Quote from: quest_777 on April 13, 2018, 03:46:35 PM

Wow man,

Can you please specify this delta image thing? I really want to make everything as honest as possible. I can reward you with MFC currency if you have a wallet for this tip.

I'm not sure they call it delta image in literature, but here's a brief explanation of it:

An image is essentially an array of pixels, each pixel is a vector of numbers that represent the Red/Blue/Green (RBG) components (or any other representation format).
I have the current image that you uploaded without the characters, when you upload the new image, I'll download it and now I have 2 images, subtract the values in each pixel in image 1 from the values of the corresponding pixel in image 2, now you have an image (array of pixels) that contains the difference between the 2 images, so you can see exactly which pixels were modified.
Pixels with low modified values (that can't be distinguished by human eye) can be zeroed out to reduce the "noise" of the image, this results in an image with only pixels that have significant change between the 2 images, all that's needed is to run some algorithm to detect those small characters locations (group of neighbor pixels)
-Drop any group with small number of pixels (ex: drop all groups with less than 9 pixels since you can't possibly write a character with them), so far the user only knows the location of the characters and can inspect them visually to extract the seed. This process can also be automated by simply adding another component that takes those pixel groups and perform character recognition algorithm on it.

That is how I'd go around scripting this contest, but I'm just an amateur in this and have used the naive approach, pretty sure anyone with decent knowledge in image processing can do much better job and explain in better technical details on how this is carried.

However, it's not impossible to defend against those "attacks", I have couple ideas that I'll PM you about (so others won't be prepared for them), as I said I'm not a professional so it's given that my defenses are week and will only stall algorithms. Also, the resulting image will loos some quality (due to changed pixels).

I'm afraid it's the first time I've heard about MFC, I'll make sure to read about it.