Test an alpha VirtualDevice and fix GetPixel and DrawPixel

This adds an test for a VirtualDevice with an alpha channel,
which checks that getting a BitmapEx from the alpha VirtualDevice
is has a alpha channel properly set.

Test that using GetPixel and DrawPixel properly handle an alpha
based Color, which they didn't, so this also includes the fix for
thouse 2 methods.

Change-Id: I419b8e0f66ab5f8266c6129e501ed75ef517fd44
Reviewed-on: https://gerrit.libreoffice.org/70805
Tested-by: Jenkins
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>

vcl/qa/cppunit/bitmaprender/BitmapRenderTest.cxx

@@ -42,12 +42,14 @@ public:
     void testTdf104141();
     void testTdf113918();
     void testDrawAlphaBitmapEx();
+    void testAlphaVirtualDevice();
     void testTdf116888();
 
     CPPUNIT_TEST_SUITE(BitmapRenderTest);
     CPPUNIT_TEST(testTdf104141);
     CPPUNIT_TEST(testTdf113918);
     CPPUNIT_TEST(testDrawAlphaBitmapEx);
+    CPPUNIT_TEST(testAlphaVirtualDevice);
     CPPUNIT_TEST(testTdf116888);
 
     CPPUNIT_TEST_SUITE_END();
@@ -150,6 +152,73 @@ void BitmapRenderTest::testDrawAlphaBitmapEx()
 #endif
 }
 
+void BitmapRenderTest::testAlphaVirtualDevice()
+{
+    // Create an alpha virtual device
+    ScopedVclPtr<VirtualDevice> pAlphaVirtualDevice(VclPtr<VirtualDevice>::Create(
+        *Application::GetDefaultDevice(), DeviceFormat::DEFAULT, DeviceFormat::DEFAULT));
+
+    // Set it up
+    pAlphaVirtualDevice->SetOutputSizePixel(Size(4, 4));
+    pAlphaVirtualDevice->SetBackground(Wallpaper(COL_TRANSPARENT));
+    pAlphaVirtualDevice->Erase();
+
+    // Get a BitmapEx from the VirDev -> Colors should have alpha
+    BitmapEx aBitmap = pAlphaVirtualDevice->GetBitmapEx(Point(), Size(4, 4));
+    CPPUNIT_ASSERT_EQUAL(long(4), aBitmap.GetSizePixel().Width());
+    CPPUNIT_ASSERT_EQUAL(long(4), aBitmap.GetSizePixel().Height());
+    Color aColor = aBitmap.GetPixelColor(1, 1);
+    CPPUNIT_ASSERT_EQUAL(Color(0xff, 0xff, 0xff, 0xff), aColor);
+
+    // Draw an opaque pixel to the VirDev
+    pAlphaVirtualDevice->DrawPixel(Point(1, 1), Color(0x00, 0x22, 0xff, 0x55));
+
+    // Read back the opaque pixel
+#ifdef MACOSX
+    // Oh no.. what we input is not the same as what we get out!
+    CPPUNIT_ASSERT_EQUAL(Color(0x00, 0x2C, 0xff, 0x44), pAlphaVirtualDevice->GetPixel(Point(1, 1)));
+#else
+    CPPUNIT_ASSERT_EQUAL(Color(0x00, 0x22, 0xff, 0x55), pAlphaVirtualDevice->GetPixel(Point(1, 1)));
+#endif
+
+    // Read back the BitmapEx and check the opaque pixel
+    aBitmap = pAlphaVirtualDevice->GetBitmapEx(Point(), Size(4, 4));
+    CPPUNIT_ASSERT_EQUAL(long(4), aBitmap.GetSizePixel().Width());
+    CPPUNIT_ASSERT_EQUAL(long(4), aBitmap.GetSizePixel().Height());
+
+    aColor = aBitmap.GetPixelColor(1, 1);
+#ifdef MACOSX
+    // Oh no.. what we input is not the same as what we get out!
+    CPPUNIT_ASSERT_EQUAL(Color(0x00, 0x2C, 0xff, 0x44), aColor);
+#else
+    CPPUNIT_ASSERT_EQUAL(Color(0x00, 0x22, 0xff, 0x55), aColor);
+#endif
+
+    // Draw an semi-transparent pixel
+    pAlphaVirtualDevice->DrawPixel(Point(0, 0), Color(0x44, 0x22, 0xff, 0x55));
+
+    // Read back the semi-transparent pixel
+#ifdef MACOSX
+    // Oh no.. what we input is not the same as what we get out!
+    CPPUNIT_ASSERT_EQUAL(Color(0x34, 0x2C, 0xFF, 0x44), pAlphaVirtualDevice->GetPixel(Point(0, 0)));
+#else
+    CPPUNIT_ASSERT_EQUAL(Color(0x44, 0x22, 0xFF, 0x55), pAlphaVirtualDevice->GetPixel(Point(0, 0)));
+#endif
+
+    // Read back the BitmapEx and check the semi-transparent pixel
+    aBitmap = pAlphaVirtualDevice->GetBitmapEx(Point(), Size(4, 4));
+    CPPUNIT_ASSERT_EQUAL(long(4), aBitmap.GetSizePixel().Width());
+    CPPUNIT_ASSERT_EQUAL(long(4), aBitmap.GetSizePixel().Height());
+
+    aColor = aBitmap.GetPixelColor(0, 0);
+#ifdef MACOSX
+    // Oh no.. what we input is not the same as what we get out!
+    CPPUNIT_ASSERT_EQUAL(Color(0x34, 0x2C, 0xFF, 0x44), aColor);
+#else
+    CPPUNIT_ASSERT_EQUAL(Color(0x44, 0x22, 0xFF, 0x55), aColor);
+#endif
+}
+
 void BitmapRenderTest::testTdf116888()
 {
     // The image is a 8bit image with a non-grayscale palette. In OpenGL mode

vcl/source/outdev/pixel.cxx

@@ -32,20 +32,26 @@
 #include <outdata.hxx>
 #include <salgdi.hxx>
 
-Color OutputDevice::GetPixel( const Point& rPt ) const
+Color OutputDevice::GetPixel(const Point& rPoint) const
 {
     Color aColor;
 
-    if ( mpGraphics || AcquireGraphics() )
+    if (mpGraphics || AcquireGraphics())
     {
-        if ( mbInitClipRegion )
+        if (mbInitClipRegion)
             const_cast<OutputDevice*>(this)->InitClipRegion();
 
-        if ( !mbOutputClipped )
+        if (!mbOutputClipped)
         {
-            const long nX = ImplLogicXToDevicePixel( rPt.X() );
-            const long nY = ImplLogicYToDevicePixel( rPt.Y() );
-            aColor = mpGraphics->GetPixel( nX, nY, this );
+            const long nX = ImplLogicXToDevicePixel(rPoint.X());
+            const long nY = ImplLogicYToDevicePixel(rPoint.Y());
+            aColor = mpGraphics->GetPixel(nX, nY, this);
+
+            if (mpAlphaVDev)
+            {
+                Color aAlphaColor = mpAlphaVDev->GetPixel(rPoint);
+                aColor.SetTransparency(aAlphaColor.GetBlue());
+            }
         }
     }
     return aColor;
@@ -90,7 +96,7 @@ void OutputDevice::DrawPixel( const Point& rPt, const Color& rColor )
     if ( mpMetaFile )
         mpMetaFile->AddAction( new MetaPixelAction( rPt, aColor ) );
 
-    if ( !IsDeviceOutputNecessary() || ImplIsColorTransparent( aColor ) || ImplIsRecordLayout() )
+    if ( !IsDeviceOutputNecessary() || ImplIsRecordLayout() )
         return;
 
     Point aPt = ImplLogicToDevicePixel( rPt );
@@ -106,8 +112,11 @@ void OutputDevice::DrawPixel( const Point& rPt, const Color& rColor )
 
     mpGraphics->DrawPixel( aPt.X(), aPt.Y(), aColor, this );
 
-    if( mpAlphaVDev )
-        mpAlphaVDev->DrawPixel( rPt );
+    if (mpAlphaVDev)
+    {
+        Color aAlphaColor(rColor.GetTransparency(), rColor.GetTransparency(), rColor.GetTransparency());
+        mpAlphaVDev->DrawPixel(rPt, aAlphaColor);
+    }
 }
 
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