On 2010-03-15 15:49-0700 David MacMahon wrote: > > On Mar 15, 2010, at 14:32 , Alan W. Irwin wrote: > >> Then "display -immutable test_transparent.png" >> >> really does show the desktop underneath the plot which indeed is a >> really cool-looking effect. > > Using a very recent ImageMagick (6.6.0), "display" gives me the checkerboard > background without the "-immutable" option and a black background with that > option when looking at an image with a transparent background. This might be > an X server limitation or window manager limitation, but it shows that this > feature is not universally available.
Please be explicit about exactly what you did because our devices other than the three different svg ones are producing bad transparent background results that depend very much on details. Is this a -bg ffffff_0.0 result from -dev pngcairo or -dev pngqt with black transformed to transparent using "convert -transparent black ..."? Note, the -convert black option will not work if you use ffffff_0.1 because the (bad) mixed opaque colour background result produced by -dev pngcairo is no longer black in this case. My imagemagick version is 7:6.3.7.9.dfsg2-1~lenny3. I think that translates to 6.3.7 for the upstream version so it is much older than yours. Therefore, I assume this is not an ImageMagick issue. My two different Linux X servers (one for very old equipment with embedded SiS video that has a reverse-engineered 2D-only driver for that hardware) both give transparent results for the display -immutable option in that case, but do not give that result in any other case (including SVG where our three SVG devices produce correct results). From my reading there are transparency limitations to the X server on Mac OS X so perhaps that is what you are running into in the (corrected) -dev pngcairo case. > >> (Without that -immutable option, display replaces a transparent background >> with a checkerboard background which apparently is something of an industry >> standard to signal you really do have a transparent background.) > > I agree that this *can be* a really cool-looking effect, but IMHO it can also > be a really annoying/confusing looking effect (depending on what's > underneath/behind). I think it would be nice to provide the user the ability > to choose how transparent backgrounds are rendered (i.e. either "see-through" > to windows underneath/behind or use a predefined opaque background, e.g. > checkerboard). This would not be a good idea for file devices. There, you want the user running the file viewing application (say with something like the "display -immutable" option) to control how transparent backgrounds are rendered. In the separate case of interactive devices we should probably just follow what is done by the underlying external stack of libraries (such as the pango/cairo stack of libraries for -dev xcairo and the Qt4 stack of libraries for -dev qtwidget). Of course, if that external stack of libraries does offer the option of rendering transparent backgrounds as checkerboard (which I believe from my reading is a de facto standard started by Adobe photoshop) or as actually transparent for interactive devices, then it makes sense to give PLplot users interactive control over that choice via a driver option. Anyhow, our current list of devices that treat transparent background properly is limited to just svg, svgcairo, and svgqt as far as I can tell. I hope we can soon expand that list both to the xcairo and qtwidget interactive devices as well as many other file devices. Alan __________________________ Alan W. Irwin Astronomical research affiliation with Department of Physics and Astronomy, University of Victoria (astrowww.phys.uvic.ca). Programming affiliations with the FreeEOS equation-of-state implementation for stellar interiors (freeeos.sf.net); PLplot scientific plotting software package (plplot.org); the libLASi project (unifont.org/lasi); the Loads of Linux Links project (loll.sf.net); and the Linux Brochure Project (lbproject.sf.net). __________________________ Linux-powered Science __________________________ ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Plplot-devel mailing list Plplot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/plplot-devel
