<?php
/***************************************************************************************
 * Script for automatic generation of one pixel
 * alpha-transparent images for non-RGBA browsers.
 * @author Lea Verou
 * @version 1.2
 * Licensed under the MIT license (http://www.opensource.org/licenses/mit-license.php)
 ***************************************************************************************/

######## SETTINGS ##############################################################

/**
 * Enter the directory in which to store cached color images.
 * This should be relative and SHOULD contain a trailing slash.
 * The directory you specify should exist and be writeable (usually chmoded to 777).
 * If you want to store the pngs at the same directory, leave blank ('').
 */
define('COLORDIR', 'colors/');


/**
 * If you frequently use a color with varying alphas, you can name it
 * below, to save you some typing and make your CSS easier too.
 *
 * By default, the 16 valid HTML color names are included.
 */
$color_names = array(
	'aqua'    => array(0, 255, 255),
	'black'   => array(0, 0, 0),
	'blue'    => array(0, 0, 255),
	'fuchsia' => array(255, 0, 255),
	'gray'    => array(128, 128, 128),
	'green'   => array(0, 128, 0),
	'lime'    => array(0, 255, 0),
	'maroon'  => array(128, 0, 0),
	'navy'    => array(0, 0, 128),
	'olive'   => array(128, 128, 0),
	'purple'  => array(128, 0, 128),
	'red'     => array(255, 0, 0),
	'silver'  => array(192, 192, 192),
	'teal'    => array(0, 128, 128),
	'white'   => array(255, 255, 255),
	'yellow'  => array(255, 255, 0)
);

/**
 * If you want the generated image to have a greater or smaller size than 10x10, you may adjust the following.
 * Apart from debugging purposes (it's easier to see if the image has a problem when it's something
 * large), some people argue that the browser needs to spend substantially more resources
 * to render the background when the image is too small (like 1x1).
 */
define('SIZE', 10);

/**
 * If you don't want the generated pngs to be cached on the server, set the following to
 * false. This is STRONGLY NOT RECOMMENDED. It's here only for testing/debugging purposes.
 */
define('CACHEPNGS', true);

######## NO FURTHER EDITING, UNLESS YOU REALLY KNOW WHAT YOU'RE DOING ##########

// Only report errors that would stop the script anyway, since the output is an image so even an
// extra byte will prevent it from showing up
error_reporting(E_ERROR | E_PARSE);

$dir = substr(COLORDIR, 0, strlen(COLORDIR) - 1);

if (!is_writable($dir)) {
	die("The directory '$dir' either doesn't exist or isn't writable.");
}

// Are the RGB values provided directly or implied through a named color?
if (isset($color_names[$_REQUEST['name']])) {
	list($red, $green, $blue) = $color_names[$_REQUEST['name']];
	$alpha = $_REQUEST['a'] / 100;
}
else {
	if(isset($_REQUEST['r']) and isset($_REQUEST['g']) and isset($_REQUEST['b'])) {
		// Old way: rgba.php?r=R&g=G&b=B&a=100*A
		$color_info = $_REQUEST;
		$alpha = $_REQUEST['a'] / 100;
	}
	else {
		$color_array = explode(',', $_SERVER['PATH_INFO']);
		if (count($color_array) == 2) {
			// New way for names: rgba.php/colorname,alpha
			if (isset($color_names[$color_array[0]])) {
				$color_info = $color_names[$color_array[0]];
				$color_info[] = floatval($color_array[1]);
			} else {
				die("Color name {$color_array[0]} unknown.");
			}
		} else {
			// New way: rgba.php/rgba(R,G,B,A)
			$color_info = explode(',', str_replace(' ', '', substr($_SERVER['PATH_INFO'], 6, -1)));
			$color_info = array_combine(array('r','g','b','a'), $color_info);
			$alpha	= floatval($color_info['a']);
		}
	}
	
	$red	= intval($color_info['r']);
	$green	= intval($color_info['g']);
	$blue	= intval($color_info['b']);
}

// "A value between 0 and 127. 0 indicates completely opaque while 127 indicates completely transparent."
// http://www.php.net/manual/en/function.imagecolorallocatealpha.php
$alpha = intval(127 - 127 * $alpha);

// Send headers
header('Content-type: image/png');
header('Expires: 01 Jan '.(date('Y') + 10).' 00:00:00 GMT');
header('Cache-control: max-age=2903040000');

// Does it already exist?
$filepath = COLORDIR . "color_r{$red}_g{$green}_b{$blue}_a$alpha.png";

if(CACHEPNGS and file_exists($filepath)) {

	// The file exists, is it cached by the browser?
	if (function_exists('apache_request_headers')) {
		$headers = apache_request_headers();

		// We don't need to check if it was actually modified since then as it never changes.
		$responsecode = isset($headers['If-Modified-Since'])? 304 : 200;
	}
	else {
		$responsecode = 200;
	}

	header('Last-Modified: ' . gmdate('D, d M Y H:i:s', filemtime($filepath)) . ' GMT', true, $responsecode);

	if ($responsecode == 200) {
		header('Content-Length: '.filesize($filepath));
		die(file_get_contents($filepath));
	}
}
else {
	$img = @imagecreatetruecolor(SIZE, SIZE)
		  or die('Cannot Initialize new GD image stream');

	// This is to allow the final image to have actual transparency
	// http://www.php.net/manual/en/function.imagesavealpha.php
	imagealphablending($img, false);
	imagesavealpha($img, true);

	// Allocate our requested color
	$color = imagecolorallocatealpha($img, $red, $green, $blue, $alpha);

	// Fill the image with it
	imagefill($img, 0, 0, $color);

	// Save the file (if caching is allowed)
	if (CACHEPNGS) {
		// Check PHP version to solve a bug that caused the script to fail on PHP versions < 5.1.7
		if (strnatcmp(phpversion(), '5.1.7') >= 0) {
			imagepng($img, $filepath, 0, NULL);
		}
		else {
			imagepng($img, $filepath);
		}
	}

	// Serve the file
	imagepng($img);

	// Free up memory
	imagedestroy($img);
}

/* End of file rgba.php */