How do I programmatically check whether a GIF image is animated?

Question

Here is a link to another question I asked concerning the same project I am working on. I think that bit of background will be helpful.

For those that are too lazy to open a new tab to that question, I'll summarize what I'm trying to do here: I've downloaded about 250,000 images from 4scrape and I want to go through the GIFs and find which ones are animated or not. I need to do this programmatically, because I really don't feel my soul (or my relationship with my girlfriend) could use looking at a couple thousand GIFs from 4chan to see if they are animated or not. If you know the nature of 4chan, then you know the nature of the images (i.e. "tits or GTFO").

I know PHP and Python, but would be willing to explore other solutions. A stand-alone piece of software that works on Windows would also work.

Thanks a lot!

Answer 1

With Python and PIL:

from PIL import Image
gif = Image.open('path.gif')
try:
    gif.seek(1)
except EOFError:
    isanimated = False
else:
    isanimated = True

Answer 2

If you're on Linux (or any system with ImageMagick) you can use a one-liner shell script and identify program:

identify *.gif | fgrep '.gif[1] '

I know you said you prefer PHP and Python, but you also said you are willing to explore other solutions. :)

Answer 3

Pillow 2.9.0 added is_animated:

This adds the property is_animated, to check if an image has multiple layers or frames.

Example usage:

from PIL import Image
print(Image.open("test.gif").is_animated)

Answer 4

I've never seen a program that will tell you this. But GIF is a block structured format and you can check if the block indicating animated GIF is present in your files.

From wikipedia article noted below: at offset 0x30D an Application Extension (ie: 3 byte magic number 21 FF 0B) block in the GIF file, followed by magic number 4E 45 54 53 43 41 50 45 32 9at offset 0x310 indicates that the rest of the file contains multiple images, and they should be animated.

Really the Wikipedia article explains it better and the format docs noted below expand on the Wiki article.

So you can parse the GIFs using a program written in Python (I parsed GIFs using C many years ago, it was mainly an exercise in moving the file pointer around and reading bytes). Determine if the AE is present with the correct 3 byte ID, and followed by the 9 byte magic number.

See http://en.wikipedia.org/wiki/Graphics_Interchange_Format#Animated_.gif

Also see http://www.martinreddy.net/gfx/2d/GIF87a.txt

Also see http://www.martinreddy.net/gfx/2d/GIF89a.txt

Sorry, best I can do for you.

Answer 5

A few solutions are given on the PHP docs page for the imagecreatefromgif function.

From the solutions I've read, this one seems the best due to its tighter memory requirements.

<?php
function is_ani($filename) {
    if(!($fh = @fopen($filename, 'rb')))
        return false;
    $count = 0;
    //an animated gif contains multiple "frames", with each frame having a
    //header made up of:
    // * a static 4-byte sequence (\x00\x21\xF9\x04)
    // * 4 variable bytes
    // * a static 2-byte sequence (\x00\x2C)

    // We read through the file til we reach the end of the file, or we've found
    // at least 2 frame headers
    while(!feof($fh) && $count < 2) {
        $chunk = fread($fh, 1024 * 100); //read 100kb at a time
        $count += preg_match_all('#\x00\x21\xF9\x04.{4}\x00\x2C#s', $chunk, $matches);
    }
    fclose($fh);
    return $count > 1;
}
?>

Answer 6

Read the GIF89A specification and extract the information. http://www.w3.org/Graphics/GIF/spec-gif89a.txt

Or easy and lazy and ready for a hack use the intergif program which can extract the single images out of an animated gif. Extract into a temp directory and look how many files you get. http://utter.chaos.org.uk/~pdh/software/intergif/download.htm