Making it possible to NOT convert images that don't provide any performance gain.

[basserd]

For example I've also applied the bulk convert tool on my own theme. In this theme we use alot of .PNG icons. Some of which have a bigger size when having the .WEBP extension applied to them.

I would like a addition within the code that detects any loss of performance. And therefore not converting that image. Probably should have some sort of system which marks images that should be ignored from converting.

[Ruzgfpegk]

According to the Lossless and Transparency Encoding in WebP study, the decoding speed is on par with PNG (but it uses more memory).

As for size, they claim that "the compression density is better for more than 99% of the web images" (for "lossless VS PNG").

To me the relative unknown lies in the "near lossless" option. Is is faster than lossless? I would think it's the same (if "near lossless" is just a pre-processing and the bitstream isn't more complex because of that) or even a bit faster given that there are less bits to read, but I really don't know.

EDIT: According to Jyrki Alakuijala, one of the authors of the previously mentioned study:

In many scenarios, lossless decodes faster, but not always. Near-losslesss decodes faster than lossless. Delta palettization or palettized lossless decode even faster than -near_lossless.