Stego Problem from CTF

Hi guys,

So I need help on this CTF problem. I feel like I'm doing something really wrong. The hint doesn't make much sense to me because if I mod every pixel by 8, the image becomes black.

Here's the image:

https://2017.pactf.com/static/ctfproblems/3557f4d6-96b2-43fe-844d-ab115f2f78b2/trees.b4a84e2a04e5.png

Description:

There’s an image of some trees here. I bet the image contains more than trees, though.

Hint given:

Try mod 8?

Do you know how the flag looks like? I've found a hidden message, but it doesn't look like a flag to me rather than a hint.

The problem is called "Trees" so I'm pretty sure anything to do with Trees is probably the flag.

https://github.com/zardus/ctf-tools/blob/master/stegsolve/install

Play with that!

WTF Stegsolve is amazing. dont_miss_the_flag_for_the_trees But what does "Red plane" and "Green Plane" mean?

I'm not entirely sure about that. It's a RGB sorcery :o

Kinda related: https://www.mathworks.com/matlabcentral/answers/309680-why-does-the-red-plane-contain-the-whole-image

If someone roughly knows, please ELI5 for us :|