Full opacity (alpha compositing) support (for SVG and PNG)

0 votes
asked May 28, 2020 in Wanted features by The-Lu (49,760 points)
edited May 28, 2020 by The-Lu

Hello PlantUML team,

[As is it a transparent day ;) or a sunny day wink]

According to your remark on /11214:

  • Opacity is ignored (right now) in PNG export. Not sure if this will be ever added in the future
  • Shadows will probably never work with opacity settings. Right now, you have to manually disable shadowing
  • We litterally did no test at all, so your feedback is welcome :-)

And as you mentioned on a comment on /11380:

We tested opacity management...

Opacity is ignored (right now) in PNG export.

In fact no. And it's almost good… for both SVG and PNG  //[But with some special PlantUML polarized glasses cool]//

Here are some examples, with same source code but different output color!, on version 1.2020.10, from our last comment on /11214:

(click to see on PlantUML online server)
SVG outputPNG output
skinparam SequenceGroupBodyBackgroundColor 6700FF00
skinparam SequenceGroupBodyBackgroundColor 00FF0067
skinparam SequenceGroupBodyBackgroundColor 66000099

► In fact SVG is RGBA and PNG, the other, is ARGB!


  • Could you correct that, (to have the same output), in order to support full opacity (and alpha compositing) for both SVG and PNG?
  • And also make a choice (on the skinparam parameter) for PlantUML to be RGBa or aRGB?
    My preference will be RGBa (as the same as W3C and SVG).

Thanks for your work,

1 Answer

0 votes
answered Jun 2, 2020 by plantuml (279,680 points)
selected Jun 25, 2020 by The-Lu
Best answer
That's funny result indeed :-)

We choose RGBa and this should be fixed in last beta http://beta.plantuml.net/plantuml.jar

Tell us if it's not working and a big thank you for your detailled tests and reports !