Possible to add png optimization?

I’m aware of the discussion in #3 but it seems that responsive-loader is able to optimize jpegs via the quality setting. Why is it possible to optimize jpegs but not png? Or can optipng and/or pngquant be added? I’d love to be able to handle both jpegs and pngs with this loader.

[kasvtv]

Has anyone found a good workflow for minifying the png’s that this plugin creates? It is currently quite a big problem for me, downsizing a 5kB PNG results in a 15kB PNG…

[dazuaz]

Sharp supports PNG optimization only if libvips is compiled with support for libimagequant.

It does not come as default in the bundled libvips binaries that are in the sharp npm package because:

The prebuilt binaries provided by sharp for libvips and its dependencies do not include GPL-licensed or patent-encumbered software.

_Originally posted by @lovell in https://github.com/lovell/sharp/issues/1793#issuecomment-512346455_

To optimize all png images that webpack emits you can use a plugin like imagemin-webpack:

npm install imagemin-webpack imagemin imagemin-pngquant

// webpack config
...
  plugins: [
    new ImageminPlugin({
      test: /\.(png)$/i,
      bail: false, // Ignore errors on corrupted images
      cache: true,
      imageminOptions: {
        // Before using imagemin plugins make sure you have added them in `package.json` (`devDependencies`) and installed them
        // Lossy optimization, check the documentation for other options. 
        plugins: [
          [
            "pngquant",
            {
              quality: [0.6, 0.8],
            },
          ],
        ],
      },
      loader: false,
    }),
  ],
...