How to Add and Remove Image Watermarks Using Python (PIL & OpenCV)

In the digital media era, image watermarking is essential for copyright protection, brand identification, and content authentication, and Python offers simple ways to add or remove watermarks.

Example 1: Adding a text watermark with the PIL library

from PIL import Image, ImageDraw, ImageFont

def add_text_watermark(image_path, output_path, text, position):
    image = Image.open(image_path)
    draw = ImageDraw.Draw(image)
    font = ImageFont.truetype("arial.ttf", 36)
    draw.text(position, text, font=font, fill=(255, 255, 255))
    image.save(output_path)

add_text_watermark('original.jpg', 'watermarked.jpg', 'My Watermark', (10, 10))

Example 2: Adding a semi‑transparent image watermark with PIL

from PIL import Image

def add_image_watermark(base_image_path, watermark_image_path, output_path):
    base_image = Image.open(base_image_path)
    watermark = Image.open(watermark_image_path).convert("RGBA")
    # Set watermark opacity
    alpha = 0.3
    watermark.putalpha(int(255 * alpha))
    # Position at bottom‑right corner
    position = (base_image.width - watermark.width, base_image.height - watermark.height)
    base_image.paste(watermark, position, watermark)
    base_image.save(output_path)

add_image_watermark('original.jpg', 'logo.png', 'watermarked_with_logo.jpg')

Example 3: Batch adding watermarks to a folder of images

from PIL import Image
import os

def batch_add_watermark(images_dir, watermark_path, output_dir):
    watermark = Image.open(watermark_path).convert("RGBA")
    alpha = 0.3
    watermark.putalpha(int(255 * alpha))
    for filename in os.listdir(images_dir):
        if filename.endswith('.jpg'):
            base_image = Image.open(os.path.join(images_dir, filename))
            position = (base_image.width - watermark.width, base_image.height - watermark.height)
            base_image.paste(watermark, position, watermark)
            base_image.save(os.path.join(output_dir, filename))

batch_add_watermark('images', 'logo.png', 'output')

Example 4: Adding a rotated watermark using OpenCV

import cv2
import numpy as np

def add_rotated_watermark(image_path, watermark_path, output_path):
    img = cv2.imread(image_path)
    watermark = cv2.imread(watermark_path, cv2.IMREAD_UNCHANGED)
    # Resize watermark
    scale_percent = 10  # percent of original size
    width = int(watermark.shape[1] * scale_percent / 100)
    height = int(watermark.shape[0] * scale_percent / 100)
    dim = (width, height)
    watermark = cv2.resize(watermark, dim, interpolation=cv2.INTER_AREA)
    # Rotate watermark
    rows, cols, _ = watermark.shape
    M = cv2.getRotationMatrix2D((cols/2, rows/2), 45, 1)
    watermark = cv2.warpAffine(watermark, M, (cols, rows))
    # Blend watermark onto image
    for c in range(0, 3):
        img[:rows, :cols, c] = watermark[:,:,c]*watermark[:,:,3]/255 + img[:rows, :cols, c]*(1-watermark[:,:,3]/255)
    cv2.imwrite(output_path, img)

add_rotated_watermark('original.jpg', 'logo.png', 'watermarked_rotated.jpg')

Example 5: Simple watermark removal using blur (advanced)

# Removing a watermark is complex; this example uses a basic blur on the watermark area.
import cv2
import numpy as np

def remove_watermark(image_path, watermark_area, output_path):
    img = cv2.imread(image_path)
    # Blur the specified region
    img[watermark_area[1]:watermark_area[1]+watermark_area[3], watermark_area[0]:watermark_area[0]+watermark_area[2]] = \
        cv2.blur(img[watermark_area[1]:watermark_area[1]+watermark_area[3], watermark_area[0]:watermark_area[0]+watermark_area[2]], (10, 10))
    cv2.imwrite(output_path, img)

remove_watermark('watermarked.jpg', [10, 10, 200, 200], 'cleaned.jpg')

By following these examples, you can master basic techniques for adding and removing watermarks with Python, which are useful for protecting copyrights or enhancing visual projects, and you are encouraged to explore further tutorials on image processing, machine learning, and data science.