MODIFYING PICTURES USING LOOPS

A monitor with 640 by 480 has 307200 pixels

640 X  480 =  307200 pixels

(H)       (V)

A pixel has three colors r, g, and b

• Each color has three bits
• Values from 0 to 255
• 2^8 = 256 different color intensities
• 256 X 256 X 256 = _______ colors

Java Color class

import java.awt.Color;    //need to import this library abstract Windows ToolKit

Color newColor = new Color (  255, 0, 0)
System.out.println(newColor); // Red = 255 , Green =0 Blue =0

Picture class 

Image file extensions are  bmp, jpg or gif. 

Example display a picture or an image

>String filename= FileChooser.pickAFile( );
>Picture picObject = new Picture ( filename);
> picObject show( ); 

Object methods of the Picture class

            show( )

            explore ( )

            getWidth( )

            getHeight ( )

            getPixel ( )

            getPixels ( )

Pixel class

Picture picObj = new Picture( “c:/A/happy.gif”);

            Pixel pixelObj = picObj.getPixel (0, 0) ;

System.out.println( pixelObj);     //Pixel Red= 140 Green= 80 Blue = 250 

int red;

red = pixelObj.getRed ( ) ;

System.out.println ( red) ;  // 140

red= (int) ( red * 0.5) ;

pixelObject.setRed (red);

 System.out.println(pixelObject.getRed ( ));  //70

Object methods of class Pixel 

getRed ( )

getBlue ( )

getGreen ( )

setRed ( )

setBlue ( )

setGreen ( )

setColor( )

Example

Picture picObject = new Picture ( “C:/A/happy.gif”);

Pixel [ ] pixelArray = picObject.getPixels ( );

System.out.println( pixelArray [0].getBlue ( ));

Example:
Creating a method called decreaseRed in the Picture class

public void decreaseRed ( )

{ Pixel [ ] pixelArray = this.getPixels ( );

Pixel pixelObject = null;

int redvalue;

for ( int i= 0; i <pixelArray.length ; i = i +1 )

{pixelObject = pixelArray [i] ;

redvalue = pixelObject.getRed();

redvalue= (int) (redvalue *0.6) ;

pixelObject.setRed ( redvalue) ;

}

}

Calling the method decreaseRed

Ø      Picture picObject = new Picture ( “C: / happy.gif”);

Ø      picObject.show();

Ø      picObject.decreaseRed ( ) ;

Ø      picObject.repaint ( ) ;

Using loop to solve pixel problems

In the Picture class, create a method named decreaseRed. Pass an amount of decreasing red to the method.
Call the method decreaseRed in the main METHOD . 

      String filename = “C:/A/happy.gif”;
      Picture picObj = new Picture (filename);
      picObj.show( );
      picObj.decreaseRed ( 0.7);
     picObj.repaint ( );

In the Picture class create the Method decreaseRed

- use a for- each loop

public void decreaseRed  (double redpct)
{ int value = 0;
  Pixel [] pixelArray = this.getPixels ( );
             for( Pixel pixelObj : pixelArray)
                 { value = pixelObj.getRed ( );
                   value = (int )(value * redpct);
                    pixelObj.setRed( value);
                 } // Close for loop
} // Close Method

- use a while loop

public void  decreaseRed ( double redpct)
{  Pixel [] pixelArray = this.getPixels( ); |
    Pixel pixelObj  = null;
         int value = 0;
         int i = 0 ;
     while ( i <pixelArray.length)
     { pixelObj = pixelArray [i];
        value = pixelObj.getRed ( );
        value = ( int ) ( value * redpct);
        pixelObj.setRed(value);
        i = i + 1;
      }//Close loop
} // Close Method

- use a for loop

public void decreaseRed ( double redpct )
{ Pixel [ ] pixelArray = this.getPixels ( );
            int value = 0;
            Pixel pixelObj = null ;
        for( i =  0; i = < pixelArray.length; i = i + 1)
          {  pixelObj = pixelArray [i];
             value = pixelObj.getRed ( );
             value = ( int ) ( value * redpct) ;
             pixelObj.setRed ( value ) ;
           } //close loop
}  //close method