<?PHP
error_reporting(E_ALL ^ E_NOTICE);
/*
gradient.php
*/
// convert guaranteed valid hex values to arrays of integers
$foreground = hex2int(validHexColor($_REQUEST['foreground'],'000000'));
$background = hex2int(validHexColor($_REQUEST['background'],'FFFFFF'));
if (isset($_REQUEST['shadow'])) {
// use a middle grey if color is not valid
$shadow = hex2int(validHexColor($_REQUEST['shadow'],'666666'));
} else {
// use a 60% tint of the foreground color if shadow not specified
$shadow = tintOf($foreground,0.6) ;
}
$im = imageCreateFromPNG('gradient.png');
// Get the indicies of Black & White (the 1st & last values in the table)
$black = imageColorResolve($im,0x00,0x00,0x00) ;
$white = imageColorResolve($im,0xFF,0xFF,0xFF) ;
// from the number of colors, calculate distance between each color step
$colorSteps = imageColorsTotal($im) - 1 ;
$step['r'] = ($shadow['r'] - $background['r']) / $colorSteps ;
$step['g'] = ($shadow['g'] - $background['g']) / $colorSteps ;
$step['b'] = ($shadow['b'] - $background['b']) / $colorSteps ;
// for each index in the palette starting with white,
// set color to new calculated value
for ($n=$white;$n<$black;++$n)
imageColorSet($im,$n,
round(($n * $step['r']) + $background['r']),
round(($n * $step['g']) + $background['g']),
round(($n * $step['b']) + $background['b'])
) ;
// then set black to the new foreground color
imageColorSet($im,$black,$foreground['r'],$foreground['g'],$foreground['b']);
header("Content-type: image/png");
imagePNG($im);
imageDestroy($im);
/**
* @param $hex string 6-digit hexadecimal color
* @return array 3 elements 'r', 'g', & 'b' = int color values
* @desc Converts a 6 digit hexadecimal number into an array of
* 3 integer values ('r' => red value, 'g' => green, 'b' => blue)
*/
function hex2int($hex) {
return array(
'r' => hexdec(substr($hex, 0, 2)), // 1st pair of digits
'g' => hexdec(substr($hex, 2, 2)), // 2nd pair
'b' => hexdec(substr($hex, 4, 2)) // 3rd pair
);
}
/**
* @param $input string 6-digit hexadecimal string to be validated
* @param $default string default color to be returned if $input isn't valid
* @return string the validated 6-digit hexadecimal color
* @desc returns $input if it is a valid hexadecimal color,
* otherwise returns $default (which defaults to black)
*/
function validHexColor($input = '000000', $default = '000000') {
// A valid Hexadecimal color is exactly 6 characters long
// and eigher a digit or letter from a to f
return (eregi('^[0-9a-f]{6}$', $input)) ? $input : $default ;
}
/**
* @param $color array 3 elements 'r', 'g', & 'b' = int color values
* @param $tint float fraction of color $color to return
* @return array new color tinted to $tint of $color
* @desc returns a new color that is a tint of the original
* e.g. (255,127,0) w/ a tint of 0.5 will return (127,63,0)
*/
function tintOf($color,$tint) {
return array ( 'r' => round(((255-$color['r']) * (1-$tint)) + $color['r']),
'g' => round(((255-$color['g']) * (1-$tint)) + $color['g']),
'b' => round(((255-$color['b']) * (1-$tint)) + $color['b']) );
}
?>
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