GRAPHICS CLASSES

  The AWT supports many graphics methods. All graphics are drawn relative to a window. This can be the main window of an applet, a child window of an applet, or a stand-alone application window. A graphics context is encapsulated by the Graphics Class and it’s obtained two ways:

·         It is passed to an applet when one of its various methods, such as paint() or update(),is called.

·         It is returned by the getGraphics() methods of  component.

  The Graphics class defines a number of drawing function. Each shape can be drawn edge-only or filled. Object are drawn and filled in the currently select graphics color, which is black by default. The several drawing methods :

·         Drawing  Lines: Line are draw by means of the drawline() method:

            void drawLine(int startX,int startY, int endX,endY)

Therefore drawLine() display a line in the current drawing color that beings at  startX startY ends at endX,endY.

· Drawing Rectangles: The drawRect() and fillrect() methods display an outline and filled rectangle, respectively.

            void drawRect(int top,int left,int width,int height)

            void fillRect(int top,int left,int width,int height)

The upper–left corner of the rectangle is at top, left. The dimensions of the rectangle are specified by width and height. To draw a rounded rectangle, use drawRoundRect() and fillRoundRect(), both  are shown here:

            void fillRoundRect(int top,int left,int width,int height,int xDiam,int yDim)

A rounded rectangle has rounded corners; the upper left corner of the rectangle is at top, left. The dimension of the rectangle is specified by width and height.  

· Drawing Ellipses and Circle: To draw an ellipse, use drawOval(). To fill an ellipse, use fillOval(). These methods are shown here:

            void drawOval(int top,int left,int width,int height)

            void fillOval(int top,int left,int width,int height)

The ellipse is drawn within a bounding rectangle whose upper–left corner is specified by top, left and whose width and height are specified by width and height.

· Drawing polygon:  It is possible to draw arbitrarily shaped figures using drawPolygon().

            void drawPolygon(int x[],int y[],int numpoints)

            void fillPolygon(int x[],int y[],int numpoints)

The polygon’s endpoints are specified by the coordinate pairs contained within the x and y arrays. The number of points defined by x and y is specified by numpoints. 

  Working with Color: Java supports color in a portable, device-independent fashion. The AWT color system allows you to specify any color you want. The color is supported by various hardware devices. Color is encapsulate by the color class.

Color defines several constants (for example Color.black) to specify a number of common colors. We can also create our own colors, using one of the color constructors.

            Color(int red,int green,int blue)

            Color(int rgbValue)

            Color(float red,float green,float blue)

·         Color Methods: That color class defines several methods that help manipulate colors:

                                                getRed(),getGreen(),getBlue()

We can obtain the red, green, and blue components of a color independently using getRed(), getGreen(), and getBlue() as show here:

                        int getRed()

                        int getGreen()

                        int getBlue()

Each of these methods returns the RGB color component found in the invoking Color object in the lower 8 bit integer.

· Setting the Current Graphics color:  By default, graphics object are drawn in the current foreground color. You can change this color by calling the Graphics method setColor()

            void setColor(Color  newcolor)

            You can obtain the current color by calling getColor() shown here:

Color getColor();