Add Size getter for pixels and megapixels

[ezaquarii]

Number of pixels is used in some UI logic to sort available sizes. It's tedious to multiply it on each occasion. Megapixels count is useful for presentation, the same as aspect ratio.

[Diolor]

Hey @ezaquarii, thanks !

Size is meant to not have units. We actually use it everywhere as Resolution with pixels as units. Renaming this to Resolution will create breaking changes. Renaming docs only (about the units) and keeping the Size name will feel incomplete.

So let's keep only the width * height operation under the name getArea().

Fun fact: According to google 1MP = 1,048,576 pixels :D

[ezaquarii]

Fair enough. Here you go.

[Diolor]

Thanks!