Add Grayscale8 and Alpha8 formats to QImage and drawing

Extend the QImage format with two 8-bit grayscale and alpha formats.
These formats have the advantage over Indexed8 that they have simpler
conversion and can be rendered to by the raster engine.

[ChangeLog][QtGui][QImage] Added support grayscale and alpha 8-bit
formats which can also be rendered to.

Change-Id: I4343c80a92a3dda196aa38d0c3ea251b094fc274
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>

1 files changed, 18 insertions, 0 deletions

diff --git a/src/gui/kernel/qpixelformat.cpp b/src/gui/kernel/qpixelformat.cpp
index 90ab2db93e..c22fd28681 100644
--- a/src/gui/kernel/qpixelformat.cpp
+++ b/src/gui/kernel/qpixelformat.cpp
@@ -77,6 +77,7 @@ QT_BEGIN_NAMESPACE
     \enum QPixelFormat::ColorModel
 
     This enum type is used to describe the color model of the pixelformat.
+    Alpha was added in 5.5.
 
     \value RGB The color model is RGB.
 
@@ -94,6 +95,8 @@ QT_BEGIN_NAMESPACE
     \value HSV The color model is HSV.
 
     \value YUV The color model is YUV.
+
+    \value Alpha There is no color model, only alpha is used.
 */
 
 /*!
@@ -290,6 +293,21 @@ QT_BEGIN_NAMESPACE
 */
 
 /*!
+    \fn QPixelFormat qPixelFormatAlpha(uchar channelSize,
+                                           QPixelFormat::TypeInterpretation typeInterpretation = QPixelFormat::UnsignedInteger)
+    \relates QPixelFormat
+    \since 5.5
+
+    Constructor function for creating an Alpha format. A mask format can be
+    described by passing 1 to \a channelSize. Its also possible to define very
+    accurate alpha formats using doubles to describe each pixel by passing 8
+    as \a channelSize and FloatingPoint as \a typeInterpretation.
+
+    \sa QPixelFormat::TypeInterpretation
+*/
+
+
+/*!
     \fn QPixelFormat qPixelFormatCmyk(uchar channelSize,
                                       uchar alphaSize = 0,
                                       QPixelFormat::AlphaUsage alphaUsage = QPixelFormat::IgnoresAlpha,