<?php
/**
* function gradient
* Copyright (C) 2006 Dao Gottwald
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Contact information:
* Dao Gottwald <dao at design-noir.de>
*
* @version 1.0
*/
function gradient($from, $to, $height, $steps, $step_width) {
$im = imagecreatetruecolor(++$steps * $step_width, $height);
imagesavealpha($im, true);
imagealphablending($im, false);
imagefill($im, 0, 0, imagecolorallocatealpha($im, 225, 225, 225, 127));
$from = explode(',', $from);
$to = explode(',', $to);
$diff = array();
for ($i = 0; $i < 4; $i++) {
$diff[$i] = ($from[$i] - $to[$i]) / $steps;
}
for ($step = 0; $step < $steps; $step++) {
for ($i = 0; $i < 4; $i++) {
$rgb[$i] = round($from[$i] - $diff[$i] * $step);
if ($i < 3) {
if ($rgb[$i] > 255) {
$rgb[$i] = 255;
}
} elseif ($rgb[3] > 127) {
$rgb[3] = 127;
}
}
$col = imagecolorallocatealpha($im, $rgb[0], $rgb[1], $rgb[2], $rgb[3]);
imagefilledrectangle($im, $step * $step_width, 0, ($step + 1) * $step_width - 1, $height, $col);
}
header('Content-type: image/png');
imagepng($im);
imagedestroy($im);
}
orange_to_black-opaque_to_transparent.php
<?php
require_once 'gradient.php';
$from = '255,180,60,0';
$to = '0,0,0,127';
$height = 50;
$steps = 255;
$step_width = 3;
gradient ($from, $to, $height, $steps, $step_width);
<?php
if (isset($_POST['from'])
&& isset($_POST['to'])
&& isset($_POST['height'])
&& isset($_POST['steps'])
&& isset($_POST['step_width'])
&& preg_match('~^\d{1,3},\d{1,3},\d{1,3},\d{1,3}$~', $_POST['from'])
&& preg_match('~^\d{1,3},\d{1,3},\d{1,3},\d{1,3}$~', $_POST['to'])
&& preg_match('~^[1-9]\d{0,2}$~', $_POST['height'])
&& preg_match('~^[0-2]\d{0,2}$~', $_POST['steps'])
&& preg_match('~^[1-5]$~', $_POST['step_width'])) {
require_once 'gradient.php';
gradient($_POST['from'], $_POST['to'], $_POST['height'], $_POST['steps'], $_POST['step_width']);
exit;
}
?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="de" lang="de">
<head>
<title>Farbverlauf</title>
</head>
<body>
<h1>Farbverlauf</h1>
<form action="" method="post">
<fieldset>
<legend>Optionen</legend>
<ul>
<li>
<label><input type="text" name="from" value="255,180,60,0"/> RGBA-Farbwert 1<br/>
Rot,Grün,Blau,Alpha (0–255,0–255,0–255,0–127)</label>
</li>
<li>
<label><input type="text" name="to" value="0,0,0,127"/> RGBA-Farbwert 2<br/>
Rot,Grün,Blau,Alpha (0–255,0–255,0–255,0–127)</label>
</li>
<li>
<label><input type="text" name="height" value="50"/> Höhe<br/>
Pixel (1–999)</label>
</li>
<li>
<label><input type="text" name="steps" value="255"/> Abstufungen<br/>
(0–255)</label>
</li>
<li>
<label><input type="text" name="step_width" value="3"/> Breite einer Stufe<br/>
Pixel (1–5)</label>
</li>
</ul>
</fieldset>
<p>
<input type="submit"/>
</p>
</form>
</body>
</html>
