Transparency not working in cycles I have Blender 2.75 and I am working on a project. I want to import a transparent window texture but when I do this happens:



It doesn't look transparent in Blender. When I render it with a light and a green cube behind it this happens:



The bars are transparent but the background turned black. The same thing happens with another texture when I import it. The background of the texture is white and doesn't blend in with the brick texture:



How do I make these textures transparent the right way?

EDIT: When I add this node setup:



The 3rd texture (with the background not blending in) just shows all white and it's a black border when rendered.
There is no alpha channel behind the bars, just around the window.

This image shows the alpha channel you have on your image.
To make it transparent use the following node setup:



To make the black areas of the images transparent you need to edit the image on an image editor (like photoshop or gimp), or add acolor ramp to control the transparency on a new mix shader.