Java GRAPHICS

The first step in making graphics shapes in Java is to set the color. After that you can draw the shape and then you must select another color to draw any further shapes of a different color. Basic shapes include rectangles and circles.

Selecting a color

Colors are selected by using the setColor method. Its basic form is :

	setColor(color) ;

Look in the JUDO help files for a list of usable colors. Some are : red orange yellow green blue purple black white etc..
To change color for a shape just call the setColor method before drawing the shape.
The formula for setting the Background Color is:,/p>

		setBackgroundColor(color) ;

Do it now !

	void main() 	{

		setBackgroundColor(black) ;

	}

Drawing Shapes using Java

All the shapes require pixel co-ordinates to create their size and position relative to the window they are drawn in. These are created according to their x, y positions.

To draw a rectangle, you will need to give the top-left x and y points and the width and height .
To draw a rectangle at position (x,y ), you would use the formula :

	drawRectangle(x , y , width , height);

	

Note that the x, y co-ordinates are the top-left corner. All numbers must be int's.
To draw a rectangle at position (100,100) , 200 pixels wide and 200 pixels high, you would use the code:

	drawRectangle(100,100, 200,200);

	void main() 	{

			setBackgroundColor(red);

			setColor(blue);

			drawRectangle(100,100,300,150);

			}

Here is what you should get . Amazing !

Try a circle ! Here is the template, where x, y are the top-left co-ordinates:

	drawCircle( x, y, radius)

Exercise:
Draw a green circle with top-left at (100, 200) and a radius of 50. what is the code for it ?
Answer:

		setColor(green);

		drawCircle(100,200,50);

Notice that the shapes that we have drawn are only outlines and are not filled in. To draw filled shapes use :

	fillRectangle(x, y, width, height);

	fillCircle(x, y, radius);

	fillOval(x, y, width, height);

Lets draw a self portrait !

		void main()	{

			setBackgroundColor(yellow);

			// body

			setColor(red);

			fillRectangle(100,100,50,50);

			// arms

			setColor(green);

			fillRectangle(25,100,75,10);

			fillRectangle(150, 100,75,10);

			// legs

			fillRectangle(100,150,10,75);

			fillRectangle(140,150,10,75);

			// head

			setColor(blue);

			fillCircle(100,50,50);

		}

Output !

 

 

Java drawString method

drawString paints a string of text at the point given.
Here is the template, where String is the text to be written and x, y the coordinates of the bottom-left of the text:

	drawString(String , x , y );

e.g. # 1

		 String name = "Steve";

	 	drawString(name, 35, 25);

	 	

e.g. #2

	drawString("This is text", 15, 35);

Sooo, Lets make our logo:

	void main() 	{

			setBackgroundColor(white);

			setColor(black);

			fillRectangle(100,100,100,100);

			setColor(white);

			drawString("Java For Kids" , 150,120);

			setColor(red);

			drawRectangle(100,100,100,100);

	}

Java Exercises:

1. Draw a line of circles.Use a for loop. Hint , use :
   getDrawingHeight() Returns the height of the drawing area or the window
   getDrawingWidth() Returns the width of the drawing area or window
   Here may be an algorithm u could use:
   

   	// declare width , height of window
   
   	// declare number of circles in a row
   
   	// get width and height of window
   
   	// divide width by number of circles you want =  radius x 2
   
   	// loop for number of  circles
   
   	// draw a circle at count * radius
   
   	//end loop
   
   

   Cut and paste the above algorithm into JUDO and use it as a plan for your program.
   Fill in the code after each comment..
   How would you fill the whole window with circles ?
   Hint - use a for loop inside a for loop. Try it !
   I encourage you to get it totally wrong and pull your hair out.
   
2. a. draw a series of concentric circles . b. a series of concentric rectangles.

Some Answers
house

void main()	{

	setBackgroundColor(black);

	setColor(white);

	// front

	fillRectangle(100,100,300,100);

	// roof

	drawLine(100,100,250,25);

	drawLine(250,25,400,100);

	// windows

	setColor(blue);

	fillRectangle(125,125,20,20);

	fillRectangle(355,125,20,20);

	// door

	setColor(red);

	fillRectangle(240,150, 30,50);

}

Row of Circles

void main()	{

// declare width , height of window

int width;

int height;

int gap;

// declare number of circles in a row

int cnum = 40;

// get width and height of window

width = getDrawingWidth();
// divide width by number of circles you want =  radius x 2

gap = width/cnum;

// loop for number of  circles

for(int counter = 0; counter < cnum ; counter++)

{

	// draw a circle at count * radius

	setColor(red);

	fillCircle(counter*gap,0,gap);

//end loop

}

}