1. Graphics -- Introduction
The use of graphics is common among modern software systems
Java has strong API support for graphics in the java.awt (abstract windowing toolkit) package

2. The Graphics Class
An object of the Graphics class represents a particular drawing surface
It defines a graphics context in which drawn shapes will be rendered
The Graphics class contains methods for drawing various shapes and controlling visual aspects like font and color
An applet has a graphics context, which is automatically passed to the paint method when it is called

3. The Coordinate System
A simple two-dimensional coordinate system exists for each graphics context (or drawing surface)
Each point on the coordinate system represents a single pixel
The top left corner of the area is coordinate <0, 0>
A drawing surface has a particular width and height
Anything drawn outside of that area will not be visible
See Coordinates.java

4. The Coordinate System X <0, 0> x y <x, y>
<width-1, height-1> x y Y X

5. Color
The Color class is used to define and manage the color in which shapes are drawn
Colors are defined by their RGB value, which defines the relative contribution of the primary colors red, green, and blue
Each drawing surface has a foreground color and a background color
The setColor method of the Graphics class defines the foreground color, and the setBackground method of the component (the applet) sets the background color

6. Color
The Color class contains several predefined colors, defined as public, static constants
See Nature.java
Many other colors can be defined using the constructor of the Color class
Over 16 million colors can be defined, but humans cannot distinguish between many similar colors
Furthermore, the hardware of most systems has limitations to the color options available

7. XOR Mode
Drawing in normal mode causes shapes of the same color to blend together
Drawing in XOR mode causes the overlapping portions of the shapes to be rendered in a contrasting color
This effect can be used to "erase" a shape by redrawing it in the same color in the same spot while in XOR mode
See XOR_Demo.java

8. lines, ovals, rectangles, arcs, polygons, and polylines
Drawing Shapes
The Graphics class contains methods for drawing several specific shapes:
lines, ovals, rectangles, arcs, polygons, and polylines
Most shapes can be drawn filled or unfilled
A line, drawn with the drawLine method, is always one pixel wide and cannot be filled

9. Ovals An oval is defined by its bounding rectangle:
The methods that draw an oval take four parameters, all integers:
drawOval (x, y, width, height)
fillOval (x, y, width, height)
width
height

10. Ovals
The first two parameters are the <x, y> coordinate of the top-left corner of the bounding rectangle
The third and fourth parameters specify the width and height of the bounding rectangle
The drawOval method draws an unfilled oval and the fillOval method draws a filled (opaque) oval
See Ovals.java and Rotating_Disk.java

11. Rectangles Rectangles can be drawn
filled or unfilled
with squared or rounded corners
with a slight three-dimensional effect or not
The primary parameters for all rectangle drawing methods define the upper left corner of the rectangle and its width and height
The shape of the rounded corner of a rounded rectangle are defined by an arc width and height

12. Rectangles
A three dimensional rectangle is shown using a small highlight on two sides of the rectangle
The highlight appears on the bottom and right or the top and left as specified by a boolean parameter to the 3D drawing methods
See Rectangles.java, Rounded_Rectangles.java, and Three_D_Rectangles.java

13. Arcs An arc is defined as a segment of an oval
The first four parameters to the arc drawing methods define the bounding rectangle of the oval (top left corner, width, and height)
The other two parameters define the start angle and the arc angle
The start angle indicates where the arc begins and the arc angle determines how far the arc sweeps across its defining oval
See Arc.java

14. Arcs
The start angle can be specified using both positive and negative values: 90
-270 45
-315
360
-360
270
-90
180
-180

15. Arcs An arc angle can also be positive or negative
A positive arc angle sweeps counterclockwise, and a negative arc angle sweeps clockwise
Therefore, the same arc can be specified using four different combinations of start and arc angles
Arcs can also be filled or unfilled
See Arcs.java

16. Polygons
A polygon is a multisided figure defined by a series of ordered points
Line segments connecting the points form the polygon
The points are defined by corresponding arrays of x and y coordinate values, and can already be incorporated into an object of the Polygon class
Polygons are closed, forming a line segment from the last point back to the first
See Polygons.java

17. Polylines
A polyline is similar to a polygon except that it is not closed
That is, there is no line segment from the last point back to the first unless explicitly specified
They are convenient for specifying certain kinds of complex shapes
Polylines cannot be filled
See Polylines.java

18. Fonts
A font defines the look of each character when it is printed or drawn
The Font class provides methods for specifying fonts in a Java program
Each computer system supports a specific set of fonts
See Font_Lister.java
The setFont method defines the current font for a program

19. Fonts
A font is defined using the Font class constructor and a combination of:
font name
font style: plain, bold, italic, or bold+italic
font size, in points
Constants are defined in the Font class to specify the font style
See Entropy.java

20. Animations
Simple animations can be accomplished by drawing a shape, then erasing it, then drawing it again in a slightly altered position
Erasing can be accomplished through careful use of XOR mode
Timing must be controlled so that the animation does not move too fast
See Bouncing_Ball.java