Usually people use shape splatter nowdays . It has a companion data extract node for this. If for some reason you don't want to use shape splatter. It has very limited scale range on narrow textures 256x2048 for example . So sometimes sampler is a better choice. In such case you can use a trick of giving your inputs some…
Actually you could just make a clone of your tile sampler and make it work with inputs alphas in 8 bit mode. No need to remap anything. Sorry for over -complicating. Also you can use FXAA node to "fix" " nasty edges". That "hiden gradient" UV idea still might be useful if you want to use the leaves color counterparts…