Opencv Python Remove Certain Objects In An Image

i am using python with opencv and numpy, to detect stars in astronomical for example this one1 images. Using template matching I have got it to detect stars with a threshold (click

Solution 1:

You may create a mask, and use cv2.inpaint for replacing the selected "mask area" using the pixel near the area boundary.

Since you didn't post 'template.jpg', I created the following one:

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• Building a mask by drawing filled rectangles on zeros image:

   mask = np.zeros_like(imageG)
   for pt inzip(*loc[::-1]):
       #a = cv2.rectangle(image, pt, (pt[0] + w, pt[1] + h), (0,0,255), 1)
       cv2.rectangle(mask, (pt[0]+3, pt[1]+3), (pt[0]+w-3, pt[1]+h-3), 255, -1)  # Reduce the size of the rectangle by 3 pixels from each side.

  Note: I used cv2.rectangle for keeping your original code, but I think circles may by better in your case.

• Using inpaint for removing the masked area:

  image = cv2.inpaint(image, mask, 2, cv2.INPAINT_NS)
  

  You may tune the parameters.

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Here is the complete code:

import cv2
import numpy as np
import time

start = time.time()
threshold = 0.4
image = cv2.imread('lag.jpg')
imageG = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

#template = cv2.imread('template.jpg', 0)
template = cv2.imread('template.png', 0)
w, h = template.shape[::-1]
res = cv2.matchTemplate(imageG,template,cv2.TM_CCOEFF_NORMED)
loc = np.where( res >= threshold)


mask = np.zeros_like(imageG)
for pt in zip(*loc[::-1]):
    #a = cv2.rectangle(image, pt, (pt[0] + w, pt[1] + h), (0,0,255), 1)
    cv2.rectangle(mask, (pt[0]+3, pt[1]+3), (pt[0]+w-3, pt[1]+h-3), 255, -1)  # Reduce the size of the rectangle by 3 pixels from each side


image = cv2.inpaint(image, mask, 2, cv2.INPAINT_NS)

cv2.imshow('lag.jpg', image)
cv2.imshow('mask', mask)
end = time.time()
final = end - start
print(final)
cv2.waitKey(0)
cv2.destroyAllWindows()

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Results:

mask:

image (after inpaint):

Original image (for comparison):

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You may improve the solution using few sizes of rectangles (or circles) - use larger rectangles for covering the larger stars.