Anyone know how to trace a low-opacity or faint watermark using Python?

I'm working on an image-processing project and ran into a challenge.

Does anyone have experience detecting or tracing very low-opacity (faint) watermarks using Python? I'm not trying to remove them—just identify or highlight where they exist.

I've been looking into approaches like:

• OpenCV (contrast enhancement, edge detection, frequency analysis)
• Pillow for basic preprocessing
• FFT/DCT-based techniques
• Template matching (when a watermark pattern is known)

If you've solved a similar problem or know of a good library, research paper, or technique, I'd really appreciate your suggestions.

What approach worked best for you?