Animated image overlay

• Choose the base animated GIF, APNG or WebP.
• Choose a static or animated overlay, placement, width, opacity, time range and playback behavior.
• Choose output format and total plays, compose, preview and download the animation and timing manifest.

Place a partially transparent PNG logo over every frame, or synchronize a second animation within a chosen interval.

• Animated GIF, APNG and WebP inputs are fully composited with their blend/disposal rules before editing. APNG support is non-interlaced 1–8-bit grayscale/palette or eight-bit RGB/RGBA; re-save 16-bit and Adam7 files first. Animated WebP requires a browser with ImageDecoder support.
• At most 20 MiB total input, four files, 4096 pixels per side, four megapixels per frame, 20 million decoded input canvas pixels, 20 million output canvas pixels and 300 output frames. Output is at most 40 MiB; one cycle is at most five minutes. The cancellable worker has a 120-second overall deadline.
• One source cycle is used per input. Cumulative source boundaries round to milliseconds; zero stored delays become 100 ms. GIF output rounds cumulative boundaries to 10 ms and rejects any collapsed visible interval. Very short delays may still be clamped by viewers.
• APNG retains composited eight-bit RGBA samples; GIF thresholds alpha at 128 and reduces each frame to at most 255 opaque colors; WebP RGB is lossy at every quality level while alpha is retained. Metadata and source profiles are not copied. Downloaded timing JSON explains output delays and loop semantics.
• The overlay may be static PNG/JPEG/WebP or animated GIF/APNG/WebP. Position and width must fit the base canvas; width zero retains original overlay dimensions. Scaling uses nearest-neighbor sampling and straight-alpha source-over compositing.
• The base supplies one output cycle. The overlay starts at the selected time and ends at the exclusive end time (zero means base-cycle end). Hold keeps its last frame after one cycle; repeat restarts its cycle until the overlay interval ends. The overlay input loop flag is intentionally replaced by this explicit policy.