vcl: recolor images (icons) to be more visible in a dark theme

This adds recoloring of images/icons (suited for breeze and sifr)
so they are more visible when a dark theme is used (for example gtk3
can switch to a dark theme). LO must be started with environment
variable VCL_ICONS_FOR_DARK_THEME set to 1.

open issues - currently all images/icons are recolored but not all
images should get recolored.

Change-Id: Ibc42e30af79bb4c4f04c67b760019311b97b2cc6

3 files changed, 66 insertions, 0 deletions

diff --git a/vcl/Library_vcl.mk b/vcl/Library_vcl.mk
index f95a999c4a1b..f2cd719a4e27 100644
--- a/vcl/Library_vcl.mk
+++ b/vcl/Library_vcl.mk
@@ -318,6 +318,7 @@ $(eval $(call gb_Library_add_exception_objects,vcl,\
     vcl/source/bitmap/bitmapscalesuper \
     vcl/source/bitmap/BitmapSymmetryCheck \
     vcl/source/bitmap/BitmapFilterStackBlur \
+    vcl/source/bitmap/BitmapProcessor \
     vcl/source/bitmap/checksum \
     vcl/source/helper/canvasbitmap \
     vcl/source/helper/canvastools \
diff --git a/vcl/source/bitmap/BitmapProcessor.cxx b/vcl/source/bitmap/BitmapProcessor.cxx
new file mode 100644
index 000000000000..e9d36ed53539
--- /dev/null
+++ b/vcl/source/bitmap/BitmapProcessor.cxx
@@ -0,0 +1,58 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ */
+
+#include <vcl/BitmapProcessor.hxx>
+#include <vcl/bmpacc.hxx>
+#include <basegfx/color/bcolortools.hxx>
+
+BitmapEx BitmapProcessor::createLightImage(const BitmapEx& rBitmapEx)
+{
+    const Size aSize(rBitmapEx.GetSizePixel());
+
+    Bitmap aBitmap(rBitmapEx.GetBitmap());
+    Bitmap aDarkBitmap(aSize, 24);
+
+    BitmapReadAccess* pRead(aBitmap.AcquireReadAccess());
+    BitmapWriteAccess* pWrite(aDarkBitmap.AcquireWriteAccess());
+
+    if (pRead && pWrite)
+    {
+        for (int nY = 0; nY < aSize.Height(); ++nY)
+        {
+            for (int nX = 0; nX < aSize.Width(); ++nX)
+            {
+                BitmapColor aColor = pRead->HasPalette() ?
+                                        pRead->GetPaletteColor(pRead->GetPixelIndex(nY, nX)) :
+                                        pRead->GetPixel(nY, nX);
+                basegfx::BColor aBColor(Color(aColor.Invert()).getBColor());
+                aBColor = basegfx::tools::rgb2hsl(aBColor);
+
+                double fHue = aBColor.getRed();
+                fHue += 180.0;
+                while (fHue > 360.0)
+                    fHue -= 360.0;
+                aBColor.setRed(fHue);
+
+                aBColor = basegfx::tools::hsl2rgb(aBColor);
+                aColor.SetRed(((aBColor.getRed()   * 255.0) + 0.5));
+                aColor.SetGreen(((aBColor.getGreen() * 255.0) + 0.5));
+                aColor.SetBlue(((aBColor.getBlue()  * 255.0) + 0.5));
+
+                pWrite->SetPixel(nY, nX, aColor);
+            }
+        }
+    }
+    Bitmap::ReleaseAccess(pWrite);
+    Bitmap::ReleaseAccess(pRead);
+
+    return BitmapEx(aDarkBitmap, rBitmapEx.GetAlpha());
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/vcl/source/gdi/impimagetree.cxx b/vcl/source/gdi/impimagetree.cxx
index 5116a3621ec4..38cfefdb14fe 100644
--- a/vcl/source/gdi/impimagetree.cxx
+++ b/vcl/source/gdi/impimagetree.cxx
@@ -45,6 +45,8 @@
 #include "impimagetree.hxx"
 #include <vcldemo-debug.hxx>
 
+#include <vcl/BitmapProcessor.hxx>
+
 using namespace css;
 
 namespace {
@@ -123,7 +125,12 @@ bool ImplImageTree::loadImage(OUString const & name, OUString const & style, Bit
     {
         try {
             if (doLoadImage(name, aStyle, bitmap, localized))
+            {
+                static bool bIconsForDarkTheme = !!getenv("VCL_ICONS_FOR_DARK_THEME");
+                if (bIconsForDarkTheme)
+                    bitmap = BitmapProcessor::createLightImage(bitmap);
                 return true;
+            }
         }
         catch (css::uno::RuntimeException &) {}