triangle.php

<?php
//sherpinski triangle fractal generator for PHP
//Copyright (C)2015 FutureSight Technologies - all rights reserved, do not copy
$iterations = input('Iterations?');;
$squaresize = input('Size?');

function input($prompt) {
	echo $prompt . ' ';
	$line = fgets(STDIN);
	return (int)strtok($line, "\n");
}

function drawtriangle($vertex1, $vertex2, $vertex3) {
	global $image, $black;
	imageline($image, $vertex1[0], $vertex1[1], $vertex2[0], $vertex2[1], $black);
	imageline($image, $vertex2[0], $vertex2[1], $vertex3[0], $vertex3[1], $black);
	imageline($image, $vertex3[0], $vertex3[1], $vertex1[0], $vertex1[1], $black);
}

$image = imagecreate($squaresize, $squaresize * sqrt(3) / 2);
imagecolorallocate($image, 255, 255, 255); //change to adjust background color

$black = imagecolorallocate($image, 0, 0, 0); //change to adjust line color

//draw original triangle
drawtriangle(array(0, $squaresize * sqrt(3) / 2), array($squaresize, $squaresize * sqrt(3) / 2), array($squaresize / 2, 0));
$triangles = array(
	0 => array(
		array(
			array(0, $squaresize * sqrt(3) / 2), array($squaresize, $squaresize * sqrt(3) / 2), array($squaresize / 2, 0)
		)
	)
);

//draw triangle at midpoints
for ($i = 0; $i < $iterations; $i++) {
	$newrow = array();
	$triangleset = $triangles[$i];
	$iterationstart = microtime();
	echo 'Starting iteration ' . ($i + 1);
	foreach ($triangleset as $triangle) {
		//for each triangle, draw 3 more
		$a = $triangle[0];
		$c = $triangle[1];
		$e = $triangle[2];
		
		$b = array(($triangle[0][0] + $triangle[1][0]) / 2, ($triangle[0][1] + $triangle[1][1]) / 2);
		$d = array(($triangle[1][0] + $triangle[2][0]) / 2, ($triangle[1][1] + $triangle[2][1]) / 2);
		$f = array(($triangle[2][0] + $triangle[0][0]) / 2, ($triangle[2][1] + $triangle[0][1]) / 2);
		drawtriangle($b, $d, $f);
		
		$newrow[] = array($a, $b, $f);
		$newrow[] = array($b, $c, $d);
		$newrow[] = array($d, $e, $f);
	}
	$triangles[] = $newrow;
	unset($triangles[$i]);
	echo ' ... completed (' . ((microtime() - $iterationstart) * 1000) . ' milliseconds)' . "\n";
}
echo 'Saving image (this may take a while)...' . "\n";
imagepng($image, 'out.png');
system('out.png');