How to extract frames of an animated GIF with PHP

Question

I search for a long time how to extract frames from an animated GIF with PHP... unfortunaly I just found how to get their duration...

I really need to extract the GIF frames and their duration to apply some resize, rotate, etc, on each and then to regenerate the GIF with edited frames !

I don't want to use any software, external library (like ImageMagick), just PHP: in fact I need to allow my class http://phpimageworkshop.com/ to work with animated GIF.

If you have any idea, I'm listening you ^^ !

As you can see I find a class that resize each frame only with PHP: gist.github.com/3769812 So this is possible but the class is not well documented. I will check and understand all of these lines if nobody has a more simple solution :s — Sybio
– Sybio, Commented Sep 23, 2012 at 11:34

Joncom · Accepted Answer · 2013-07-08 00:09:36Z

I spent my day creating a class based on this one to achieve what I wanted using only PHP!

You can find it here: https://github.com/Sybio/GifFrameExtractor

Thanks for your answers!

Chris Henry · Accepted Answer · 2012-09-23 14:34:04Z

Well, I don't really recommend doing it this way, but here's an option. Animated gifs are actually just a number of gifs concatenated together by a separator, "\x00\x21\xF9\x04". Knowing that, you simply pull the image into PHP as a string, run an explode, and loop through the array running your transformation. The code could look something like this.

$image_string = file_get_contents($image_path); $images = explode("\x00\x21\xF9\x04", $image_string); foreach( $images as $image ) { // apply transformation } $new_gif = implode("\x00\x21\xF9\x04", $images);

I'm not 100% sure of the specifics of re-concatenating, the image, but here's the wikipedia page regarding the file format of animated GIFs.

I tried your solution but it doesn't work :( Thanks anyway ^^
It seems it's a bit more complicated than this for what the OP was asking (there are headers and other stuff to consider). But I came here looking for a way to count how many frames there were in a GIF file, and that binary separator was a lifesaver! I just did substr_count($image_string, "\x00\x21\xF9\x04"), and that's faster and less memory intensive than reading the entire image into memory with something like Imagick. Thank you!

stil · Accepted Answer · 2016-10-22 21:10:43Z

I am the author of https://github.com/stil/gif-endec library, which is significantly faster (about 2.5 times) at decoding GIFs than Sybio/GifFrameExtractor library from accepted answer. It has also less memory usage, because it allows you to process one frame after another at decode time, without loading everything to memory at once.

Small code example:

<?php require __DIR__ . '/../vendor/autoload.php'; use GIFEndec\Events\FrameDecodedEvent; use GIFEndec\IO\FileStream; use GIFEndec\Decoder; /** * Open GIF as FileStream */ $gifStream = new FileStream("path/to/animation.gif"); /** * Create Decoder instance from MemoryStream */ $gifDecoder = new Decoder($gifStream); /** * Run decoder. Pass callback function to process decoded Frames when they're ready. */ $gifDecoder->decode(function (FrameDecodedEvent $event) { /** * Write frame images to directory */ $event->decodedFrame->getStream()->copyContentsToFile( __DIR__ . "/frames/frame{$event->frameIndex}.gif" ); });

Flavius · Accepted Answer · 2012-09-23 14:00:15Z

1

I don't want to use any software, external library (like ImageMagick)

Well, good luck with that, because 90% of the functionality the Zend Engine exports to the PHP runtime comes from libraries.

If you have any idea, I'm listening you ^^ !

Parse the binary data in the GIF format. You could use unpack(), among other things.

edited Sep 23, 2012 at 14:00

answered Sep 23, 2012 at 13:39

Flavius

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3 Comments

Chris Henry Over a year ago

How would you use unpack to break out the frames of an animated gif?

Flavius Over a year ago

My answer mentions "among other things" like regular programming constructs, loops, conditions. Not "unpack()" is the keyword there, but parse.

Chris Henry Over a year ago

Agreed that parsing is the key here. It just doesn't look like unpack() is a viable way to get animated gif frames, at least from what I can tell by looking through formats it supports. php.net/manual/en/function.pack.php

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