Bad UI for "Select/Deselect all" in DAM

To select/deselect all thumbnails we have a checkbox whose label changes once clicked.This is confusing (and not standard UI I suppose).
And the checkbox does not take the actuall selection into account. For example if I have a list of 4 thumbnails:

• click "select all" => the buton is labelled "Deselect all" and is checked
• Unselect manually all the thumbnails => The button stays on "Deselect all" and checked
• etc.

We should have 2 distinct buttons:

• "Select all"
• "Deselect all" (or "Unselect"?)

With a little bit of smartness:

• If the list is empty, both buttons are disabled
• If no thumbnail is selected:
  • "Select all" is enabled
  • "Deselect all" is disabled
• If all thumbnails are selected:
  • "Select all" is disabled
  • "Deselect all" is enabled
• If at least one thumbnail is selected: both buttons are enabled