AFAIK .gif image loading support (and by extension .gif animations) are not possible in Fusion 9's version of UI Manager, so you will have to use a series of PNG format images if you want things to work.
The good news is there are some improved HTML rendering features in Fusion/Resolve v16.1+ along with the new
function that may (in time) give you an alternative workflow solution for smooth and consistent image sequence playback in your custom UIs that could play and loop forever. As always, the issue is there is a Fusion v16 scripting API documentation shortage that would be required to explain a few of the required fine details...
In the short term, for a single shot image sequence playback approach you could try loading the images one at a time via a
placed on a
, or via
field's HTML mode and control the playback rate via a "blocking" delay function like
FYI: For a Lua script that works with an image sequence made from a series of PNGs, it might be easier to use the full absolute file path to each image sequence PNG frame on disk via expanding the PathMap URL instead of doing the base64 image encoding thing. A PNG format image sequence would tend to add a lot of file size to your script as based64 data.