Consider this document: attachment 112798 [details] (it discusses another bug, but that's not important). In that document, we have a table. All table cells' text color is Automatic. Some of these table cells have background color RGB = (0,255,0), i.e. full Green with no Red or Blue. LibreOffice choose White for the text color in this case. However - White is a poor choice here: Ihas a lot less contrast, with this kind of Green (which, btw, has a brightness value of 100%); Black would have been a much better choice. Not sure what the color choice logic is, but its result in this case is off.
Confirm. In Writer, but also copied the table from Writer to Calc. Where for see also bug 156182 at 24.2.0 the luminance/contrast threshold was adjusted. Yet in Calc the Automatic formatting for text on a 0,255,0 bg cell remains white. So are we just not testing the luminance contrast threshold in appropriate fashion? Or do the IsDark() / IsLight() GetLuminance() ranges for RGB greens somehow in need a different test? @Heiko? Version: 24.8.0.0.alpha0+ (X86_64) / LibreOffice Community Build ID: 30c6e51fc9cb0fa864e1755271343d847fcced25 CPU threads: 8; OS: Windows 10.0 Build 19045; UI render: Skia/Raster; VCL: win Locale: en-US (en_US); UI: en-US Calc: CL threaded
(In reply to V Stuart Foote from comment #1) Thanks. Indeed, the behavior is the same in Calc, and I had forgotten to mention I was using: Version: 24.2.0.2 (X86_64) / LibreOffice Community Build ID: b1fd3a6f0759c6f806568e15c957f97194bbec8f CPU threads: 4; OS: Linux 6.6; UI render: default; VCL: gtk3 Locale: en-IL (en_IL); UI: en-US I should also say, that the "problem" is not with the Brightness value I mentioned earlier; for Red, i.e. RGB = (255,0,0), the use of White text is fine, and probably even a little better than Black. It's also not about Luminance/Lightness, in the HSL model, since for both Red and Green, the L value is 50%.
Obviously an issue with the luminance calculation and/or the used threshold for dark. I suggest to discuss this topic on bug 156182.