index.php

<?php
	/**
	 * View image dynamically
	 * 
	 * @return mixed
	 */
	function view_image(){
		ini_set('gd.jpeg_ignore_warning', true);
		$path = $_GET["path"];
		
		if(@getimagesize($path) === FALSE){
			$path = getcwd().'/assets/images/default.jpg';
		}

	 //getting extension type (jpg, png, etc)
	    $type = explode(".", $path);
	    $ext = strtolower($type[sizeof($type)-1]);

	    $ext = (!in_array($ext, array("jpeg","png","gif"))) ? "jpeg" : $ext;

	    //get image size
	    $size = getimagesize($path);

	    $width = $size[0];
	    $height = $size[1];
	    
	    //get source image
	    $func = "imagecreatefrom".$ext;
	    $source = $func($path);
	    
	    //setting default values
	    
	    $new_width = $width;
	    $new_height = $height;
	    $k_w = 1;
	    $k_h = 1;
	    $dst_x =0;
	    $dst_y =0;
	    $src_x =0;
	    $src_y =0;
	    
	    //selecting width and height

	    if($_GET["width"]==null && $_GET["height"]==null)
	    {
	        $new_height = $height;
	        $new_width = $width;
	    }
	    else if($_GET["width"]==null)
	    {
	        $new_height = $_GET["height"];
	        $new_width = ($_GET["height"])/$height;
	    }
	    else if($_GET["height"]==null)
	    {
	        $new_height = ($height*$_GET["width"])/$width;
	        $new_width = $_GET["width"];
	    }
	    else
	    {
	        $new_width = $_GET["width"];
	        $new_height = $_GET["height"];
	    }
	    
	    //secelcting_offsets
	        
	        if($new_width>$width )//by width
	        {
	            $dst_x = ($new_width-$width)/2;
	        }
	        if($new_height>$height)//by height
	        {
	            $dst_y = ($new_height-$height)/2;
	        }
	        if( $new_width<$width || $new_height<$height )
	        {
	            $k_w = $new_width/$width;
	            $k_h = $new_height/$height;
	            
	            if($new_height>$height)
	            {
	                $src_x  = ($width-$new_width)/2;
	            }
	            else if ($new_width>$width)
	            {
	                    $src_y  = ($height-$new_height)/2;
	            }
	            else
	            {
	                if($k_h>$k_w)
	                {
	                    $src_x = round(($width-($new_width/$k_h))/2);
	                }
	                else
	                {
	                    $src_y = round(($height-($new_height/$k_w))/2);
	                }
	            }
	        }
	    $output = imagecreatetruecolor( $new_width, $new_height);
	    
	    //to preserve PNG transparency
	    if($ext == "png")
	    {
	        //saving all full alpha channel information
	        imagesavealpha($output, true);
	        //setting completely transparent color
	        $transparent = imagecolorallocatealpha($output, 0, 0, 0, 127);
	        //filling created image with transparent color
	        imagefill($output, 0, 0, $transparent);
	    }

	    imagecopyresampled( $output, $source,  $dst_x, $dst_y, $src_x, $src_y, 
	                        $new_width-2*$dst_x, $new_height-2*$dst_y, 
	                        $width-2*$src_x, $height-2*$src_y);
	    //free resources
	    ImageDestroy($source);

	    //output image
	    header('Content-Disposition: inline');
	    header('Content-Type: image/'.$ext);
	    $func = "image".$ext;
	    $func($output); 
	    
	    //free resources
	    ImageDestroy($output);
		exit();
	}

	
	view_image();