Unwatermarking

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1) Question: What are translucent watermarks?
Answer: the shitty translucent logos put by raws websites on your waifus/husbandos
WM cropped.png

2) Question: How are translucent watermarks made?
Answer: by image blending.
Each watermarked pixel is a mix of an original pixel of the image with a pixel of the shitty logo. Maybe there is 50% of each. Or maybe it's 80% and 20%. And maybe it's not the same for each pixel. The value of the proportion of the watermark's pixel is named the "alpha".

3) Question: Is the watermarking reversible?
Answer: if it is a translucent watermark and you happen to know have that logo and its alpha values, then yes, you can revert the mathematical watermarking operation. But keep in mind it won't be a 100% restoration of the original, especially if you work with JPEG images (that format does lossy compression, so you don't have full quality).

4) Question: Ok, but how do I get the logo and the alpha?
Answer: You need to compare two reference images are watermarked. Typically, you'll pick a black background and a white background. Then you'll compare the values of each watermarked pixel of the two images, and with a bit of maths you'll be able to reconstruct the logo's pixels and the alpha values used for the blending.

5) Question: Are the watermark maths difficult?
Answer: If you can solve a system of two linear equations with two unknowns, you can do it. Grab paper, pencils, and get in a comfortable place & mood to meditate, and you can do it.

6) Question: Are there programs I can use to reconstruct the watermarks and to unwatermark?
Answer: Yes. There are currently action scripts for Photoshop, python scripts, C programs, executables for Windows, HTML pages with JavaScript programs. These tools are not instant magic, though, and although using them can save you the trouble of redrawing the watermarks entirely, you will sometimes need to build up a bit of know-how.

7) Question: How to master this topic?
Answer: Understand how it works, practice, write your own programs. You will learn various details about digital images and programs in the process, and you may encounter some advanced topics like the hell of colour profiles, weird non-standard shit done by Photoshop and Windows, etc.

8) Question: Can I do anything to remove an opaque watermark?
Answer: Not with unwatermarking. Content-aware filling may help in some cases. In all other cases, silicon microchips bustling with electrons won't replace the skill and creativity of natural brain cells.

9) Question: Where can I find someone to ask about that kind of stuff?
Answer: If you really want to find such, you will. Lurk on the scanlation community's Discord server. Maybe someone will know someone else who knows. That topic is not unheard of at Scanlator School.
 
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