CODEWITHSUNDEEP
phpanimated-gif
CodeDevelopr
CodeDevelopr

Reputation: 1265

Do animated Gif files have GIFGIF embedded in them?

I am currently re-writing an existing tool in PHP that another person started for optimizing images, for gif images,I will convert to png and then optimize the png file. For animated gifs I will run through the program called Gifsicle which can optimize animated gif images.

In some of the existing codebase, the other guy identified animated gif images with the file extension gifgif as you can see in the snippets below, they contain all the code that references this gifgif.

I have search Google and I cannot find a mention of a gifgif file anywhere, in addition I have never in my life heard of one.

Can someone help me figure out does the actual extension gifgif exist? Is it possibly something that is embedded in animated gif files?

The code...

$types = array("gif", "png", "gifgif", "jpg", "jpeg", "bmp");

and

if (substr($type, 0, 6) === "gifgif") 
{
    $type = "gifgif";
}

and 

case "gifgif":
    $dest_file .= ".gif";
    $cmd = "/usr/bin/gifsicle -O2 $src_file > $dest_file";
    exec($cmd, $return, $error);

Upvotes: 2

Views: 255

Answers (2)

Aleks G
Aleks G

Reputation: 57316

gifgif is not a valid extension - and by all means is not a valid way to check whether the file is an animated gif file. In order to check whether the file is an animated gif, you need to actually parse the content of the file and check for frame headers. This function will do it simply:

<?php
function is_ani($filename) {
    return (bool)preg_match('#(\x00\x21\xF9\x04.{4}\x00\x2C.*){2,}#s', file_get_contents($filename));
}
?>

P.S. This is not my function, but borrowed from http://php.net/manual/en/function.imagecreatefromgif.php There is another version given in the same post. That version of the function reads the file in chunks and checks each individual chunk, however this approach will not correctly, because the header may end up being split between two chunks.

Upvotes: 1

Quentin
Quentin

Reputation: 943213

This is not a standard extension and the code you show appears to care only about file extensions.

Presumably the developer of the system you are using came up with the convention and it is unique to that system.

Upvotes: 2

Related Questions