PNG Codec Benchmarks

A from-scratch PNG codec in Rust - blazediff-png - against spng , image-rs (png), and zune-png . Decode and encode are timed (best-of, size-scaled iteration counts) over the full fixture corpus (34 PNGs, 342.7 MPx), single-threaded on Apple Silicon. Lower is better.

Encode is measured at two settings so the speed/size trade-off is explicit and zune’s stored-only encoder is compared fairly: no compression (stored deflate blocks) and half compression (half of each codec’s own max deflate level - libdeflate 12 → 6, zlib 9 → 4).

Decode

blazediff decodes ~1.39× faster than spng across the corpus.

Encode - No Compression

Levels: blazediff stored · spng stored · image-rs stored · zune stored.

blazediff encodes ~2.20× faster than spng (stored) across the corpus.

Encode Size - No Compression

Output bytes per codec; the final row is each codec’s total as a percentage of spng’s (the de-facto reference). zune-png has no compressed mode, so it always writes stored output - far larger than the rest.

Encode - Half Compression

Levels: blazediff libdeflate 6 · spng zlib 4 · image-rs flate2 4 · zune stored.

blazediff encodes ~3.83× faster than spng (zlib 4) across the corpus.

Encode Size - Half Compression

Output bytes per codec; the final row is each codec’s total as a percentage of spng’s (the de-facto reference). zune-png has no compressed mode, so it always writes stored output - far larger than the rest.