Sprite Sheets - Learning C# by Programming Games - page 263

Fig. 19.1 An example of a
sheet of sprites (four columns
and two rows)

LoadContent method, and we add the background sprite to it:

gameWorld = new GameObjectList();
gameWorld.Add( new SpriteGameObject("Sprites/spr_background_levelselect"));

We also add the penguin sprite to the game world, and position it somewhere in the
middle of the screen:

SpriteGameObject penguin = new SpriteGameObject("Sprites/spr_penguin@4x2", 1,
"penguin");

penguin.Position = new Vector2(500, 420);
gameWorld.Add(penguin);

19.3 Loading a Sprite Sheet

In the Jewel Jam game, a SpriteGameObject instance keeps a reference to the sprite,
which is represented by an object of type Texture2D . In order to deal with sprite
sheets, we are going to create a new class called SpriteSheet that we will use instead
of a Texture2D object directly. We will add specific functionality to this class that
allows us to maintain the number of rows and columns in the sheet and that can
select a different element of the sheet to be drawn.
In the previous section, you've probably seen that the name of the penguin sprite
('spr_penguin@4x2') is quite peculiar. The reason is that we are going to add a
nice trick to the SpriteSheet class that allows us to specify in the file name what the
dimensions of the sprite sheet are. In this case, the penguin sprite has four columns
and two rows. The SpriteSheet constructor then analyzes the name of the sprite and
determines the dimensions accordingly. There are three different possibilities:
• the image is a single sprite: in that case, no definition is provided at the end of the

filename, an example is the sprite 'spr_wall.png';

• the image is a strip of sprites: in that case, we provide a single integer number

behind the '@' sign, an example is the sprite '[e-mail]';

• the image is a sheet of sprites: both dimensions (columns times rows) are provided

in the filename, for example in '[e-mail]'.
We are going to use the Split method from the string class to find out which possi-
bility we are dealing with. But before we do that, we need to declare a few member
variables for storing the sheet dimensions and the part of the sprite sheet that is