Gradient generator

gradient.php

<?php
// get some values for the params from get; we also have some default values that render an 100x100 image with a horizontal gradient from black to white
$width = 100;
if (isset($_GET['width'])) // the width of out output pic
{
	$width = filter_var($_GET['width'], FILTER_VALIDATE_INT); // I am not using filter_input without the isset() test because some applications will use url rewriting 
}
$height = 100;
if (isset($_GET['height'])) // height of the pic
{
	$height = filter_var($_GET['height'], FILTER_VALIDATE_INT);
}

$from_r = 0;
if (isset($_GET['from_r'])) // red component of the starting color
{
	$from_r = filter_var($_GET['from_r'], FILTER_VALIDATE_INT);
}
$from_g = 0;
if (isset($_GET['from_g'])) // start color: green
{
	$from_g = filter_var($_GET['from_g'], FILTER_VALIDATE_INT);
}
$from_b = 0;
if (isset($_GET['from_b'])) // start color: blue
{
	$from_b = filter_var($_GET['from_b'], FILTER_VALIDATE_INT);
}
$from_a = 0;
if (isset($_GET['from_a'])) // start alpha: plain
{
	$from_a = filter_var($_GET['from_a'], FILTER_VALIDATE_INT);
}


$to_r = 255;
if (isset($_GET['to_r'])) // red component of our final color 
{
	$to_r = filter_var($_GET['to_r'], FILTER_VALIDATE_INT);
}
$to_g = 255;
if (isset($_GET['to_g'])) // final: green
{
	$to_g = filter_var($_GET['to_g'], FILTER_VALIDATE_INT);
}
$to_b = 255;
if (isset($_GET['to_b'])) // final: blue
{
	$to_b = filter_var($_GET['to_b'], FILTER_VALIDATE_INT);
}
$to_a = 0;
if (isset($_GET['to_a'])) // final alpha: plain
{
	$to_a = filter_var($_GET['to_a'], FILTER_VALIDATE_INT);
}

// direction for each of the gradient lines; 
// using the default values the picture will be black at the top and white at the bottom; 
// with the same values but changing this one will render a picture white on the right side and black on its left side
$vertical = false;
if (isset($_GET['vertical'])) 
{
	$vertical = true;
}

gradient($width, $height, $from_r, $from_g, $from_b, $from_a, $to_r, $to_g, $to_b, $to_a, $vertical);


function gradient($image_width, $image_height,$c1_r, $c1_g, $c1_b, $c1_a, $c2_r, $c2_g, $c2_b, $c2_a, $vertical=false)
{
	// make sure that the parameters are what we need them to be
	$image_width 	= 	intval($image_width);
	$image_height 	= 	intval($image_height);
	$c1_r 			= 	intval($c1_r);
	$c1_g 			= 	intval($c1_g);
	$c1_b 			= 	intval($c1_b);
	$c1_a 			= 	intval($c1_a);
	$c2_r 			= 	intval($c2_r);
	$c2_g 			= 	intval($c2_g);
	$c2_b 			= 	intval($c2_b);
	$c2_a 			= 	intval($c2_a);
	$vertical 		= 	(bool)$vertical;

	// create an image; this will be our output
	$image  = imagecreatetruecolor($image_width, $image_height);

	// render gradient step by step
	for($i=0; $i<$image_height; $i++)
	{
		// get each color component for this step
		$color_r = floor($i * ($c2_r-$c1_r) / $image_height)+$c1_r;
		$color_g = floor($i * ($c2_g-$c1_g) / $image_height)+$c1_g;
		$color_b = floor($i * ($c2_b-$c1_b) / $image_height)+$c1_b;
		$color_a = floor($i * ($c2_a-$c1_a) / $image_height)+$c1_a;
		
		// create this color
		$color = imagecolorallocatealpha($image, $color_r, $color_g, $color_b, $color_a);

		// draw a line using this color
		imageline($image, 0, $i, $image_width, $i, $color);
	}

	if($vertical) // rotate the image 
	{
		// php.net/imagerotate: "Note: This function is only available if PHP is compiled with the bundled version of the GD library."
		// so if this function doesn't work you must find another way to rotate the image;
		// one option is to use the function that I found googling and I added to the end of this file called rotateImage
		$image = imagerotate($image, 90, 0); 
	} 
	
	// we will output the image now.. if you want you can save the picture insead using the second parameter for the imagepng function
	header('Content-type: image/png'); // set headers
	imagepng($image); // or imagejpeg, imagegif..
	imagedestroy($image); // free memory
	die;
}

function rotateImage($img, $rotation) 
{
  $width = imagesx($img);
  $height = imagesy($img);
  switch($rotation) 
  {
    case 90: 
		$newimg= @imagecreatetruecolor($height , $width );
		break;
    case 180: 
		$newimg= @imagecreatetruecolor($width , $height );
		break;
    case 270: 
		$newimg= @imagecreatetruecolor($height , $width );
		break;
    case 0: 
		return $img;
		break;
    case 360: 
		return $img;
		break;
  }
  if($newimg) 
  {
    for($i = 0;$i < $width ; $i++) 
    {
      for($j = 0;$j < $height ; $j++) 
      {
        $reference = imagecolorat($img,$i,$j);
        switch($rotation) 
        {
          case 90: if(!@imagesetpixel($newimg, ($height - 1) - $j, $i, $reference )){return false;}break;
          case 180: 
          	if(!@imagesetpixel($newimg, $width - $i-1, ($height - 1) - $j, $reference ))
          	{
          		return false;
          	}
          	break;
          case 270: if(!@imagesetpixel($newimg, $j, $width - $i, $reference )){return false;}break;
        }
      }
    } 
	return $newimg;
  }
  return false;
}