Thumbnail filter “wp_thumbnail_max_side_length” gone

Hi Community,

I am having real problems getting an old plugin of mine to work. I can’t find a replacement for the filter “thumbnail_max_side_length” which I used to resize thumbs to custom sizes. If I search my complete wordpress installation the filter “thumbnail_max_side_length” doesn’t even show up. That means it must have been replaced by something else….?

I know I can set sizes in the admin, but I want to do something more complex where I have 3 different sizes and decide on upload which one to take.

Any help greatly appreciated!
Tommi