如何在图像中的点周围绘制正方形

Question

I have a binary image, with white points. How can I identify and draw a square around these points using OpenCV?

The problem is that the points are very small, and so far all the attempts have failed to find all the points.

This is the input image:

This is the result I am interested in:

Is there a possibility using a function of OpenCV? And if not, (because of size), what is the most effective way?

Answer 1

1. Apply dilate on your image with size 5.

2. If distance of between dots < 10, they will be joined to one big dot.

3. If distance > 10, it will be seperated as it is.

4. Find contours on result.

5. Get minAreaRect of each contours.

6. Done.

Answer 2

Using following method you can find a solution.

Full code for the solution:

import cv2
import numpy as np
img = cv2.imread('test.jpg', 0)
output_img = img.copy()
cv2.threshold(img,0,255,cv2.THRESH_BINARY+cv2.THRESH_OTSU,img)

kernel = np.ones((50,70), np.uint8)
img = cv2.dilate(img, kernel, iterations=1)


im2,contours, hier = cv2.findContours(img.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
for c in contours:
    # get the bounding rect
    x, y, w, h = cv2.boundingRect(c)
    # draw a white rectangle to visualize the bounding rect
    cv2.rectangle(output_img, (x, y), (x + w, y + h), 255, 1)

cv2.imshow('output',output_img)
cv2.waitKey(0)

• First you have to create a kernel according to your requirement.

• Bigger the kernel size, points belong to a cluster will be higher.

• Then using cv2.dilate method you should dilate the image using created kernel.

• After that you should find contours of dilated image and get the bounding rectangle of those contours.

• One rectangle can be considered as one cluster. You can change the cluster size using kernel = np.ones((50,70), np.uint8) In here it is 50 x 70.

OUTPUT: