Add More Options For pngquant

[dirceu-jr]

I did some trial and error on using pngquant through this Ruby gem (image_optim) and through command line and how its results compare to TinyPNG/Kraken/ImageAlpha+ImageOptim.

It seems to me that these tools use a custom value on the --floyd option of pngquant. The manual page says about --floyd: Set dithering level using fractional number between 0 (none) and 1 (full, the default).

So through this Pull Request I add the possibility to define a custom value for the --floyd option.

I also added the possibility to use --nofs and --strip options.

[toy]

Thank you for contribution!

Just started checking and pngquant --help says nothing about --floyd switch 🤷
I need to check how this affects losslessness of optimisation, as maybe it is better to mark pngquant as lossy by default.

Please don't change version in gemspec, this always goes as a separate commit.

[dirceu-jr]

Thank you for contribution!

Just started checking and pngquant --help says nothing about --floyd switch 🤷 I need to check how this affects losslessness of optimisation, as maybe it is better to mark pngquant as lossy by default.

Please don't change version in gemspec, this always goes as a separate commit.

Check man pngquant