This is a free and open-source Pixelorama extension that add basic Skeletal animation capabilities to the software. The source code for this extension is hosted on Github

Showcase:

You can try this extension out on the demo Pixelorama projects shown below (Click the Image)

Laser Gun	Robot	Snake

Capabilities:

1. Basic movement: You can move any bone in the skeleton and it's children will move with it.
2. Bone Chaining: In chaining mode you are only allowed to rotate a bone. the children of the bones move with parent bone but preserve their rotation.
3. Inverse Kinematics: Along with chaining, this extension also provides support for inverse kinematics, making use of the CCDIK and FABRIK algorithms.
4. Tweening Support: Gererate In-Betweens from a chosen start frame to the current frame.
5. Draw <=> Pose Mode: You can switch between the two views with ease.
6. Quick set bones: You can quickly place bones to roughly over their intended sprites with a single click.
7. Export skeleton data for manual tinkering or for use in other projects

Limitations:

1. Undo/Redo for bones is not present, though you can still Undo/Redo the usuall actions of Pixelorama.
2. There can be only ONE Pose Layer per project.

How to use:

After Importing and enabling the extension, you will get access to:

• The Skeleton tool 
• Two new options in Project menu called (Load Skeleton and Assign Pose Layer)
• A .skeletor export option

The bones assigned to groups (Arrange Groups as Bones in a skeleton), so to make a skeleton, simply make up the structure using multiple Group Layers. After this make a new Pixel Layer at the "Top" of all layers, then select it and choose Project > Assign Pose Layer. This Layer will be used to render the final "pose" of the frame.

Note: If bones do not appear after assigning a Pose Layer, please click another layer and then back to the Pose Layer.

Controls (parts of the bone):

Movement	Rotation

each bone is made up of 3 parts;

• The bigger circle is the pivot, the image of the bone will rotate around this pivot. The pivot is set by hovering over the circle then hold (Ctrl + Left/Right click) key and move the mouse. Also, moving the pivot using (Left/Right click) will move the image instead of setting pivot.
• Smaller circle controls rotation. Hold (Ctrl + Left/Right click) with mouse movement to move the circle without rotating the image (this is just to move it somewhere more comfortable). Holding (Left/Right click) and mouse movement Will rotate image.
• The solid line joining the two circles does the same as the above (however the width of the line won't change this time).