Tobias Sager a écrit :

I had one problem though. I have a drawing with a single image on the page. Displays fine. When saving this image to EPS, the image would get a black background. When exporting to PNG and then converting to EPS (GIMP), all works fine.

After wandering around in the sources, it seems PS output (so EPS too) can encapsulate images but currently only R G and B channels (src/extension/internals/ps.cpp, PrintPS::print_image)

since, as read in _Transparency in graphic files_ in Wikipedia (http://en.wikipedia.org/wiki/Transparency_in_graphic_files#Transparency_in_P...), we use Level 3 PostScript ( EPS headers are "%!PS-Adobe-3.0 EPSF-3.0", so I think it's level 3), it could be good to look at trying to make the pngs transparency channel available in the PS file.

[...] Level 3 PostScript adds further transparency option for any raster image. A transparent color, or range of colors, can be applied; or a separate 1-bit mask can be used to provide an alpha channel. [...]

Since I think PNG8 only have a single color marked as transparent (as transparent gifs too) this 1-bit mask could work very well for GIFs and PNG8s.

for PNG24... hum... I'm not sure it will be possible to do that since they implement a full 256 levels alpha channel if I remember well and a "range of colors" to set as transparent would not be enough... Maybe some ps engine does this well (hacks?), it could be worth checking.

mtou