How to Hide Secret Messages in Photos with Python and OpenCV

1. Code Idea

First read the target photo with cv2.imread, then create a same‑size white canvas using PIL.Image.new, and finally draw characters onto each block of the image based on the chosen text.

2. Complete Python Code

# -*- coding:utf-8 -*-
from PIL import Image, ImageDraw, ImageFont
import cv2

font_path = './font-family/MiNiJianPangWa-1.ttf'

def draw(image_path, draw_text):
    img = cv2.imread(image_path)  # read image file
    img_temp = Image.new("RGB", [img.shape[1], img.shape[0]], "white")  # create white canvas
    drawObj = ImageDraw.Draw(img_temp)  # drawing object
    n = 8  # block interval
    m = 8  # font size
    font = ImageFont.truetype(font_path, size=m)
    for i in range(0, img.shape[0], n):
        for j in range(0, img.shape[1], n):
            drawObj.text([j, i], draw_text[int(j / n) % len(draw_text)],
                         fill=(img[i][j][2], img[i][j][1], img[i][j][0]), font=font)
    img_temp.save('img_' + image_path)

draw('bingbing.jpg', "都是冰冰的")  # you can modify the text

3. Code Adjustments

The font_path must point to a valid TrueType font file you download yourself; different fonts produce different visual effects. Both m (font size) and n (block interval) are configurable, but values of 8 for each give the best result in most tests.

Result

Original photo (use a high‑resolution image for better quality):

Resulting image – the hidden text is invisible at normal view but becomes clear when zoomed in:

Because the enlarged image may appear blurry, you can use an online lossless upscaling tool (choose the highest denoise level) to improve clarity.