source: trunk/extras/my_themes/images/header-img.php

<?php

$img = 'xpressheader.jpg';

// If we don't have image processing support, redirect.
if ( ! function_exists('imagecreatefromjpeg') )
        die(header("Location: xpressheader.jpg"));

// Assign and validate the color values
$default = false;
$vars = array('upper'=>array('r1', 'g1', 'b1'), 'lower'=>array('r2', 'g2', 'b2'));
foreach ( $vars as $var => $subvars ) {
        if ( isset($_GET[$var]) ) {
                foreach ( $subvars as $index => $subvar ) {
                        $length = strlen($_GET[$var]) / 3;
                        $v = substr($_GET[$var], $index * $length, $length);
                        if ( $length == 1 ) $v = '' . $v . $v;
                        $$subvar = hexdec( $v );
                        if ( $$subvar < 0 || $$subvar > 255 )
                                $default = true;
                }
        } else {
                $default = true;
        }
}

if ( $default )
        list ( $r1, $g1, $b1, $r2, $g2, $b2 ) = array ( 105, 174, 231, 65, 128, 182 );

// Create the image
$im = imagecreatefromjpeg($img);

// Get the background color, define the rectangle height
$white = imagecolorat( $im, 15, 15 );
$h = 84;

// Define the boundaries of the rounded edges ( y => array ( x1, x2 ) )
$corners = array(
        0 => array ( 25, 734 ),
        1 => array ( 23, 736 ),
        2 => array ( 22, 737 ),
        3 => array ( 21, 738 ),
        4 => array ( 21, 738 ),
        177 => array ( 21, 738 ),
        178 => array ( 21, 738 ),
        179 => array ( 22, 737 ),
        180 => array ( 23, 736 ),
        181 => array ( 25, 734 ),
        );

// Blank out the blue thing
for ( $i = 0; $i < $h; $i++ ) {
        $x1 = 0;
        $x2 = 800;
        imageline( $im, $x1, $i, $x2, $i, $white );
}

// Draw a new color thing
for ( $i = 0; $i < $h; $i++ ) {
        $x1 = 0;
        $x2 = 800;
        $r = ( $r2 - $r1 != 0 ) ? $r1 + ( $r2 - $r1 ) * ( $i / $h ) : $r1;
        $g = ( $g2 - $g1 != 0 ) ? $g1 + ( $g2 - $g1 ) * ( $i / $h ) : $g1;
        $b = ( $b2 - $b1 != 0 ) ? $b1 + ( $b2 - $b1 ) * ( $i / $h ) : $b1;
        $color = imagecolorallocate( $im, $r, $g, $b );
//      if ( array_key_exists($i, $corners) ) {
//              imageline( $im, $x1, 18 + $i, $x2, 18 + $i, $white );
//              list ( $x1, $x2 ) = $corners[$i];
//      }
        imageline( $im, $x1, $i, $x2, $i, $color );
}

//die;
header("Content-Type: image/jpeg");
imagejpeg($im, '', 92);
imagedestroy($im);
?>