[vladdanilov]

It's pretty good. The problem with automatic lossy compression is consistent quality.

There is a number of issues with each and every tool you mentioned, e.g. color information stripped with metadata causing color shifts in wide-gamut and non-sRGB images, camera images changing orientation when Exif stripped, color banding on PNGs and JPEGs even when using Guetzli (JPEGmini is not nearly as good in other cases, but Guetzli is extremely slow), unexpected dithering noise on flat PNGs, tracing artefacts on screen recorded GIFs, JPEGs being overcompressed, poor lossless compression (virtually any online service), progressive JPEGs incompatible with Photoshop, etc.

These are just some of the problems I've been solving, and yes, there are better tools.

[acconrad]

How are you getting around those issues? Very interesting! I only saw issues w stripping metadata on JPEGs (same issues you saw).

[vladdanilov]

The only solution I found is to build a new tool, and that required a complete rewrite of existing optimizers and significant changes to underlying libraries.

[acconrad]

But can't you choose the compression algorithm in those tools? I know you can in ImageOptim and JpegMini...

[vladdanilov]

It's not automatic then, which is critical for batch processing, and does not solve all the problems, and create new usability problems for most users.