I just rechecked in my inventory to find out why there is 37.5% transparent on the highlight : the texture is centered vertically and looks thinner than the icon. (edit eeerff only because when the icon looks bigger when mouseovered...)

so if you want exactly the same look, just find a way to vertical-center it.(edit : don't mind me i'm just typing out loud) (like maybe just 18.75% toward the bottom,idk). but still it doesn't explain why they would leave this 37% transparent, there must be an easier way... (edit : i don't take that back)

now edit with the picture, what i said was totally stupid. i should have known, my coffee is still in the mug

rerere edit : something to do with this? SetAutoAdjustWrappedCoords()... no idea... but anyway the result of whatever the method is is that bottom coord of 0.625