>>63355
The automated method is a whole bunch of math. Basically the standard alpha-blending equation is:
color = A*alpha + B*(1-alpha)
where A and B are (r,g,b) vectors and alpha is a number between 0 and 1. If you know some of those values, you can rearrange it to form a set of simultaneous equations which give you the watermark. Then you just run the equation in reverse on a target image to remove the watermark.
I can post the code and a more in-depth description of the math if you want.
But that wasn't really necessary here. The image is made up of large sections of uniform color. Just use the color picker tool to select the right color from an untainted part of the image, then use a small brush tool and a steady hand to paint over that part of the watermark.