Generate smaller and compressed versions of images

[n-peugnet]

Todo

• Along with full size images, generate lighter versions of big pictures (and a link from the smaller one to the original). Parameter to configure the size after which optimized versions are generated.

• Convert all baseline jpeg images into progressive ones.
  from Wikipedia:

  It is also possible to transform between baseline and progressive formats without any loss of quality, since the only difference is the order in which the coefficients are placed in the file.

  Google engineers think this is a bad idea :

  WebP does not offer a progressive or interlaced decoding refresh in the JPEG or PNG sense. This is likely to put too much pressure on the CPU and memory of the decoding client as each refresh event involves a full pass through the decompression system.

  On average, decoding a progressive JPEG image is equivalent to decoding the baseline one 3 times.

• Maybe convert png images into webp combined with HTML 5 picture fallback

Useful links for images formats:

• https://developer.mozilla.org/en-US/docs/Learn/Performance/Multimedia

[n-peugnet]

What do you think about this @vincent-peugnet ?