correct name of 'category' for picture is in subcategory

[Hello-world]

I wanted to place more correct name of category for picture (in description, in toplist and everywhere ).
If image are in subcategory, like ' Home / cat1 / subcat2 / pic1 ', the category name should sound ' cat1: subcat2 ', instead of just ' subcat2 '
How can I do it? Thx