I'm trying to clean the gallery of the iPhone, I'm sending the images that I already put in the computer to the trash. But the pics still are in the phone.
I'm an android user, so i don't know if the process is different for iPhone.
You will need to go to the "Recently Deleted" album and remove them as necessary if your iOS version > 8.1.
To remove all photos in "Recently Deleted", tap "Select" at the top and then "Delete All" at the bottom.