PHP: Thumbnail erstellen

[sebbl]

Hallo,

in einer Bildergalerie oder ähnlichem ist es oft notwendig, eine Vorschau für die vorhandenen Bilder zu erstellen, um geringe Ladezeiten garantieren zu können.
Ich habe einen kleinen Code-Schnipsel, der diese Vorschaubilder erstellen soll.

Meine Bitte ist, dass Ihr ihn Euch mal zu Gemüte führt und mir ein kleines Feedback gebt, was noch angepasst und erweitert werden könnte / sollte.

Danke

Grüße

Der Schnipsel

<?php
	/*
		What does this to any image?
		This file creates a thumbnail of any via GET['src'] specified JPEG-Image
		Width and height of the new thumbnail has to be specified via GET['width'] and GET['height']
		You can also specify a background color via GET['bgcolor']
	*/
	$dflt_width = 100; // default width, only needed if GET['width'] is not specified
	$dflt_height = 100; // default height, only needed if GET['height'] is not specified
	$dflt_bgcolor = "#000000"; // default bgcolor, if GET['bgcolor'] is not specified
	
	/*
		transforms any specified hex-color into rgb and returns an array of r, g, b
		parameter:
			- color: hex-code
	*/
	function html2rgb($color)
	{
		if ($color[0] == '#')
			$color = substr($color, 1);
	
		if (strlen($color) == 6)
			list($r, $g, $b) = array($color[0].$color[1],
									 $color[2].$color[3],
									 $color[4].$color[5]);
		elseif (strlen($color) == 3)
			list($r, $g, $b) = array($color[0].$color[0], $color[1].$color[1], $color[2].$color[2]);
		else
			return false;
	
		$r = hexdec($r); $g = hexdec($g); $b = hexdec($b);
	
		return array($r, $g, $b);
	}

	header("Content-Type: image/jpeg"); // send header
	
	$thmbnl_width = isset($_GET["width"]) ? $_GET["width"] : $dflt_width; // get thumbnail width
	$thmbnl_height = isset($_GET["height"]) ? $_GET["height"] : $dftl_height; // get thumbnail height
	$thmbnl_bgcolor = isset($_GET["bgcolor"]) ? html2rgb($_GET["bgcolor"]) : $dflt_bgcolor; // get thumbnail background-color
	
	$src_filename = isset($_GET["src"]) ? $_GET["src"] : null; // get filename of specified image
	$src_size = @getimagesize($src_filename); // get size of specified image
	$src_width = is_array($src_size) ? $src_size[0] : $dflt_width; // width
	$src_height = is_array($src_size) ? $src_size[1] : $dfl_height; // height
	$src = @imagecreatefromjpeg($src_filename); // load image
	
	$thumbnail = imagecreatetruecolor($thmbnl_width, $thmbnl_height); // create new true color image 
	$bgcolor = imagecolorallocate($thumbnail, $thmbnl_bgcolor[0], $thmbnl_bgcolor[1], $thmbnl_bgcolor[2]); // create image background-color
	
	imagefill($thumbnail, 0, 0, $bgcolor); // fill image with specified color
	
	$src_props = $src_width / $src_height; // get image proportions
	$thmbnl_props = $thmbnl_width / $thmbnl_height; // get thumbnail proportions
	
	if($src_width > $thmbnl_width or $src_height > $thmbnl_height) // image dimensions greater than thumbnail dimensions?
	{
		if($src_width >= $src_height and $thmbnl_props <= $src_props) // width >= height, thumbnail proportions <= image proportions?
		{
			$width = $thmbnl_width; // use thumbnail width
			$height = ($thmbnl_width / $src_width) * $src_height;	// calc height (percentage)
		}
		else
		{
			$height = $thmbnl_height; // use thumbnail height
			$width = ($thmbnl_height / $src_height) * $src_width;	// calc width (percentage)			
		}
	}
	else // use image dimensions
	{
		$width = $src_width;
		$height = $src_height;
	}
	
	imagecopyresized($thumbnail, $src, ($thmbnl_width - $width) / 2, ($thmbnl_height - $height) / 2, 0, 0, $width, $height, $src_width, $src_height); // resize image and copy to thumbnail
	imagejpeg($thumbnail); // ouput thumbnail
?>

 

[Gumbo]

Wenn du das Vorschaubild bei jeder Anfrage erzeugst, ist die effektive Ladezeit nicht unbedingt geringer. Es wäre also sinnvoll, die Vorschaubilder zu speichern, um schneller darauf zugreifen zu können.

 

[sebbl]

Das stimmt natürlich. Deswegen habe ich auch eine Klasse erstellt, welche das Ausgeben, das Speichern oder das Ausgeben & Speichern des Bildes ermöglicht. Könnte ungefähr so aussehen.

<?php
	class image_handler
	{
		public $src;
		public $thmbnl_dflt_width = 100;
		public $thmbnl_dflt_height = 100;
		public $thmbnl_dflt_bgcolor = "#000000";
		public $thmbnl_dflt_filename = "thumb.jpg";
		public $thmbnl_dflt_directory = "thumbs/";
	
		public function __construct($src = null)
		{
			if(!is_null($src)) $this->src = $src;
		}
		
		/*
			transforms any specified hex-color into rgb and returns an array of r, g, b
			parameter:
				- color: hex-code
		*/
		private function html2rgb($color)
		{
			if ($color[0] == '#')
				$color = substr($color, 1);
			
			if (strlen($color) == 6)
				list($r, $g, $b) = array($color[0].$color[1],
										 $color[2].$color[3],
										 $color[4].$color[5]);
			elseif (strlen($color) == 3)
				list($r, $g, $b) = array($color[0].$color[0], $color[1].$color[1], $color[2].$color[2]);
			else
				return false;
		
			$r = hexdec($r); $g = hexdec($g); $b = hexdec($b);
		
			return array($r, $g, $b);
		}
		
		public function create_thumbnail($mode = 0, $output_filename = null, $output_width = null, $ouput_height = null, $output_bgcolor = null, $output_directory = null)
		{			
			$dflt_width = $this->thmbnl_dflt_width; // default width
			$dflt_height = $this->thmbnl_dflt_height; // default height
			$dflt_bgcolor = $this->thmbnl_dflt_bgcolor; // default bgcolor
			$dflt_filename = $this->thmbnl_dflt_filename; // default filename
			$dflt_directory = $this->thmbnl_dflt_directory; // default directory
			
			$thmbnl_width = !is_null($output_width) ? $output_width : $dflt_width; // get thumbnail width
			$thmbnl_height = !is_null($output_height) ? $output_height : $dflt_height; // get thumbnail height
			$thmbnl_bgcolor = $this->html2rgb((!is_null($output_bgcolor) ? $output_bgcolor : $dflt_bgcolor)); // get thumbnail background-color
			$thmbnl_filename = !is_null($output_filename) ? $output_filename : $dflt_filename; // get thumbnail filename
			$thmbnl_directory = !is_null($output_directory) ? $output_directory : $dflt_directory; // get thumbnail directory
			
			$src_filename = $this->src; // get filename of specified image
			$src_size = @getimagesize($src_filename); // get size of specified image
			$src_width = is_array($src_size) ? $src_size[0] : $dflt_width; // width
			$src_height = is_array($src_size) ? $src_size[1] : $dfl_height; // height
			$src = @imagecreatefromjpeg($src_filename); // load image
			
			$thumbnail = imagecreatetruecolor($thmbnl_width, $thmbnl_height); // create new true color image 
			$bgcolor = imagecolorallocate($thumbnail, $thmbnl_bgcolor[0], $thmbnl_bgcolor[1], $thmbnl_bgcolor[2]); // create image background-color
			
			imagefill($thumbnail, 0, 0, $bgcolor); // fill image with specified color
			
			$src_props = $src_width / $src_height; // get image proportions
			$thmbnl_props = $thmbnl_width / $thmbnl_height; // get thumbnail proportions
			
			if($src_width > $thmbnl_width or $src_height > $thmbnl_height) // image dimensions greater than thumbnail dimensions?
			{
				if($src_width >= $src_height and $thmbnl_props <= $src_props) // width >= height, thumbnail proportions <= image proportions?
				{
					$width = $thmbnl_width; // use thumbnail width
					$height = ($thmbnl_width / $src_width) * $src_height;	// calc height (percentage)
				}
				else
				{
					$height = $thmbnl_height; // use thumbnail height
					$width = ($thmbnl_height / $src_height) * $src_width;	// calc width (percentage)			
				}
			}
			else // use image dimensions
			{
				$width = $src_width;
				$height = $src_height;
			}
			
			imagecopyresized($thumbnail, $src, ($thmbnl_width - $width) / 2, ($thmbnl_height - $height) / 2, 0, 0, $width, $height, $src_width, $src_height); // resize image and copy to thumbnail
			
			
			if($mode == 0) // save thumbnail width specified output filename
			{
				imagejpeg($thumbnail, $thmbnl_directory . $thmbnl_filename);
			}
			elseif($mode == 1) // display thumbnail
			{
				header("Content-Type: image/jpeg"); // send header
				imagejpeg($thumbnail); // ouput thumbnail
			}
			else // save & display thumbnail
			{
			
			}
		}
	}
?>

Aufruf wie folgt:

	include("class_image_handler.php");
	
	$image_handler = new image_handler($_GET["src"]);
	$image_handler->thmbnl_dflt_width = 100;
	$image_handler->thmbnl_dflt_height = 100;
	$image_handler->thmbnl_dflt_bgcolor = "#000000";
	$image_handler->thmbnl_dflt_filename = "thumb.jpg";
	$image_handler->thmbnl_dflt_directory = "";
	$image_handler->create_thumbnail(1);

Was man auf jeden Fall noch ergänzen könnte wäre PNG-Unterstützung. Außerdem werden momentan mögliche Fehlermeldungen zum Großteil einfach unterdrückt.