Compression
APNG IDAT/fdAT Chunk, Streaming Deflate Replay and Disposal Method Frame-Timing Analyzer
Upload a PNG or APNG and audit the whole animation structure: PNG signature and per-chunk CRC32 checks, IHDR bit depth / color type / interlace, acTL placement and declared frame counts, every fcTL (region bounds inside the canvas, normalized delay fractions, dispose_op none/background/previous, blend_op source/over), the shared fcTL+fdAT sequence-number contract from 0, per-frame replay of the IDAT/fdAT deflate streams with exact decompressed-size verification, and disposal-semantics audit — first-frame PREVIOUS treated as BACKGROUND, zero-delay frames, loop counts, fps and compression ratios.