Issue 31 has been merged into this issue.

It would be so awesome if this library could resize animated gif's !

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There seems to be quite a bit of interest in resizing animated GIFs.

I can't make any promises, but I will see if it is feasible to retrofit 
Thumbnailator to support animated images.

Excellent project, I'm currently using it in my current project, but I have a 
need to support animated gifs, any pointer that anyone can give around?

Hello, I'm willing to sponsor a work on animated GIF feature. Please let me 
know if you are interested.

First of all, to get a full grasp of this issue, I'm going to present some 
background regarding Thumbnailator.

Thumbnailator is design in around a "pipeline" model to read and process a 
_single_ image, and create a thumbnail which is written to some destination.

The internals have been designed as simple as possible, but still maintains 
extensibility and code reuse by defining interfaces between each of the 
components (I/O, resizing, filtering, etc.), and the unit of work that the 
interface passes is a _single_ image.

Therefore, changing Thumbnailator to support resizing of multiple images is a 
challenge which requires changes to the underlying architecture of 
Thumbnailator.

The issue of using a single image as the unit of work in Thumbnailator is 
actually an obstacle for other reported issue (Issue 1) so if it is be 
addressed, the "fix" should also be applicable to fix other problems that 
Thumbnailator also has.

I'd imagine that creating the groundwork for enabling handling for animated 
GIFs (multiple images) will be one of the biggest changes for Thumbnailator, 
which I hope will be able to get out sometime this year.

The barrier to actually getting work done on this issue is not having a large 
enough chunk of time to "get in the zone" so to speak, to make these changes, 
due to other commitments I currently have.

Therefore, I am grateful for the offer, but the problem isn't monetary, but one 
of time and energy. (Plus, I can't make any promises that I can definitely get 
this to work.)

What will be valuable is to have resources on how to output animated GIF images 
using the Image I/O API, so that once Thumbnailator is able to write multiple 
images, I would be able to code the animated GIF output code without having to 
start research at that time.

I've created Issue 67 which will be used to gauge support for the animated GIF 
feature, and to gather resources on how to implement it.