Questions and postings pertaining to the usage of ImageMagick regardless of the interface. This includes the command-line utilities, as well as the C and C++ APIs. Usage questions are like "How do I use ImageMagick to create drop shadows?".
Your alpha channel is totally white. So no transparency anywhere. You need to make a (b/w or grayscale) mask to cut out the parts you don't want and then overlay that on your base image.
I would start by turning white into a masking image. then mody that mask by removing any pixel that is down and left of another pixel in the mask! that will remove the 'shadow'