Histogram Equalization on specific area using mask-CodePudding

I am working with images that I need to process. However, only specific areas of these images are of interest so for each image I have a corresponding mask (that can be of any shape, not a bounding box or anything specific). I would like to do Histogram Equalization but only on the "masked surface" as I am not interested in the rest of the image.

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The following is the mask:

mask = cv2.imread('mask.jpg', 0)

I want to perform histogram equalization only on the flower.

Store the coordinates where pixels are white (255) in mask:

coord = np.where(mask == 255)

Store all pixel intensities on these coordinates present in gray:

pixels = gray[coord]

Perform histogram equalization on these pixel intensities:

equalized_pixels = cv2.equalizeHist(pixels)

Create a copy of gray named gray2. Place the equalized intensities in the same coordinates:

gray2 = gray.copy()
for i, C in enumerate(zip(coord[0], coord[1])):
    gray2[C[0], C[1]] = equalized_pixels[i][0]

cv2.imshow('Selective equalization', gray2)

Comparison:

Note: This process can be extended for Histogram Equalization or CLAHE, ON RGB or grayscale images.