Filter on portraits, landscapes (and perhaps even relative squares)

[ajslaghu]

Usecase: I am looking only for landscapes when it comes to wallpapers on my desktop.

But looking for Shower curtains I would filter on portraits.

Assuming images consist of X and Y;
X < Y (absolute portrait)
Y > X (absolute landscape)
Y == X (Absolute square)

X < aY (a=0-0.999 relative portrait)
Y < aX (a=0-0.999 relative landscape)
X >= aY && Y >= aX (relative square)

what would be factor a?
lets assume aspect ratioś should also be provided (as filter) , I would assume aspect ratios wont exceed 1 digit (34/179th, anyone?). meaning 9/10 is not correct, but 8/9 would be.
the most sqaared aspect ratio then would be 5/9 or 4/9
the result is a difference of 5.55% from 50%.
I think this is a nice margin for errors.

[breyten]

Implementation is (partiallly) done in #104 (orientation), having aspect ratios should be added.