How can I remove small pixel clusters from a transparent png using python

Question

I am trying to remove random pixel clusters noise from a transparent png using python.

I have used eroding and then dilating like this

import cv2
import numpy as np

img = cv2.imread('test1.png')
blurred_img = cv2.medianBlur(img, 1)

kernel = np.ones((2,2),np.uint8)
erosion = cv2.erode(blurred_img, kernel, iterations=1)
output = cv2.dilate(erosion, kernel, iterations=1)

cv2.imwrite('output.png', output)

but this blurs the image to the point where it loses a lot of details:

I have tried many alternatives but I just can’t obtain the result I want… The original image just without that random pixel noise around it. I hope someone can help me.

Asked By: Dreghici Vlad

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Source

Answer 1

area_opening from skimage can be used on the alpha channel. We use the cv2.IMREAD_UNCHANGED flag to get this channel and modify it.

the following code has an output

import cv2
import numpy as np
from skimage.morphology import area_opening

img = cv2.imread('test.png', cv2.IMREAD_UNCHANGED)
img[:,:,3][area_opening(img[:,:,3], 7) == 0] = 0
cv2.imwrite('output.png', img)

Answered By: arrmansa

How can I remove small pixel clusters from a transparent png using python

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