saturation and brightness values of said leaf in said image;

d. calculating average hue, saturation and brightness values from said absolute hue, saturation and brightness values of said leaf in said image; and

e. converting said average hue, saturation and brightness values to said dark green color index of said leaf in said image.

11. The method of claim 10 wherein said dark green color index of said leaf in said image encompasses a dark green color on a scale of zero (0) to one (1) with values closer to one (1) representing a darker green.

12. The method of claim 9 wherein said step of calculating a dark green color index of said standardized color disks in said image further comprises the steps of:

a. obtaining absolute red, green and blue values of said standardized color disks in said image;

b. converting said absolute red, green and blue values to percentage red, green and blue values of said standardized color disks in said image;

c. converting said percentage red, green and blue values to absolute hue, saturation and brightness values of said standardized color disks in said image;

d. calculating average hue, saturation and brightness values from said absolute hue, saturation and brightness values of said standardized color disks in said image; and

e. converting said average hue, saturation and brightness values to said dark green color index of said standardized color disks in said image.

13. The method of claim 12 wherein said dark green color index of said standardized color disks in said image encompasses a dark green color on a scale of zero (0) to one (1) with values closer to one (1) representing a darker green.

14. The method of claim 1 further comprising the step of estimating yield of said crop from said image as a function of said corrected dark green color index.

15. The method of claim 14 further comprising the step of transmitting said yield of said crop.

16. The method of claim 1 further comprising the step of estimating yield of said crop from said image based on said leaf nitrogen sufficiency or deficiency.

17. The method of claim 1 further comprising transmitting said leaf nitrogen sufficiency or deficiency.

18. A system comprising:

at least one electronic device for taking an image of a colored leaf from a crop of said nonlegume plant;

an image background having a color in a portion of the visible spectrum away from the visible spectrum of the color of said leaf;

an internal standard to account for differences in cameras or lighting conditions or both of said image; and

a central processing unit communicably attached to said electronic device via a network connection for performing an algorithm to determine a corrected dark green color index of said leaf in said image.

19. The system of claim 18 wherein said electronic device comprises a digital camera or a handheld electronic device having a camera and an algorithm to determine a corrected dark green color index of said leaf in said image.

20. The system of claim 18 wherein said internal standard are standardized color disks having a predetermined shape and a color representing a color value ranging from severely nitrogen deficient to nitrogen sufficient of said leaf.

21. The system of claim 20 wherein said standardized color disks further comprises a first standardized color disk having a yellow color representing a severely nitrogen deficient leaf and a second standardized disk having a dark green color representing a nitrogen sufficient leaf.

22. The system of claim 18 wherein said nonlegume plant is selected from the group consisting of corn, rice, wheat, cotton, potatoes or sugarcane.

23. A system for determining nitrogen levels of a nonlegume plant, said system comprising:

an electronic device for taking an image of a colored leaf from a crop of said nonlegume plant;

an external standard having a color in a portion of the visible spectrum away from the visible spectrum of the color of said leaf;

an internal standard to account for differences in cameras or lighting conditions or both of said image, said internal standard representing a color value ranging from severely nitrogen deficient to nitrogen sufficient of said leaf; and

a central processing unit communicably attached to said electronic device via a network connection for performing an algorithm to determine a corrected dark green color index of said leaf in said image.

24. The system of claim 23 wherein said electronic device comprises a digital camera or a handheld electronic device having a camera and an algorithm to determine a corrected dark green color index of said leaf in said image.

25. The system of claim 23 wherein said internal standard are standardized color disks having a predetermined shape.

26. The system of claim 25 wherein said standardized color disks further comprises a first standardized color disk having a yellow color representing a severely nitrogen deficient leaf and a second standardized disk having a dark green color representing a nitrogen sufficient leaf.

27. The system of claim 23 wherein said nonlegume plant is selected from the group consisting of corn, rice, wheat, cotton, potatoes or sugarcane.