Fix reading gamma from PNGs without ICC profile

The decoding of PNG_INFO_gAMA to QColorSpace was incorrect, the PNG
gamma is the inverse of the gamma value we use. We revert it
everywhere else, just not here.

Change-Id: Ic0ae1963b2dde3004cac8a6430ddaf99e7096915
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
(cherry picked from commit de2c3ccd49cb89e0c6912da3b03705a36ef03946)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/gui/image/qpnghandler.cpp b/src/gui/image/qpnghandler.cpp
index 9943e7261a..c013a06813 100644
--- a/src/gui/image/qpnghandler.cpp
+++ b/src/gui/image/qpnghandler.cpp
@@ -627,10 +627,10 @@ bool QPngHandlerPrivate::readPngHeader()
             }
             if (primaries.areValid()) {
                 colorSpace = QColorSpace(primaries.whitePoint, primaries.redPoint, primaries.greenPoint, primaries.bluePoint,
-                                         QColorSpace::TransferFunction::Gamma, fileGamma);
+                                         QColorSpace::TransferFunction::Gamma, 1.0f / fileGamma);
             } else {
                 colorSpace = QColorSpace(QColorSpace::Primaries::SRgb,
-                                         QColorSpace::TransferFunction::Gamma, fileGamma);
+                                         QColorSpace::TransferFunction::Gamma, 1.0f / fileGamma);
             }
             colorSpaceState = GammaChrm;
         }