Separating the leaf from it's background

I have a set of images, all of which look almost like this leaf here:

I want to extract the leaf from the background, for which I used the GrabCut algorithm as used here.

As a different approach, I also used thresholding based on ratios of r, g and b values as here:

import numpy as np
import cv2
import matplotlib.pyplot as plt

testImg = cv2.imread('path_to_the_image')
testImg = cv2.resize(testImg, (256, 256))
#bgImg = cv2.imread('')
#blurBg = cv2.GaussianBlur(bgImg, (5, 5), 0)
#blurBg = cv2.resize(blurBg, (256, 256))

#testImg = cv2.GaussianBlur(testImg, (5, 5), 0)
cv2.imshow('testImg', testImg)
#plt.imshow(bgImg)
cv2.waitKey(0)
#plt.show()

modiImg = testImg.copy()    
ht, wd = modiImg.shape[:2]

print(modiImg[0][0][0])

for i in range(ht):
    for j in range(wd):
        r = modiImg[i][j][0]
        g = modiImg[i][j][1]
        b = modiImg[i][j][2]

        r1 = r/g
        r2 = g/b
        r3 = r/b

        r4 = round((r1+r2+r3)/3, 1)

        if g > r and g > b:
            modiImg[i][j] = [255, 255, 255]
        elif r4 >= 1.2:
            modiImg[i][j] = [255, 255, 255]
        else:
            modiImg[i][j] = [0, 0, 0]

        # if r4 <= 1.1:
        #   modiImg[i][j] = [0, 0, 0]
        # elif g > r and g > b:
        #   modiImg[i][j] = [255, 255, 255]
        # else:
        #   modiImg[i][j] = [255, 255, 255]
        # elif r4 >= 1.2:
        #   modiImg[i][j] = [255, 255, 255]
        # else:
        #   modiImg[i][j] = [0, 0, 0]


plt.imshow(modiImg)
plt.show()

testImg = testImg.astype(float)

alpha = modiImg.astype(float) / 255

testImg = cv2.multiply(alpha, testImg)                

cv2.imshow('final', testImg/255)
cv2.waitKey(0)

But the dark spots on the leaf always go missing in the extracted leaf image as shown here:

Is there any other method to separate the leaf from its background, given that there is only one leaf per image, and the background is almost the same for other images that I have and also the leaves are positioned almost similarly as in here.

You can try image segmentation using HSV colormap.

Code:

img =  cv2.imread('leaf.jpg')
hsv = cv2.cvtColor(img, cv2.COLOR_BGR2HSV)

# find the green color 
mask_green = cv2.inRange(hsv, (36,0,0), (86,255,255))
# find the brown color
mask_brown = cv2.inRange(hsv, (8, 60, 20), (30, 255, 200))
# find the yellow color in the leaf
mask_yellow = cv2.inRange(hsv, (21, 39, 64), (40, 255, 255))

# find any of the three colors(green or brown or yellow) in the image
mask = cv2.bitwise_or(mask_green, mask_brown)
mask = cv2.bitwise_or(mask, mask_yellow)

# Bitwise-AND mask and original image
res = cv2.bitwise_and(img,img, mask= mask)

cv2.imshow("original", img)
cv2.imshow("final image", res)
cv2.waitKey(0)
cv2.destroyAllWindows()

Output:

Moreover, If you change lower range of yellow color from (21, 39, 64) to (14, 39, 64), then you will see that the small black spots present on the leaf start filling and will improve the result even further.