[underlines]

if it may benefit anyone, i used this simple batch file to test out the lower bound -quality 84 with drag and drop of one/multiple images on win 86-64:

  echo Drag and drop one or multiple jpg or png files onto this batch file, to compress with google guetzli using a psychovisual model
  if [%1]==[] goto :eof
  :loop
  echo compressing...
  guetzli_windows_x86-64.exe -quality 84 %1 "%~dpn1_guetzlicompressed%~x1"
  shift
  if not [%1]==[] goto loop
  echo DONE

i'm concerned about the color changes that are clearly visible throughout the whole image.

[JyrkiAlakuijala]

Guetzli runs the whole image to the same specified quality -- when artefacts start to emerge, they are everywhere, not just in one sensitive area. Guetzli can be more likely worth its cpu cost at a higher quality, around 92-96.