What algorithm does Google use to compress images (Pagespeed test)?

Question

Images

In the Pagespeed test, I get warnings that the pictures are not optimized, although they are crap optimized. For the sake of the test, I put the super-killed compressed in the script imageminand still an error

imagemin([`images/*`], 'optimized', {
  plugins: [
    mozjpeg({quality: 30, progressive: true})
  ]
})

What does he not like? There, the picture is almost invisible, some pixels are cloudy from compression.

Answer 1

it's about the fact that the declared visible area is much smaller than the actual size of the picture, in pixels