Setting a Color Value in .NET framework

Generation QR Code ISO/IEC18004 in .NET framework Setting a Color Value

You now have a variable that can hold the color of your background. At the moment, it is not set to anything useful. So next, you have to write a statement that causes the game program to put a value into this variable. You start by creating a new Color value that contains a

particular amount of red, blue, and green. Figure 2-4 shows the anatomy of an assignment that makes a new Color value and then places it in the variable.

new Color (0,0,0);

The thing that is going to be assigned is on the right side of the equals sign. In this case, you are making a new Color value. Don t get this confused with a double-equals that might be used to compare two things. You should regard the equals sign in Figure 2-4 as being what I call a gozzinta operator. The value on the right of the equals sign goes into the variable on the left. You will investigate how to compare things later in this chapter, in the section Making a Proper Mood Light. Now that you have your variable, you can use it in the game program:

GraphicsDevice.Clear(backgroundColor);

The preceding statement calls the Clear method and feeds it the value of backgroundColor. This causes the screen to be cleared to the new color you created. If you put these statements together, you get a game program that contains a backgroundColor variable that is used by the Draw method, which sets it to a value and then clears the screen using it:

protected override void Draw(GameTime gameTime) { Color backgroundColor; backgroundColor = new Color(0,0,0); GraphicsDevice.Clear(backgroundColor); base.Draw(gameTime); }

If you want to find out what color you get if you make one with no red, no green, and no blue, you can run a program that uses this Draw method. But I don t think I m giving too much away when I tell you that this would produce a black screen. The actual color values are given in the order red, green, and blue, and each must be in the range 0 to 255 (you shall learn the reason for this later). By using different values when you set the Color, you can experiment with different displays. The color combinations obey all the rules of color combinations (for light, rather than for paint) that you would expect:

backgroundColor = new Color(255, 255, 0);

The preceding statement sets backgroundColor to a color value that has the red and green values at maximum, which would be displayed as yellow.

Background creates a ye ow background co or and fi s the screen w th t You can change the numbers n the Draw method to make any co or you ke

At this point, you can see that we can add C# statements to the Draw method to change what is drawn on the screen. You also know that XNA uses a Color structure to lump together information that describes a particular color and that you can create your own Color variables in the game that contain a specific amount of red, green, and blue. Finally, you have managed to make a program that uses a color variable to set the screen to any color that you like. Next, you want the light to change color over time, to get a nice soothing mood light effect. This sounds like hard work (and like every great programmer, I really hate hard work), but actually it turns out to be quite easy. To discover how to do this, you have to find how XNA is connected to the game programs that you write. The way this works uses C# classes.