create thumbnails from uploaded images PHP

[MisterWhite]

i have a simple html/php file setup.

Spoiler

<form action="<?php echo htmlspecialchars($_SERVER['PHP_SELF']); ?>" method="post" enctype="multipart/form-data">
Ikelk pora <input type="file" name="for_thumb"><br>
<input type="submit" name="submit" value="Kelt">

 

PHP part

Spoiler

$fullpath= "thumb/".$_FILES['for_thumb']['name'];
		@$mime=getimagesize($_FILES['for_thumb']['tmp_name']);
		if($mime['mime']=="image/jpeg")
		{	
			$dst_img= imagecreatetruecolor(150,84);
			$Size=getimagesize($_FILES['for_thumb']['tmp_name']);
			$src_img= imagecreatefromjpeg($_FILES['for_thumb']['tmp_name']);
			imagecopyresampled($dst_img,$src_img,0,0,0,0,150,84,$Size[0],$Size[1]);
			imagejpeg($dst_img, $fullpath, 100);
			}
		else
			echo" Not JPG";
        }
        foreach(glob("thumb/*") as $file)// this part needs fixing
            echo "<img src='$file'>  ";

 

So long story short uploaded image gets resized and then all images in the folder thumb are printed. Though the printing part is good for testing but isn't efficient in real world applications. How should i replace my sluggish code?

[mariushm]

You shouldn't use any information that user could have submitted without escaping or making safe.

In your case, it's not smart  to use put $_FILES['for_thumb']['name'] in the $fullpath variable, because an "evil" user may send a specially crafted server request to change the name to some binary data or whatever they want. Also, users may use the same name for several files so you may overwrite older images or thumbs this way.

My first choice would be to generate a MD5 or a SHA256 of the contents of the image and then save the hash in the database or whatever you use, then save the thumbnail with a path something like this  /thumbs/a/a4/a4633f4e.....jpg  where the "a" and "a4" folders are simply formed from the first two characters in the hash.

This is optional, but the reasoning for this is because some file systems don't "like", they're slower when there's more than a few thousand files stored into a single folder. By making a folder structure like that, there's gonna be a few images in each folder branch, instead of thousands of thumbs in just one folder.

 

As for the foreach, I don't see the need for it.. aren't you creating the thumbnails a few lines of code above? Why not put those paths in an array as the pictures are created and read the array back at that later point? This way there's no need to parse the folder where the thumbs are created.

 

Also, you should be careful about imagecreatefromjpeg , because it's kind of memory hungry. Don't know how your code is going to use so i'm throwing this situation out there: some people may upload pictures made with their phone cameras, you may have 8-16 megapixel pictures (like, 5000 x 4000) and these pictures when they're decoded to raw images they may use up to 15-30 MB of memory. Some php installations don't allow so much memory usage per script and may crash or the image may fail to load - you may want to at least use the @  character in front of the functions to prevent errors and warnings from being dumped on the output and to test the return of those functions.

 

On a image sharing site I wrote in an afternoon (something super basic), I just resorted to installing imagemagick on the server and calling that to convert images instead of using the built in functions.

[burnttoastnice]

3 hours ago, mariushm said:

I just resorted to installing imagemagick on the server

I use the same utility for my application - it's excellent.

[MisterWhite]

13 hours ago, mariushm said:

As for the foreach, I don't see the need for it.. aren't you creating the thumbnails a few lines of code above? Why not put those paths in an array as the pictures are created and read the array back at that later point? This way there's no need to parse the folder where the thumbs are created.

My idea:

Select image, hit upload, see the first thumbnail. Select again (if you will), hit upload and now see two thumbnails and so on.

Since the page refreshes itself after pressing the upload button i cannot create an array of paths (at least to my knowledge) because it will keep resetting the array.

[HarryNyquist]

2 hours ago, MisterWhite said:

My idea:

Select image, hit upload, see the first thumbnail. Select again (if you will), hit upload and now see two thumbnails and so on.

Since the page refreshes itself after pressing the upload button i cannot create an array of paths (at least to my knowledge) because it will keep resetting the array.

This is where you use AJAX to change part of the page without reloading. jQuery has shorthand notations to make doing AJAX easier.