CNN2x alpha channel and seamless detection support

[Freestalkerdotfr]

Hello,

I'm here because I batch upscale textures and some have an alpha channel. I noticed that the alpha channel wasn't processed correctly. The alpha channel is very blurry compared to RGB channels. I also noticed that seamless textures weren't right after upscale and the textures that don't have alpha channels had been converted to RGBA where there is a slight transparency on the edge of the textures.

I hope this request will be taken into account and I thank you for your future inputs.