Creating a Negative

$/*$ Method to negate the picture $*/$

public void negate$()\{$

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

Pixel pixel $=$ null;

int redValue, blueValue, greenValue $=0$; for $($int i $=0$; i $<$ pixelArray.length; i$++)$

$\{$ pixel pixelArray$[$i$]$;

redValue $=$ pixel.getRed$()$;

greenValue $=$ pixel.getGreen$()$;

blueValue pixel.getBlue$()$;

pixel.setColor$($new Color$(255-$ redValue, $255-$ greenValue, $255-$

$\}$ blueValue$))$;

$\}$

$\}$

explain the code kindly