Function encode_webp_animation 

pub fn encode_webp_animation(
    dimensions: (u32, u32),
    frames: &[WebpFrame<'_>],
    final_timestamp_ms: i32,
    options: WebpOptions,
    loop_count: u16,
) -> Result<Vec<u8>>

Encode complete RGBA frames concurrently and assemble an animated WebP.

This is an opt-in high-throughput path for callers that already hold every frame in memory. Unchanged pixels are omitted from later frames, while libwebp encodes independent frame rectangles in parallel through Rayon. Because frames are encoded independently, output can be materially larger than WebpEncoder’s animation-wide optimization. Use WebpEncoder for bounded memory and smaller output.