I made a post which explain how to make a basic tweak that changes the color of the screenshot. Now, if you have a good knowledge in Objective-c, you can make others (and better) tweaks.
When you want to make a tweak, you hook a system file to inject a new code to be run. You can hook a lot of different files that make a lot of different things. But to hook a file, you have to know his name and the methods that are in it.
The files are in .h, you can find them in /var/sdk/usr/local/include. The most you will normally use are in /var/sdk/usr/local/include/SpringBoard. To open a file, just tap on it and choose “Text editor” or maybe it will be open without asking that. When you are in it, you can see all the methods (-(void)…).
In the first post, we made a tweak that changes the color of the screenshot. The second line of the code was :
Then we put :
So we were working on the method
-(void)flashColor:(UIColor*)color; that you can see in the file SBScreenFlash.h.
Now you can search into the files (the names are really easy to understand, I mean you understand easily what the file do and it’s the same for the metods).
Enjoy jailbreak development.