Segmenting products on the shelf - opencv

Question

I am trying to detect edges from the products on a shelf using histogram projections. But I am stuck at 2 levels.
The challenges that I m facing are:
How to get the longest non shelf segment from the image i.e Detect the width of the widest product on the shelf from the available one.
How to achieve morphological reconstruction using custom markers.To eliminate
all small horizontal segments, I am generating 2 markers which can be seen in 'markers.png' (Attached). With them, I am calculating the minimum of the reconstruction outputs from both the markers.
Need assistance on this.
Thanks a lot
Below is my python code for the same.
Below is my python code
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import numpy as np
import cv2 as cv
from matplotlib import pyplot as plt
import math
# Read the input image
img = cv.imread('C:\\Users\\672059\\Desktop\\p2.png')
# Converting from BGR to RGB. Default is BGR.
# img_rgb = cv.cvtColor(img, cv.COLOR_BGR2RGB)
# Resize the image to 150,150
img_resize = cv.resize(img, (150, 150))
# Get the dimensions of the image
img_h, img_w, img_c = img_resize.shape
# Split the image on channels
red = img[:, :, 0]
green = img[:, :, 1]
blue = img[:, :, 2]
# Defining a vse for erosion
vse = np.ones((img_h, img_w), dtype=np.uint8)
# Morphological Erosion for red channel
red_erode = cv.erode(red, vse, iterations=1)
grad_red = cv.subtract(red, red_erode)
# Morphological Erosion for green channel
green_erode = cv.erode(green, vse, iterations=1)
grad_green = cv.subtract(green, green_erode)
# Morphological Erosion for blue channel
blue_erode = cv.erode(blue, vse, iterations=1)
grad_blue = cv.subtract(blue, blue_erode)
# Stacking the individual channels into one processed image
grad = [grad_red, grad_green, grad_blue]
retrieved_img = np.stack(grad, axis=-1)
retrieved_img = retrieved_img.astype(np.uint8)
retrieved_img_gray = cv.cvtColor(retrieved_img, cv.COLOR_RGB2GRAY)
plt.title('Figure 1')
plt.imshow(cv.bitwise_not(retrieved_img_gray), cmap=plt.get_cmap('gray'))
plt.show()
# Hough Transform of the image to get the longest non shelf boundary from the image!
edges = cv.Canny(retrieved_img_gray, 127, 255)
minLineLength = img_w
maxLineGap = 10
lines = cv.HoughLinesP(edges, 1, np.pi/180, 127, minLineLength=1, maxLineGap=1)
temp = img.copy()
l = []
for x in range(0, len(lines)):
for x1, y1, x2, y2 in lines[x]:
cv.line(temp, (x1, y1), (x2, y2), (0, 255, 0), 2)
d = math.sqrt((x2-x1)**2 + (y2-y1)**2)
l.append(d)
# Defining a hse for erosion
hse = np.ones((1, 7), dtype=np.uint8)
opening = cv.morphologyEx(retrieved_img_gray, cv.MORPH_OPEN, hse)
plt.title('Figure 2')
plt.subplot(1, 2, 1), plt.imshow(img)
plt.subplot(1, 2, 2), plt.imshow(cv.bitwise_not(opening), 'gray')
plt.show()
# Dilation with disk shaped structuring element
horizontal_size = 7
horizontalstructure = cv.getStructuringElement(cv.MORPH_ELLIPSE, (horizontal_size, 1))
dilation = cv.dilate(opening, horizontalstructure)
plt.title('Figure 3')
plt.imshow(cv.bitwise_not(dilation), 'gray')
plt.show()
# Doing canny edge on dilated image
edge = cv.Canny(dilation, 127, 255)
plt.title('Figure 4')
plt.imshow(edges, cmap='gray')
plt.show()
h_projection = edge.sum(axis=1)
print(h_projection)
plt.title('Projection')
plt.plot(h_projection)
plt.show()
listing = []
for i in range(1, len(h_projection)-1):
if h_projection[i-1] == 0 and h_projection[i] == 0:
listing.append(dilation[i])
listing.append(dilation[i-1])
a = np.array([np.array(b) for b in l])
h = len(l)
_, contours, _ = cv.findContours(a, cv.RETR_EXTERNAL, cv.CHAIN_APPROX_SIMPLE)
x, y, w, h = cv.boundingRect(contours[0])
y = y + i - h
cv.rectangle(img, (x, y), (x + w, y + h), (255, 0, 0), 2)
l.clear()
plt.imshow(img)
plt.show()
# Generating a mask
black_bg = np.ones([img_h, img_w], dtype=np.uint8)
# Clone the black bgd image
left = black_bg.copy()
right = black_bg.copy()
# Taking 10% of the image width
ten = int(0.1 * img_w)
left[:, 0:ten+1] = 0
right[:, img_w-ten:img_w+1] = 0
plt.title('Figure 4')
plt.subplot(121), plt.imshow(left, 'gray')
plt.subplot(122), plt.imshow(right, 'gray')
plt.show()
# Marker = left and right. Mask = dilation
mask = dilation
marker_left = left
marker_right = right
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markers.png link: https://i.stack.imgur.com/45WJ6.png
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Answer 1

Based on you input image, I would :
take a picture of an empty fridge
then compare the current image with the empty one.
play with morphological operations
get connected components > size N
If you can't take a empty fridge image:
segment the shelves (threshold white parts)
undo do the rotation of the image by using image moments of the shelves
for each shelve:
Threshold on saturation
Do a vertical projection
Count maxima.
Tresholded:
Erode-dilate:
Connected componens (width > 10 * height + > minsize):
And you have shelves.
Now take the average Y form each shelf and cut the original image in pieces:
Dither to 8 colors:
and threshold:
Connected components (h>1.5*w, minsize... this is hard here, I played with it :)