Magento media cache url

When images are uploaded, they are resized and put into diffent cache folders.
“pub/media/catalog/product/cache/1cd59219f95f9c415e6b76e445689a097/J/K/JK791735.jpg” ect..

Where in Magento is that current cache folder/hash stored? (“1cd59219f95f9c415e6b76e445689a097”)

Is it calculated somehow? Stored i DB? Stored in a ini file somewhere?