With the pdf i'm going to attach GPL Ghostscript SVN PRE-RELEASE 8.61 (2007-08-02) that comes with ubuntu developer version draws an empty page that is wrong.
Created attachment 3319 [details] The said pdf
With gshead (r8208) and -sDEVICE=ppmraw I get an image; it's not correct, but it's not blank.
Created attachment 3320 [details] AR7.jpg Image generated by Adobe Acrobat Reader 7
Created attachment 3321 [details] GS860.jpg Image generated by Ghostscript 8.60
Note ignore the border lines on the JPEG images -- they are a result of manual cropping of screen snapshots. The problem is in a rectangle that is filled with a PatternType 1 that is filled with an DeviceRGB Image (res5) that has an SMask (a DeviceGray Image -- object 3 0). The GS results looks like the SMask is being ignored since the part of the SMask that overlays the red triangle is gray (which should lighten the red toward white) and the lower triangle of the SMask is black which should make that part of the 'red/black' transparent (so it shows as white). This is a nice simple example. Thanks to the submitter for such a simple case. I've extracted the RGB image and the SMask and attached them as ppm and pgm files respectively.
Created attachment 3322 [details] rgb20x20.ppm
Created attachment 3323 [details] gray20x20.pgm
Changing assigment since I work in this area.
Changing assignment to Michael since he wants to work on transparency.
Verified that this is a transparency issue and does not work correctly with the softmask branch. Upon inspection I see that this has a knockout transparency group. I suspect that is where the problem lies as it is the first one I have run across.
This currently renders properly with the soft mask branch.
Fixed with merge of soft mask branch