evas image might have a better quaility if scaling/transform is not necessary,
so we have a condition to check if image is axis-aligned transformed or not.
On the other hand sub-pixel(floating point coordinates unit) rendering necessary
if image has an effect such a zooming. This would result in a smoother effect
than integer coodinate system.
We need a more precise condition to confirm this,
so we intrduce "anti-alias" option to decide the condition.
now, anti-aliased objects will have a sub-pixel rendering always.