November 28
Lesson 10: Sprite Color
Source code for this lesson completed: http://www.bluerosegames.com/brg/XnaLesson10.zip
So far, when drawing the sprites we've been using Color.White as the color to draw with. Color.White will preserve the original color of the sprite, but we can get some interesting effects by using other colors.
In order to allow each BouncingBall sprite to have its own drawing color, let's add a DrawingColor Property to the BouncingBall class and an associated private field _drawingColor to store the color. The code will look something like this:
private Color _drawingColor;
public Color DrawingColor
{
get { return _drawingColor; }
set { _drawingColor = value; }
}
Here's a tip. Instead of typing all that in, put the cursor where you want the Field and Property definitions to be, and type the word prop and hit the Tab key twice. Then tab to each green area and type in the appropriate information. The property definition will be updated appropriately. In the BouncingBall constructor, add the following line to initialize the value in _drawingColor:
_drawingColor = Color.White;
So if we don't set the drawing color to something else, it will default to white.
Now change the BouncingBall.Draw() method to use this color instead of Color.White. The method will now look like this:
public void Draw(SpriteBatch spriteBatch)
{
spriteBatch.Draw(Texture, _position, _drawingColor);
}
So again the Game1 class is simplified and more logic is put in the BouncingBall class. Now imagine that we have another sprite class that does something completely different than the BouncingBall class. We could still have the same Draw() and Update() methods, and call them exactly the same way from the Game1 class, and do two totally different things.
So now if you run the program again, it does the same thing as always. Now for something completely different. Add the following image to your project by saving it to your computer and then using the "Add Existing Item" dialog. It should be called white_ball.png.
In the Game1.LoadGraphicsContent() method, change red_ball to white_ball. Then after the ball2.Velocity = new Vector2(10f, 5f);
statement, add the following:
ball2.DrawingColor = Color.Purple;
Now if you run the program again, you should have a white ball and a purple ball. Colors can also be specified as a combination of Red, Green and Blue. Pretty much any color can be represented by the correct combination of red, green, and blue. So you can change the above line to:
ball2.DrawingColor = new Color(255, 0, 255);
Where the first argument is the amount of red the color will have, with 255 being the maximum and 0 being the minimum. The second argument is the amount of green for the color, and the last is the amount of blue. So this color will be full red, no green, and full blue. When referring to colors in computer programming, especially in web design, we often refer to the RGB value of a color (short for Red, Green Blue). Run the program again. The ball should now be a bright purple.
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