Created attachment 6863 [details] Wline_BB.pdf The attached PDF file has a White line in the middle of the image when run with: gs -r600 -sDEVICE=png16m -o wline.png Wline_BB.pdf
Created attachment 6864 [details] cutdown.pdf A more cutdown version of the file.
As might be expected from looking at the file, the image with the line in it is in fact 2 images that are supposed to be displayed abutting one another. The top image starts at 4541.67 and goes upwards. The bottom image starts at 4118.67 and extends upwards for a height of 446. At first glance therefore the two images therefore overlap and there should be no white line. In fact, the bottom image is masked. Both the image and its mask are 75 pixels high, and the top 5 pixels in the image are entirely masked out. This means that 'painting' portion of that image will extend upwards by 446*70/75 pixels = 416.266667 pixels. Thus we expect the bottom image to cover from 4118.67 to 4534.93667. This leaves a gap between 4534.93 and 4541.67, which is manifested in the rendering as a blank line. I think gs is doing the right thing here...
Acrobat 9 Pro gives the same white line when exported to a TIFF at 600dpi. It gives *worse* white lines when rendered to the screen. So I don't think this bug is valid.