Dynamically resample hotlinked images using php

Question

I have an images directory, some with massive resolutions, so I'd like to serve a much lower resolution version if they get hotlinked and I'm also overlaying a repeating image (like a watermark) informing the viewer that the image is stolen and where they can find the genuine original.

I've got the resampling working fine but when I add the function for the no hotlink image overlay, it doesn't work. The thing is, I know the watermarking script works too, on it's own, because I've used it elsewhere in another file on the site. Unfortunately I can't tell what the error is as the hotlink test sites don't output errors, they just show an empty image placeholder, and my host's log files are all like greek to me.

This is the script I have at the moment:

<?php
ini_set('memory_limit','250M');
$path = $_SERVER['DOCUMENT_ROOT'].$_SERVER['REQUEST_URI'];

class SimpleImage {

    var $image;
    var $image_type;

    function load($filename) {
        $image_info = getimagesize($filename);
        $this->image_type = $image_info[2];
        if( $this->image_type == IMAGETYPE_JPEG ) {
            $this->image = imagecreatefromjpeg($filename);
        } elseif( $this->image_type == IMAGETYPE_GIF ) {
            $this->image = imagecreatefromgif($filename);
        } elseif( $this->image_type == IMAGETYPE_PNG ) {
            $this->image = imagecreatefrompng($filename);
        }
    }
    function save($filename, $image_type=IMAGETYPE_JPEG, $compression=60, $permissions=null) {
        if( $image_type == IMAGETYPE_JPEG ) {
            imagejpeg($this->image,$filename,$compression);
        } elseif( $image_type == IMAGETYPE_GIF ) {
            imagegif($this->image,$filename);
        } elseif( $image_type == IMAGETYPE_PNG ) {
            imagepng($this->image,$filename);
        }
        if( $permissions != null) {
            chmod($filename,$permissions);
        }
    }
    function output($image_type=IMAGETYPE_JPEG) {
        if( $image_type == IMAGETYPE_JPEG ) {
            imagejpeg($this->image);
        } elseif( $image_type == IMAGETYPE_GIF ) {
            imagegif($this->image);
        } elseif( $image_type == IMAGETYPE_PNG ) {
            imagepng($this->image);
        }
        imagedestroy($image);
        exit();
    }
    function getWidth() {
        return imagesx($this->image);
    }
    function getHeight() {
        return imagesy($this->image);
    }
    function resizeToHeight($height) {
        $ratio = $height / $this->getHeight();
        $width = $this->getWidth() * $ratio;
        $this->resize($width,$height);
    }
    function resizeToWidth($width) {
        $ratio = $width / $this->getWidth();
        $height = $this->getheight() * $ratio;
        $this->resize($width,$height);
    }
    function scale($scale) {
        $width = $this->getWidth() * $scale/100;
        $height = $this->getheight() * $scale/100;
        $this->resize($width,$height);
    }
    function resize($width,$height) {
        $new_image = imagecreatetruecolor($width, $height);
        imagecopyresampled($new_image, $this->image, 0, 0, 0, 0, $width, $height, $this->getWidth(), $this->getHeight());
        $this->image = $new_image;
    }
    function nothot() {
        $hotlink = imagecreatefrompng('hotlink.png');
        $hw = imagesx($hotlink);
        $hh = imagesy($hotlink);
        $img_paste_x = 0;
        $img_paste_x = 0;
        while($img_paste_x < $this->getWidth()){
            $img_paste_y = 0;
            while($img_paste_y < $this->getHeight()){
                imagecopy($image, $hotlink, $img_paste_x, $img_paste_y, 0, 0, $hw, $hh);
                $img_paste_y += $hh;
            }
            $img_paste_x += $hw;
        }
        imagedestroy($hotlink);
    }

}
header('Content-Type: image/jpeg');
$image = new SimpleImage();
$image->load($path);
$image->resizeToWidth(600);
$image->nothot();
$image->output();
?>

Thanks for your help.

I am sure someone will comment if I am totally incorrect, but this will put a bigger load on your server than just serving the image itself. Perhaps it would be better to store a smaller version watermarked and serve that up instead of reprocessing the same subset of huge images repeatedly every time they are requested. Or even store them the first time, then skip the re-imaging. — horatio, Sep 13 '11 at 18:03
I agree this would be a lot easier and put less strain on the server, however I aim to use this script on a multi-user site, so if I had manually recreate a 'hotlink' version for each of my users' uploads I wouldn't have time for anything else, so I need an automatic way to do this for me. — Ben, Sep 13 '11 at 18:40

score 1 · Accepted Answer · answered Sep 13 '11 at 17:57

1

Change:

 imagecopy($image, $hotlink, $img_paste_x, $img_paste_y, 0, 0, $hw, $hh);

to:

 imagecopy($this->image, $hotlink, $img_paste_x, $img_paste_y, 0, 0, $hw, $hh);

Also not sure about the way you get the $path, some checks on whether the image exists wouldn't go a miss.

answered Sep 13 '11 at 17:57

Lawrence Cherone

46,049
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I thought it might be something simple like that. I will look into the path validation thing, but it won't create a problem for me if the image doesn't exist, only for the hotlinker. Thanks! – Ben Sep 13 '11 at 18:47

Dynamically resample hotlinked images using php

1 Answers1