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

Question

Hello PlantUML team,

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

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 ]//

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

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

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

• https://en.wikipedia.org/wiki/RGBA_color_model
• https://developer.mozilla.org/en-US/docs/Web/CSS/color#rgba()
• https://developer.mozilla.org/en-US/docs/Web/CSS/color_value

Then:

• 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,
Regards,
Th.

Answer 1

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 !