Pieces: Convert PNG pieces to Webp

[SergioGlorias]

Notes:

• "mono" pieces is used? need for chessground? deleted
• "Disguised" pieces is same image in all pieces: setted all to w.webp and b.webp
• updated script to use webp

comparison:

assets/piece_sets

• Before PR: 24,1 MiB (25 255 764)
• After PR: 11,2 MiB (11 787 338) (-53.33% 📉)

[veloce]

@SergioGlorias I think 'mono' can be removed yes.

This is still in draft, shall I wait to test that or is it good now?

[SergioGlorias]

@veloce still has 14-piece sets to do.

[veloce]

@SergioGlorias how are you converting the pieces? From png to webp or from svg? It would be nice to update the script that currently convert to png, to make it convert to webp.

[SergioGlorias]

@veloce, I'm using https://squoosh.app to convert
Right now I'm working directly with the PNGs for a better comparison.
Regarding the script: the times I made scripts for Lila's stuff, I had to convert from SVG to PNG and then convert to WEBP.
Another issue is that I can manually adjust things that I can only improve by seeing them (like reducing the color palette for simple images).

[veloce]

I see. Thanks for the explanation, and for all the converting work!

We don't need to update the script right now, but it will be useful when we want to add a new piece set.

Do you think it is easy to modify the existing script to add another convert step from PNG to WEBP?

We shall do that in another PR.