USING COLORS WITH THE STANDARD GRAPHICS LIBRARY

Built-in colors. The simplest way to specify colors using standard draw is via a list of predefined colors. You can set the foreground color to blue with:

StdDraw.setPenColor(StdDraw.BLUE);

StdDraw.clear(StdDraw.LIGHT_GRAY);

StdDraw.BLACK
StdDraw.BLUE
StdDraw.CYAN
StdDraw.DARK_GRAY
StdDraw.GRAY
StdDraw.GREEN
StdDraw.LIGHT_GRAY
StdDraw.MAGENTA
StdDraw.ORANGE
StdDraw.PINK
StdDraw.RED
StdDraw.WHITE
StdDraw.YELLOW

User-defined colors. The Java class Color allows you to construct your own colors using RGB or HSB formats. For complete details check out the Java Color API. Unless you have extreme needs, the following examples will probably suffice: (We'll introduce classes in Section 3.1.) To access the Color class, you need to include the following statement at the beginning of your Java program:

import java.awt.Color

• RGB format. RGB format specifies a color by three integer values between 0 and 255, representing the combination of red, green, and blue in the color. This format is commonly used in television screens, computer monitors, digital cameras, and web pages. (The primary color green is used instead of yellow because yellow phosphors are much more expensive to produce.) You can create your own colors as follows:

  StdDraw.setPenColor(new Color(255,   0,   0));   // red
  StdDraw.setPenColor(new Color(  0, 255,   0));   // green
  StdDraw.setPenColor(new Color(  0,   0, 255));   // blue
  StdDraw.setPenColor(new Color(255, 255,   0));   // yellow
  StdDraw.setPenColor(new Color(255, 255, 255));   // white
  StdDraw.setPenColor(new Color(  0,   0,   0));   // black
  StdDraw.setPenColor(new Color(100, 100, 100));   // gray
  

  Note that if all three arguments are the same, you get a shade of gray. Web pages typically specify the colors in RGB format, but as a 24-bit hexadecimal integer. You can achieve the same effect in Java.

  StdDraw.setPenColor(Color.decode("#00ffff"));    // cyan
  

• HSB format. HSB format specifies a color by three real values between 0.0 and 1.0, representing the hue, saturation, and brightness. The hue determines the color (from red to orange, yellow, green, blue, indigo, and violet). The brightness determines the intensity (from light or dark). The saturation determines the color depth (from dull to intense). This format roughly corresponding to the way in which the human eye perceives color. You can achieve a nice rainbow effect by varying the hue, while holding the saturation and brightness at 1.0. This can be useful for visualizing scientific data. For example, if you are plotting the movement of a particle over time, you might plot the particle in a different color at each time step.

  for (int i = 0; i < 256; i++) {
      StdDraw.setPenColor(Color.getHSBColor(i / 256.0f, 1.0f, 1.0f));
      // plot something
  }
  

  The three input parameters to Color.getHSBColor are of real numbers of type float - this is why you need to use 1.0f instead of 1.0. It's also can be fun to generate random colors. The following code fragment generates a random color from the rainbow.

  StdDraw.setPenColor(Color.getHSBColor((float) Math.random(), .8f, .8f));