cocos2d iphone - How do I convert the coordinates of a click to a tilemap position?

How do you turn a tilemap (produced by TileD) for cocos2d where I can click on individual items and get a callback?

Is it just a case of converting captured touch and finding out where it is on the tilemap and then converting that to pixels -- but that doesn't say what item was clicked on.

I have a tilemap of a city with buildings on it, and I'd like to be able to click or press on a specific building, get a callback.

What would be the best way to accomplish this?

Answer

I think you're getting your pixel coordinates and tilemap coordinates confused.

Tile coordinates count tiles.

Pixel coordinates count pixels.

To convert from a pixel coordinate to a tile coordinate, divide the click_x by the tile width and the click_y by the and tile height, to get the tile coordinates x and y. (Discard the remainders to get an integer.)

The reason this works is pretty clear if we overlay the two coordinate systems:

In this above case, the pixel coordinates of the click would correspond to 6,4 in tile coordinates.

Once you know what tile position a click corresponds to, it should be trivial to find the contents of that tile.