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Details

Type: Bug
Resolution: Done
Priority: P3: Somewhat important
Fix Version/s: 5.15.1, 6.0.0
Affects Version/s: 5.12.9, 5.15.0 RC
Component/s: GUI: Painting
Labels:
None
Environment:
Windows 10

Platform/s:

All
Commits:
0e526ed3f93f9aab1f499f80d703fc4e93314223 (qt/qtbase/5.15)

Description

It appears Qt is using different policy when convert color component.

In most of the code it is using qRound to calculate different component, but for integral value it is using floor to get the component (in unsigned short fixed point). That result in some weird result, for example:

auto hsl = QColor::fromHslF(179 / 360.0, 62 / 100.0, 37 / 100.0);
auto rgb = hsl.toRgb();
qDebug() << "hsl:" << hsl;
qDebug() << "rgb:" << rgb;
qDebug() << "rf:" << rgb.redF() * 255 << "gf:" << rgb.greenF() * 255 << "bf:" << rgb.blueF() * 255;
qDebug() << "ri:" << rgb.red() << "gi:" << rgb.green() << "bi:" << rgb.blue();

that prints:

hsl: QColor(AHSL 1, 0.497222, 0.620005, 0.370001) 
rgb: QColor(ARGB 1, 0.140597, 0.599405, 0.59176)
rf: 35.8521 gf: 152.848 bf: 150.899
ri: 35 gi: 153 bi: 151

as you can see 35.8521 becomes 35, while 152.848 becomes 153