So I downloaded libwebp-0.1.3-windows-x86.zip, there is cwebp.exe inside.
I can't figure out how to compress PNGs losslessly into WebP.
These are the options it gives:
Usage:
cwebp [-preset ] [options] in_file [-o out_file]
If input size (-s) for an image is not specified, it is assumed to be a PNG or JPEG file.
Windows builds can take as input any of the files handled by WIC
options:
-h / -help ............ short help
-H / -longhelp ........ long help
-q ............. quality factor (0:small..100:big)
-preset ....... Preset setting, one of:
default, photo, picture,
drawing, icon, text
-preset must come first, as it overwrites other parameters.
-m ............... compression method (0=fast, 6=slowest)
-segments ........ number of segments to use (1..4)
-size ............ Target size (in bytes)
-psnr .......... Target PSNR (in dB. typically: 42)
-s ......... Input size (width x height) for YUV
-sns ............. Spatial Noise Shaping (0:off, 100:max)
-f ............... filter strength (0=off..100)
-sharpness ....... filter sharpness (0:most .. 7:least sharp)
-strong ................ use strong filter instead of simple.
-partition_limit . limit quality to fit the 512k limit on
the first partition (0=no degradation ... 100=full)
-pass ............ analysis pass number (1..10)
-crop .. crop picture with the given rectangle
-resize ........ resize picture (after any cropping)
-map ............. print map of extra info.
-d .......... dump the compressed output (PGM file).
-short ................. condense printed message
-quiet ................. don't print anything.
-version ............... print version number and exit.
-noasm ................. disable all assembly optimizations.
-v ..................... verbose, e.g. print encoding/decoding times
Experimental Options:
-af .................... auto-adjust filter strength.
-pre ............. pre-processing filter