PhpSnip.com

Star Generator

a class to generate stars given a radius and the amount of points on the star

Info

Source Code ( 123 lines )

<?  

/* ****************************************************
   STAR - class and example to generate a sky of stars
   
   Written By: 	Ronnie Schwartz <ronnie@rustybrick.com>
   				3/2001
   ****************************************************
*/


header("Content-type: image/jpeg");


// CONSTANTS
//
	$AMT_STARS  = 40;			// how many stars do you want
	$APP_WIDTH  = 150;			// width of the applet
	$APP_HEIGHT = 150;			// height of the applet
		
	srand((double)microtime()*1000000);	// init random generator
	
	$im = imagecreate ($APP_WIDTH, $APP_HEIGHT);
	
	$black = ImageColorAllocate ($im, 0, 0, 0);
	
	ImageRectangle($im, 0, 0, $APP_WIDTH, $APP_HEIGHT, $black); // set the background to black (starfield)
	
	// produce AMT_STARS stars at random locations, sizes and shapes
	//
	for ($x=0; $x<$AMT_STARS; $x++) {
		$x_offset = rand(0,$APP_WIDTH);
		$y_offset = rand(0,$APP_HEIGHT);
		$radius   = rand(1,$APP_WIDTH/10);
		$points   = rand(4,8);
			
		$myStar = new Star($radius,$points);					// init star object
			
		$myStar->generateStar($x_offset,$y_offset,$im);			// generate star
	}
	
	ImageJpeg($im,'',100);






//***********************************************************************//
// Star - used to generate a star, given the radius and amount of points //
//***********************************************************************//
class Star
{
	var $radius;		// radius of the star
	var $amtPoints;		// amount of points
	var $amtSides;		// amount of sides (points * 2)


	// Constructor - sets the radius, amtPoints and amtSides variables
	//
	function Star($r, $n)
	{
		$this->radius = $r;
		$this->amtPoints = $n;
		$this->amtSides = $this->amtPoints * 2;
	}
	
	// Generates a star given the location of the star and the graphics object to paint on
	//
	function generateStar($x_offset, $y_offset, &$img)
	{
		$pointA=0;		// used to count the point number from 0 to amtPoints-1 - for outside points
		$pointB=0;		// used to count the point number from 0 to amtPoints-1 - for inside points
	    
		for ($i=0; $i<$this->amtSides; $i++) {
			if ($i % 2 == 0) {														// even = outside points
				$x_coords[$i] = $this->getX($this->amtPoints, $pointA, $this->radius, $x_offset, 0.0);
				$y_coords[$i] = $this->getY($this->amtPoints, $pointA, $this->radius, $y_offset, 0.0);
				$pointA++;
			}
			else {																	// odd = inside points
				$x_coords[$i] = $this->getX($this->amtPoints, $pointB, $this->radius/2, ($this->radius/2) + $x_offset, 0.5);
				$y_coords[$i] = $this->getY($this->amtPoints, $pointB, $this->radius/2, ($this->radius/2) + $y_offset, 0.5);
				$pointB++;
			}
		}
		
		// merge the x_coords and y_coords array into one
		$point = 0;
		for ($i=0; $i<$this->amtSides*2; $i+=2) {
			$coords[$i] = $x_coords[$point];
			$coords[$i+1] = $y_coords[$point];
			
			$point++;
		}
		
		$white = ImageColorAllocate ($img, 255, 255, 255);  			// set stars color to white
		imageFilledPolygon($img, $coords, $this->amtSides, $white);		// paint the star
	}
	
	// Two methods that get the x and y coordinates of a circle given the following information:
	//	 totalPoints - the total amount of points to generate on a circumference
	//	 pointNum	- the number of the point you want to get (0 to totalPoints-1)
	//	 radius		- the radius of the circle
	//	 offset		- the amount of pixels the point should be offset
	//   rotate		- the amount to rotate the circle (needed to draw inner circle and make star)
	
	//	getX - generates x coordinates using cos()
	function getX($totalPoints, $pointNum, $radius, $offset, $rotate)
	{
		$PI = 3.14;
		return (int) (cos( 2 * $PI * ($pointNum + $rotate) / $totalPoints) * $radius ) + $radius + $offset;
	}
	
	//	getY - generates y coordinates using sin()
	function getY($totalPoints, $pointNum, $radius, $offset, $rotate)
	{
		$PI = 3.14;
		return (int) (sin( 2 * $PI * ($pointNum + $rotate) / $totalPoints) * $radius ) + $radius + $offset;
	}
}

?>