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Correct compositionMode documentation

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Most composition modes require an alpha-channel to be meaningful, but
not all, and there is no requirements of specific formats.

Change-Id: I11e930ccc07e9ff5df06dbda6745e4afb79f5e08
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>
This commit is contained in:
Allan Sandfeld Jensen 2016-04-27 11:53:16 +02:00 committed by Allan Sandfeld Jensen
parent ffd99e1d18
commit 3cae115d6d
1 changed files with 4 additions and 5 deletions
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9
src/gui/painting/qpainter.cpp
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@ -2182,11 +2182,10 @@ void QPainter::setBrushOrigin(const QPointF &p)
destination pixel in such a way that the alpha component of the
source defines the translucency of the pixel.
When the paint device is a QImage, the image format must be set to
\l {QImage::Format}{Format_ARGB32_Premultiplied} or
\l {QImage::Format}{Format_ARGB32} for the composition modes to have
any effect. For performance the premultiplied version is the preferred
format.
Several composition modes require an alpha channel in the source or
target images to have an effect. For optimal performance the
image format \l {QImage::Format}{Format_ARGB32_Premultiplied} is
preferred.
When a composition mode is set it applies to all painting
operator, pens, brushes, gradients and pixmap/image drawing.