Fixed.
It should be much better now.
Do you know why ?
Because for PNG, the quality represents a compression between 0 to 9,
Instead for JPEG, the quality is from 0 to 100 %
So only the PNG was heavy files.
In Cook, the HelperFile class abstracts it for "Quality", from 0 > 100 %
Default is 75% for JPG
Instead for PNG, the compression is set to 8 per default, almost the maximum.
So I don't know if this conversion is usefull, because 8 for PNG does not represent 75%, so the default is not the same percentage.
But this is because the compression is different.
Anyways, at the moment, the builder do not propose you that parameter, so it stays at default, but it is handled by Jdom and by the helper.
As well as rotations, filters, and so on. More to come in future, but you can already play a lot with your images.
Not thanks to me, but thanks to Joomla!
Enjoy the night. For those who live in UTC+1