When utilizing OpenCV to remove the background from an image, the result may often appear black if the alpha channel (transparency) is not appropriately managed or displayed.

I have made an effort to refine your code. While I cannot guarantee its absolute perfection for your specific requirements, I hope it proves helpful. However, if the corrected OpenCV code does not meet your expectations, you might consider using the Python library rembg, which often delivers excellent results.

For your convenience, I have provided both the corrected OpenCV code and an example using rembg below.

Corrected opencv:

import cv2
import numpy as np

# Function to check if background removal is needed
def is_background_removal_needed(image_path):
    image = cv2.imread(image_path, cv2.IMREAD_GRAYSCALE)
    if image is None:
       raise FileNotFoundError(f"Image not found: {image_path}")

    variance = np.var(image)
    print(f"Image variance: {variance:.2f}")
    return variance > 100  # Threshold for variance

# Function to remove background and save transparent image
def remove_background(image_path, output_path):
    image = cv2.imread(image_path)
    if image is None:
        raise FileNotFoundError(f"Image not found: {image_path}")

    gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    _, mask = cv2.threshold(gray, 200, 255, cv2.THRESH_BINARY_INV)

    # Add transparency
    original = image.copy()
    # Create an alpha channel based on the mask
    b, g, r = cv2.split(original)
    alpha = mask

    # Merge BGR channels with the alpha channel
    output = cv2.merge((b, g, r, alpha))

    cv2.imwrite(output_path, output)
    print(f"Background removed and saved to: {output_path}")

# Main process function
def process_image(image_path, output_path):
     if is_background_removal_needed(image_path):
         print("Background removal is needed. Processing...")
         remove_background(image_path, output_path)
     else:
         print("Background removal is NOT needed. Saving the original image.")
         image = cv2.imread(image_path)
         cv2.imwrite(output_path, image)
         print(f"Original image saved to: {output_path}")

# Input and output paths
input_image = "example_img.jpg"  # Path to input image
output_image = "output_image.png"

# Run the process
process_image(input_image, output_image)

Using rembg:

from rembg import remove
from PIL import Image
import io

# Load input image
input_path = 'example_img.jpg'
output_path = 'output_image.png'

with open(input_path, 'rb') as inp_file:
     input_image = inp_file.read()

# Remove the background
output_image = remove(input_image)

# Save the output image (transparent background as PNG)
with open(output_path, 'wb') as out_file:
     out_file.write(output_image)

print(f"Background removed. Saved to {output_path}")