The attached file was displayed with gs -sDEVICE=x11
mask-alpha-pdf-argb32-out.pdf. The file does not display correctly in
Ghostscript 8.60. 

The file draws a triangle and rectangle in a transparency group with an Alpha
type SMask consisting of a circle with the RGBA (0.4, 0.4, 0.4, 0.8) and the
background with RGBA (0.8, 0.8, 0.8, 0.4).

Adobe Reader 8.1.0 on Windows XP displays the file correctly with area inside
the circle drawn with alpha=0.8 mask and the area outside the circle drawn with
alpha = 0.4 mask.

Using Ghostscript 8.60 the area inside the circle is drawn with what appears to
be the alpha=0.4 mask and the area outside the circle drawn with alpha=0.8. It
looks like Ghostscript is creating the mask from the colors instead of the alpha.

Adobe Reader 7 for Linux also displays the file incorrectly.