Round Gradients

[lupus2k5]

I have a script that makes top-to-bottom gradients, but I was wondering if anybody knew how to make a circular gradient, one that starts in the center, then fades to the other color in a circular way (first color=circle in the middle, then fades to second color).
Here's the code for the straight gradient maker:

<?php
class gradient_image {
    var $from;
    var $to;
    var $steps;
    var $width;
    var $height;

/**
 * gradient_image::gradient_image() - Contrutor da classe
 *
 * @param $from Cor inicial em notação hexadecimal
 * @param $to Cor final em notação hexadecimal
 * @param $steps Número de etapas do gradiente
 * @param $width Largura da imagem
 * @param $height Altura da imagem
 **/
function gradient_image($from, $to, $steps, $width, $height)
{
    $this->from   = $this->getHexValues($from);
    $this->to     = $this->getHexValues($to);
    $this->steps  = $steps;
    $this->width  = $width;
    $this->height = $height;
}

/**
 * gradient_image::getHexValues() - Cria um array com valores RGB a partir de uma cor em formato hexadecimal
 *
 * @param $color Cor em formato hexadecimal a ser convertida
 * @return array Array com os valores RGB em formato decimal
 * @access private
 **/
function getHexValues($color)
{
    $color = substr($color, -6);
    return array(hexdec(substr($color, 0, 2)), hexdec(substr($color, 2, 2)), hexdec(substr($color, 4, 2)));
}

/**
 * gradient_image::createArray() - Cria um array com as cores do gradiente
 *
 * @return array Array com as cores do gradiente
 **/
function createArray()
{
    $red   = ($this->to[0] - $this->from[0]) / ($this->steps-1);
    $green = ($this->to[1] - $this->from[1]) / ($this->steps-1);
    $blue  = ($this->to[2] - $this->from[2]) / ($this->steps-1);

    for($i = 0; $i < $this->steps; $i++) {
        $newred   = $this->from[0] + round($i * $red);
        $newgreen = $this->from[1] + round($i * $green);
        $newblue  = $this->from[2] + round($i * $blue);
        $return[$i] = array($newred, $newgreen, $newblue);
    }

    return $return;
}

/**
 * gradient_image::createImage() - Cria uma imagem
 *
 * @param boolean $vertical Define se o gradiente será criado no sentido vertical
 * @return resource Recurso da imagem criada
 **/
function createImage($vertical = true)
{
    if ($vertical) {
      if ($this->steps > $this->width)  $this->steps = $this->width;
    } else {
      if ($this->steps > $this->height) $this->steps = $this->height;
    }

    $im = imagecreatetruecolor($this->width, $this->height);
    $gradient = $this->createArray();

    foreach ($gradient as $color) {
        $red   = $color[0];
        $green = $color[1];
        $blue  = $color[2];
        $colors[] = imagecolorallocate($im, $red, $green, $blue);
    }

    if ($vertical) {
        $step = $this->width / $this->steps;
        $y = $this->height;
        if ($step == 1)
            for ($x = 0, $i = 0; $x < $this->width; $x += $step, $i++)
              imageline($im, $x, 0, $x, $y, $colors[$i]);
        else
            for ($x = 0, $i = 0; $x < $this->width; $x += $step, $i++)
              imagefilledrectangle($im, $x, 0, $x + $step, $y, $colors[$i]);
    } else {
        $step = $this->height / $this->steps;
        $x = $this->width;
        if ($step == 1)
            for ($y = 0, $i = 0; $y < $this->height; $y += $step, $i++)
                imageline($im, 0, $y, $x, $y, $colors[$i]);
        else
            for ($y = 0, $i = 0; $y < $this->height; $y += $step, $i++)
                imagefilledrectangle($im, 0, $y, $x, $y + $step, $colors[$i]);
    }

    return $im;
}

/**
 * gradient_image::createPNG() - Cria uma imagem em formato PNG a partir do recurso de imagem especificado
 *
 * @param boolean $im Recurso de imagem a ser utilizado
 * @param boolean $interlaced Define se a imagem será entrelaçada
 * @return null
 **/
function createPNG($im = false, $interlaced = false)
{
    if (!$im) $im = $this->createImage();
    if ($interlaced) imageinterlace ($im, 1);
    header("Content-type: " . image_type_to_mime_type(IMAGETYPE_PNG));
    imagepng($im);
    imagedestroy($im);
}

/**
 * gradient_image::createJPEG() - Cria uma imagem em formato JPEG a partir do recurso de imagem especificado
 *
 * @param resource $im Recurso de imagem a ser utilizado
 * @param boolean $progressive Define se a imagem será progressiva
 * @param integer $quality Define a qualidade da imagem
 * @return null
 **/
function createJPEG($im = false, $progressive = false, $quality = 75)
{
    if (!$im) $im = $this->createImage();
    if ($progressive) imageinterlace ($im, 1);
    header("Content-type: " . image_type_to_mime_type(IMAGETYPE_JPEG));
    imagejpeg($im, '', $quality);
    imagedestroy($im);
}
}

?>

Sorry, the comments are not in English.

[madwormer2]

Messing around with your functions (sorry, I took them out of the class) I made something, but it's not very good, but some of the results are quite cool.

<?php
function getHexValues($color)
{
	$color = substr($color, -6);
	return array(hexdec(substr($color, 0, 2)), hexdec(substr($color, 2, 2)), hexdec(substr($color, 4, 2)));
}
function createArray($to,$from,$steps)
{
	$red   = ($to[0] - $from[0]) / ($steps-1);
	$green = ($to[1] - $from[1]) / ($steps-1);
	$blue  = ($to[2] - $from[2]) / ($steps-1);

for($i = 0; $i < $steps; $i++) {
	$newred   = $from[0] + round($i * $red);
	$newgreen = $from[1] + round($i * $green);
	$newblue  = $from[2] + round($i * $blue);
	$return[$i] = array($newred, $newgreen, $newblue);
}

return $return;
}
$width = 500;
$height = 500;
$steps = 200;
$step = $width/$steps;
$middle = $width / 2;
// Create transparent image
	$im = imagecreatetruecolor($width, $height);
	imageSaveAlpha($im, true);
	imagealphablending($im,false);
	$color = imagecolorallocatealpha($im,0,0,0,127);
	imagefilledrectangle($im,0,0,$width,$height,$color);
	imagealphablending($im,true);
// Allocate array and loop
$start = getHexValues('8866FF');
$stop = getHexValues('CCFF00');
$ar = createArray($start,$stop,$steps+1);
$ar = array_reverse($ar,true);
foreach($ar as $k=> $v){
$k = $k+1;
	$color = imagecolorallocate($im,$v[0],$v[1],$v[2]);
	imagefilledellipse ( $im, $middle, $middle, $k*$step, $k*$step, $color );
}
header("Content-type: " . image_type_to_mime_type(IMAGETYPE_PNG));
imagepng($im);
imagedestroy($im);

?>