How to convert coordinates between world coordinates and screen coordinates

Question

I am using a tilemap in which I have square tiles.
Knowing that, the size of the screen and the player position(in world coordinates) how I convert between this systems? Is there any formula?

EDIT:
For example:

The top left corner is (0,0)
player position in tiles: (ScreenX / 2, ScreenY / 2)
player position in screen: always (0, 0)
grass tile position in tiles: (Gx, Gy)

Now the question is: how can I get the screen coordinates for the grass tile?

Answer 1

If your grass tile's position in the tilemap is <Gx,Gy> then its pixel position in the game world will be:

tile_worldX = Gx * Tile_Size
tile_worldY = Gy * Tile_Size

Then you subtract the position of the screen's top-left corner from these coordinates to get their on-screen pixel position:

tile_screenX = tile_worldX - view_x
tile_screenY = tile_worldY - view_y

This assumes that the screen's top-left corner is 0,0 in your viewport. Sometimes game engines will move 0,0 to the middle or bottom-left of the viewport so you may have to compensate for that difference.