How can I mask an image? I imported a downloaded image from CG textures that had the chequered background. I converted it from JPEG to PNG. I imported it into Blender 2.74 and later in 2.76 as an "Images as Planes" Adjusted the "Import Options" to "Use Alpha" and " "Premultiplied" and "Emission/Transparent" but it still shows the chequered background when rendered.
I also did the long way with UV unwrap and "Transparent" nodes and Alpha noodle In Image texture to Mix shader "Fac"