Hey, I am looking to implement some collision detection for my 2d "engine". I came across collision masks while googling. It seems like a really good idea, the problem is, I do not fully understand how to make/implement it. This is what I understand so far:
1. I create my level using paint or whatever.
2. Then what I do is create a new layer, and draw for example, a straight black rectangle over the ground. I then delete the original level layer so I am just left with the black rectangle.
3. Load the map and mask into separate SDL_Surfaces.

But after this is where I do not understand what to do! I have some questions that I would be grateful for an answers:
1. How do I actually test the collision?
2. Do I have to iterate through each pixel in the mask and then check the colour of the pixel?
3. How do I set a different type of collision on a different colour?(I'm guessing I just do some check like: if(pixel is black) COLLISION_TYPE = ground)...but that seems wrong?
4. Do I have to iterate through the entire mask every time through my game loop? Which would mean iterating through each pixel?
5. How would I apply a mask to a moving surface, such as my player character?

I am sorry for being so noob but this is really hard to understand. Please can somebody try to answer these questions. Thanks