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<?php
/*
* $Id: gradient.php,v 1.3 2004/11/29 10:18:17 musus Exp $
*
* Description:
* Generate a gradient image for use as a background image.
* Required gd module.
*
* Input Parameters:
* height - Height of output image (width is 1)
* colors - Number of colors to generate
* base - Base color specified as "base=FFC0C0" or "base=#FFC0C0"
*
* Security:
* No security restrictions by user.
* Limit height parameter to 600.
*/
$MAX_HEIGHT = 600;
$MIN_COLORS = 4;
$MAX_COLORS = 256;
$DEFAULT_COLORS = 32;
$PERCENT = 15; // Percent to change brightness
$width = 5; // could be 1, doesn't really matter since browser will stretch it
// Get a value from a GET URL
function getGetValue ( $name ) {
if ( ! empty ( $_GET[$name] ) )
return $_GET[$name];
if ( ! isset ( $HTTP_GET_VARS ) )
return null;
if ( ! isset ( $HTTP_GET_VARS[$name] ) )
return null;
return ( $HTTP_GET_VARS[$name] );
}
// Convert a hex value to an integer
function hextoint ( $val ) {
if ( empty ( $val ) )
return 0;
switch ( strtoupper ( $val ) ) {
case "0": return 0;
case "1": return 1;
case "2": return 2;
case "3": return 3;
case "4": return 4;
case "5": return 5;
case "6": return 6;
case "7": return 7;
case "8": return 8;
case "9": return 9;
case "A": return 10;
case "B": return 11;
case "C": return 12;
case "D": return 13;
case "E": return 14;
case "F": return 15;
}
return 0;
}
$height = getGetValue ( "height" );
if ( empty ( $height ) )
$height = 50;
if ( $height > $MAX_HEIGHT )
$height = $MAX_HEIGHT;
$numcolors = getGetValue ( "colors" );
if ( empty ( $numcolors ) )
$numcolors = $DEFAULT_COLORS;
else {
if ( preg_match ( "/^\d+$/", $numcolors ) ) {
if ( $numcolors < $MIN_COLORS )
$numcolors = $MIN_COLORS;
else if ( $numcolors > $MAX_COLORS )
$numcolors = $MAX_COLORS;
} else {
$numcolors = $DEFAULT_COLORS;
}
}
// Get base color
$red = $green = $blue = 192;
$base = getGetValue ( "base" );
if ( empty ( $base ) )
$base = "C0C0C0";
if ( preg_match ( "/^#(\S+)/", $base, $matches ) ) {
$base = $matches[1];
}
if ( preg_match ( "/^[0-9a-fA-F]+$/", $base ) ) {
// valid color
} else {
// Invalid color
$base = "C0C0C0";
}
if ( strlen ( $base ) == 6 ) {
$red = 16 * hextoint ( substr ( $base, 0, 1 ) ) +
hextoint ( substr ( $base, 1, 1 ) );
$green = 16 * hextoint ( substr ( $base, 2, 1 ) ) +
hextoint ( substr ( $base, 3, 1 ) );
$blue = 16 * hextoint ( substr ( $base, 4, 1 ) ) +
hextoint ( substr ( $base, 5, 1 ) );
} else if ( strlen ( $base ) == 3 ) {
$red = 16 * hextoint ( substr ( $base, 0, 1 ) );
$green = 16 * hextoint ( substr ( $base, 1, 1 ) );
$blue = 16 * hextoint ( substr ( $base, 2, 1 ) );
} else {
// Invalid color specification
}
//echo "Base=$base<br />";
//echo "Red=$red<br />Green=$green<br />Blue=$blue<br />\n"; exit;
$image = imagecreate ( $width, $height );
// Allocate array of colors
$colors = array ();
$delta = 256 * $PERCENT / 100;
$deltared = $deltagreen = $deltablue = $delta;
if ( $red + $deltared > 255 )
$deltared = 255 - $red;
if ( $green + $deltagreen > 255 )
$deltagreen = 255 - $green;
if ( $blue + $deltablue > 255 )
$deltablue = 255 - $blue;
//echo "deltared=$deltared<br />deltagreen=$deltagreen<br />deltablue=$deltablue<br />";
//echo "red=$red<br />green=$green<br />blue=$blue<br />";
for ( $i = 0; $i < $numcolors; $i++ ) {
$thisdelta = ceil ($delta * $i / $numcolors);
//echo "thisdelta=$thisdelta<br />";
$thisred = $red + ( $deltared * $i / $numcolors );
if ( $thisread > 255 )
$thisread = 255;
$thisgreen = $green + ( $deltagreen * $i / $numcolors );
if ( $thisgreen > 255 )
$thisgreen = 255;
$thisblue = $blue + ( $deltablue * $i / $numcolors );
if ( $thisblue > 255 )
$thisblue = 255;
$thisred = floor ( $thisred );
$thisgreen = floor ( $thisgreen );
$thisblue = floor ( $thisblue );
$colors[$i] = imagecolorallocate ( $image, $thisred, $thisgreen, $thisblue );
//echo "Color $i: $thisred $thisgreen $thisblue<br />";
}
for ( $i = 0; $i < $height; $i++ ) {
// Which color for this line?
$ind = floor ( $numcolors * $i / $height );
if ( $ind >= $numcolors )
$ind = $numcolors;
$y = $height - $i - 1;
imageline ( $image, 0, $y, $width - 1, $y,
$colors[$ind] );
//echo "Line $i, color $ind<br />";
}
//exit;
if ( function_exists ( "imagepng" ) ) {
Header ( "Content-type: image/png" );
imagepng ( $image );
} else if ( function_exists ( "imagegif" ) ) {
Header ( "Content-type: image/gif" );
imagegif ( $image );
} else {
echo "No image formats supported!<br />\n";
}
imagedestroy ( $image );
?>
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