WebP lossy compression

WebP, lossy, compression, image

« PNG to lossy WebP » on LC RGBA (green)

pingo's pre-transform, attempt to improve quality/size where alpha 0 = green (sharp_yuv)
original cwebp -mt -q 100 -sharp_yuv pingo -webp-lossy=100
110.36 KB 68.98 KB — 0.07s 54.60 KB — 0.06s
butteraugli 9.4562911987 — 3-norm: 2.848392 1.4623720646 — 3-norm: 0.462384
ssimulacra 0.05468042 0.00212760
pingo's pre-transform, attempt to improve quality/size where alpha 0 = green
original cwebp -mt -q 100 pingo -webp-lossy=100 -nopre
110.36 KB 62.26 KB — 0.07s 52.70 KB — 0.06s
butteraugli 5.2205448151 — 3-norm: 1.432595 1.2194836140 — 3-norm: 0.443250
ssimulacra 0.02089686 0.00235245

« PNG to lossy WebP » on LC RGBA (noise)

pingo's pre-transform, attempt to improve quality/size where alpha 0 = random (sharp_yuv)
original cwebp -mt -q 100 -sharp_yuv pingo -webp-lossy=100
810.37 KB 70.23 KB — 0.12s 54.60 KB — 0.06s
butteraugli 8.1038255692 — 3-norm: 1.993268 1.4623720646 — 3-norm: 0.462384
ssimulacra 0.02028307 0.00212760
pingo's pre-transform, attempt to improve quality/size where alpha 0 = random
original cwebp -mt -q 100 pingo -webp-lossy=100 -nopre
810.37 KB 65.36 KB — 0.09s 52.70 KB — 0.06s
butteraugli 1.6278975010 — 3-norm: 0.475694 1.2194836140 — 3-norm: 0.443250
ssimulacra 0.00299318 0.00235245

higher compression

pingo's pre-transform and lazy heuristic on « cleaned alpha »
original cwebp -mt -m 6 -q 100 -sharp_yuv pingo -webp-lossy=100 -s9
328.12 KB 133.24 KB — 1.96s 133.15 KB — 0.31s
butteraugli 1.6306440830 — 3-norm: 0.709768 1.0269782543 — 3-norm: 0.418638
ssimulacra 0.00495022 0.00474499

notes

cwebp cf847cb
cwebp -q N -sharp_yuv target
pingo rc3 (22)
pingo -webp-lossy -sN target

note that this function could be work in progress and would not always perform as well as demonstrated on any samples. the lossless compression level over this transformation can be increased to get smaller filesize by using -sN:

N: from 0 to 9 — 0: fast and good compression — 9: slow, but better compression
pingo flags -sN target

machine test: CPU G1820 2.7Ghz — 1.88GB RAM — Windows 7, 32-bit