Cannot retrieve dimensions from a PNG if read through ApngDecoder because of a missing trait

[amyspark]

This happens in image-rs 0.25.9

Expected

I'm relying on the decoders supporting both AnimationDecoder and ImageDecoder traits in order to query image dimensions and then extract the individual frames for downstream consumption.

Actual behaviour

This is the case for GifDecoder and WebpDecoder, but not for ApngDecoder. The latter exposes animation frames, but not the dimensions, so for that particular format I cannot broadcast the information to the rest of the pipeline.

I think this can be fixed by simply forwarding the relevant trait functions to the underlying decoder.

Reproduction steps

Clone and cargo build the following repo: https://github.com/amyspark/imagers-apng-test.git

See https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/2856 for further context.