Summary: GUI Graphics
Posted on: July 27, 2006 at 12:00 AM
Posted on: July 27, 2006 at 12:00 AM
This is a summary of simple graphics methods in the java.awt.Graphics class.
Example:
Java: Summary: GUI Graphics
This is a summary of simple graphics methods in the java.awt.Graphics class for drawing with shapes, colors,
text, ... Other classes define more advanced graphics, eg, javax.swing.Graphics2D.
java.awt.Graphics Class
Draw on a JPanel. Assume g is a Graphics
object, and all variables are type int unless otherwise declared.
Angles (int startAngle, arcAngle) are in degrees counterclockwise from 3 o'clock.
These methods use (x,y) at the top, left, corner and a width and height of
the bounding box (except drawString, drawLine).
void g.drawLine(x1, y1, x2, y2); void g.drawRect(x, y, width, height); // (x,y) is upper left corner void g.fillRect(x, y, width, height); void g.drawOval(x, y, width, height); void g.fillOval(x, y, width, height); void g.drawArc( x, y, width, height, startAngle, arcAngle); void g.fillArc( x, y, width, height, startAngle, arcAngle); void g.setFont(Font f); // all drawing after this uses the Font f. void g.drawString(String s, x, y); // draws s with the left base at (x,y) void g.drawPolyline(int[] xPoints, int[] yPoints, nPoints); // draws line void g.drawPolygon( int[] xPoints, int[] yPoints, nPoints); // draws polygon void g.drawPolygon( poly); // draws polygon, same for fillPolygon. void g.fillPolygon( int[] xPoints, int[] yPoints, nPoints); // fills polygon void g.setColor(Color c); // all drawing after this uses the Color c. |
Extend (subclass) JPanel for drawing
Drawing is usually done by defining a subclass of JPanel and overriding the paintComponent method.
class MyDrawing extends JPanel {
public MyDrawing() { // constructor
setBackground(Color.WHITE);
}
public void paintComponent(Graphics g) {
super.paintComponent(g); // paint background, borders
g.drawOval(0,0, 100, 100); // do your drawing here.
}
}
java.awt.Polygon
Straight-sided shapes (eg, triangles) can be created with Polygon class and the Graphics drawPolygon or fillPolygon methods.Polygon poly = new Polygon(); // declare and create poly.add(x, y); // add points to polygon g.drawPolygon(poly);The polygon coordinates can be translated with:
poly.translate(deltaX, deltaY);There is also a Polygon constructor which takes arrays of points:
Polygon p = new Polygon(int[] xPoints, int[] yPoints, int nPoints);
JPanel methods
These can be used in the constructor or init() to set the initial valuesthis.setBackground(Color c); // Sets the background color this.setForeground(Color c); // Sets the initial pen color.Use the following to get the size of the panel, if necessary.
int w = this.getWidth(); // Width of the JPanel drawing area int h = this.getHeight(); // Height ...
java.awt.Color Class
| Predefined colors (lowercase without underscores for pre-Java 1.4 |
Color.BLACK,
Color.WHITE,
Color.DARK_GRAY, Color.GRAY, Color.LIGHT_GRAY,
Color.BLUE,
Color.CYAN,
Color.GREEN,
Color.RED,
Color.MAGENTA,
Color.PINK,
Color.ORANGE,
Color.YELLOW,
Color.BLUE,
Color.CYAN
|
| Creating a color |
c = new Color(int r, int g, int b); // creates a new color with RGB values (each 0-255)
Example: Color medblu = new Color(128, 128, 255);
|
java.awt.Font Class to create generic fonts
In addition to the generic fonts below, you can use any of the fonts installed on the system. Get the list of available fonts using (GraphicsEnvironment.getLocalGraphicsEnvironment().getAvailableFontFamilyNames() which returns a String[]). Graphics getFontMetrics() returns info about font measurements.Font f; f = new Font(String name, int style, int size); // creates a new fontname is "Serif", "SansSerif", or "Monospaced", or a font on the system. style is Font.PLAIN. Font.BOLD, Font.ITALIC, or Font.BOLD+Font.ITALIC. size is the point size, usually in the range 8-48.
Example:
Font big = new Font("SansSerif", Font.Bold, 48);
. . .
g.setFont(big);
g.drawString("Greetings Earthling");