Python: Showing every Object of an image in its own window

Question

I've written some code, to crop an object (in this case the Data Matrix Code) from an image:

import numpy as np
import cv2

image = cv2.imread("datamatrixc.png")
img_gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

img_height, img_width = image.shape[:2]

WHITE = [255, 255, 255]

# Threshold filter
ret, thresh = cv2.threshold(img_gray, 127, 255, cv2.THRESH_BINARY_INV)

# Get Contours
_, contours, _ = cv2.findContours(thresh, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

# Get Last element of the contours object
max = len(contours) - 1

cnt = contours[max]

# Get coordinates for the bounding box  
x, y, w, h = cv2.boundingRect(cnt)

image_region = image[ int(((img_height / 2) - h) / 2) : int(((img_height / 2) - h) / 2 + h), int(x): int(x + w) ]
dmc = cv2.copyMakeBorder(image_region, 10, 10, 10, 10, cv2.BORDER_CONSTANT, value = WHITE)

cv2.imshow("Test", dmc)
cv2.waitKey(0)
cv2.destroyAllWindows()

The code works fine and I received as result:

However, the next image is a little more complicated. I receive the same result as in the previous image, but I have no idea how to detect the two other objects.

Is there an easier way every object showing in its window?

score 2 · Answer 1 · answered Aug 06 '18 at 12:08

For this specific image take the biggest contours you have and check if the object is 4 sided shape.If the half-point between the bounding box's corners (see pairs below) is in the contour array then voila, problem solved.

Pairs : TopRight-TopLeft, TopRight-BottomRight, TopLeft-BottomLeft, BottomLeft-BottomRight

Or you could check if there pixels that are not black/white inside the bounding box ?

And for the ploting individualy just slap a for on what you allready have

score 1 · Accepted Answer · answered Aug 07 '18 at 03:22

How about this?

import numpy as np
import cv2

image = cv2.imread("datamatrixc.png")
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

ret, bin_img = cv2.threshold(gray, 0, 255, cv2.THRESH_BINARY_INV + cv2.THRESH_OTSU)

kernel = np.ones((3,3),np.uint8)
closing = cv2.morphologyEx(bin_img, cv2.MORPH_CLOSE, kernel, iterations=4)

n_labels, labels, stats, centroids = cv2.connectedComponentsWithStats(bin_img)

size_thresh = 5000

for i in range(1, n_labels):
    if stats[i, cv2.CC_STAT_AREA] >= size_thresh:
        print(stats[i, cv2.CC_STAT_AREA])
        x = stats[i, cv2.CC_STAT_LEFT]
        y = stats[i, cv2.CC_STAT_TOP]
        w = stats[i, cv2.CC_STAT_WIDTH]
        h = stats[i, cv2.CC_STAT_HEIGHT]

        cv2.imshow('img', image[y:y+h, x:x+w])
        cv2.waitKey(0)

Python: Showing every Object of an image in its own window

2 Answers2