Question 1

So I've been trying to make bounding boxes around a couple of fruits that I made in paint. I'm a total beginner to opencv so I watched a couple tutorials and the code that I typed made, makes contours around the object and using that I create bounding boxes. However it makes way too many tiny contours and bounding boxes. For example, heres the initial picture: enter image description here

and heres the picture after my code runs: enter image description here

However this is what I want:

enter image description here

Heres my code:

import cv2
import numpy as npimg = cv2.imread(r'C:\Users\bob\Desktop\coursera\coursera-2021\project2\fruits.png')grayscaled = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
blur = cv2.GaussianBlur(grayscaled, (7,7), 1)
canny = cv2.Canny(blur, 50, 50)
img1 = img.copy()
all_pics = []contours, Hierarchy = cv2.findContours(canny, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)for cnt in contours:peri = cv2.arcLength(cnt, True)approx = cv2.approxPolyDP(cnt, 0.02*peri, True)x, y, w, h = cv2.boundingRect(approx)bob = img [y:y+h, x:x+w]all_pics.append((x, bob))cv2.rectangle(img1, (x, y), (x+w, y+h), (0, 255, 0), 2)cv2.imshow("title", img1)
cv2.waitKey(0)

Question 2

I think FloodFill in combination with FindContours can help you:

import os
import cv2
import numpy as np# Read original image
dir = os.path.abspath(os.path.dirname(__file__))
im = cv2.imread(dir+'/'+'im.png')# convert image to Grayscale and Black/White
gry = cv2.cvtColor(im, cv2.COLOR_BGR2GRAY)
cv2.imwrite(dir+'/im_1_grayscale.png',gry)
bw=cv2.threshold(gry, 127, 255, cv2.THRESH_BINARY)[1]
cv2.imwrite(dir+'/im_2_black_white.png',bw)# Use floodfill to identify outer shape of objects
imFlood = bw.copy()
h, w = bw.shape[:2]
mask = np.zeros((h+2, w+2), np.uint8)
cv2.floodFill(imFlood, mask, (0,0), 0)
cv2.imwrite(dir+'/im_3_floodfill.png',imFlood)# Combine flood filled image with original objects
imFlood[np.where(bw==0)]=255
cv2.imwrite(dir+'/im_4_mixed_floodfill.png',imFlood)# Invert output colors
imFlood=~imFlood
cv2.imwrite(dir+'/im_5_inverted_floodfill.png',imFlood)# Find objects and draw bounding box
cnts, _ = cv2.findContours(imFlood, cv2.RETR_TREE, cv2.CHAIN_APPROX_NONE)
for cnt in cnts:peri = cv2.arcLength(cnt, True)approx = cv2.approxPolyDP(cnt, 0.02*peri, True)x, y, w, h = cv2.boundingRect(approx)bob = im[y:y+h, x:x+w]cv2.rectangle(im, (x, y), (x+w, y+h), (0, 255, 0), 2)# Save final image
cv2.imwrite(dir+'/im_6_output.png',im)

Grayscale and black/white:

enter image description here