<?PHP
error_reporting(E_ALL ^ E_NOTICE);
/*
rgb.php
An interactive example of the additive nature of the RGB color model
*/
if (isset($_REQUEST['hex'])) {
// if a hex value is passed, use it
$imColor = hex2int(validHexColor($_REQUEST['hex'])) ;
} else {
// otherwise use red, green, & blue values
$imColor['r'] = validIntColor($_REQUEST['red']);
$imColor['g'] = validIntColor($_REQUEST['green']);
$imColor['b'] = validIntColor($_REQUEST['blue']);
}
$im = imageCreateFromPNG('rgb.png') ;
// determine the indicies of white and the three primaries
$rIndex = imageColorExact ($im, 0xFF, 0x00, 0x00); // get index of red
$gIndex = imageColorExact ($im, 0x00, 0xFF, 0x00); // get index of green
$bIndex = imageColorExact ($im, 0x00, 0x00, 0xFF); // get index of blue
$wIndex = imageColorExact ($im, 0xFF, 0xFF, 0xFF); // get index of white
// redefine the colors to the input value
// first set pure red, green, and blue portions to their respective components of $imColor
imageColorSet($im, $rIndex, $imColor['r'], 0, 0);
imageColorSet($im, $gIndex, 0, $imColor['g'], 0);
imageColorSet($im, $bIndex, 0, 0, $imColor['b']);
// then set the combined portion to all components of $imColor
imageColorSet($im, $wIndex, $imColor['r'], $imColor['g'], $imColor['b']);
header('Content-type: image/png');
imagePNG($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 $input int integer to be validated
* @param $default int default value returned if $input isn't valid
* @return int the validated integer
* @desc returns $input if it is a valid integer color,
* otherwise returns $default (which defaults to 0)
*/
function validIntColor($input, $default = 0) {
// A valid integer color is between 0 and 255
return (is_numeric($input)) ? (int) max(min($input, 255),0) : (int) $default ;
}
?>
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