Add ability to change tint/shade of a color.

Change-Id: I6933393732d23fe9386cb8b768676887c026bd39

include/tools/color.hxx

@@ -161,6 +161,16 @@ public:
     void IncreaseLuminance(sal_uInt8 cLumInc);
     void DecreaseLuminance(sal_uInt8 cLumDec);
 
+    /**
+     * Apply tint or shade to a color.
+     *
+     * The input value is the percentage (in 100th of percent) of how much the
+     * color changes towards the black (shade) or white (tint). If the value
+     * is positive, the color is tinted, if the value is negative, the color is
+     * shaded.
+     **/
+    void ApplyTintOrShade(sal_Int16 n100thPercent);
+
     void DecreaseContrast(sal_uInt8 cContDec);
 
     void Invert();

tools/source/generic/color.cxx

@@ -29,6 +29,8 @@
 #include <tools/rcid.h>
 #include <tools/resid.hxx>
 #include <tools/rc.h>
+#include <tools/helpers.hxx>
+#include <basegfx/color/bcolortools.hxx>
 
 static inline long _FRound( double fVal )
 {
@@ -113,6 +115,34 @@ bool Color::IsBright() const
     return GetLuminance() >= 245;
 }
 
+void Color::ApplyTintOrShade(sal_Int16 n100thPercent)
+{
+    if (n100thPercent > 0)
+    {
+        basegfx::BColor aBColor = basegfx::tools::rgb2hsl(getBColor());
+
+        double fFactor = std::abs(n100thPercent) / 10000.0;
+        aBColor.setBlue(aBColor.getBlue() * fFactor + (100.0 - aBColor.getBlue()));
+        aBColor = basegfx::tools::hsl2rgb(aBColor);
+
+        SetRed(sal_uInt8((aBColor.getRed() * 255.0) + 0.5));
+        SetGreen(sal_uInt8((aBColor.getGreen() * 255.0) + 0.5));
+        SetBlue(sal_uInt8((aBColor.getBlue() * 255.0) + 0.5));
+    }
+    else if (n100thPercent < 0)
+    {
+        basegfx::BColor aBColor = basegfx::tools::rgb2hsl(getBColor());
+
+        double fFactor = std::abs(n100thPercent) / 10000.0;
+        aBColor.setBlue(aBColor.getBlue() * fFactor);
+        aBColor = basegfx::tools::hsl2rgb(aBColor);
+
+        SetRed(sal_uInt8((aBColor.getRed() * 255.0) + 0.5));
+        SetGreen(sal_uInt8((aBColor.getGreen() * 255.0) + 0.5));
+        SetBlue(sal_uInt8((aBColor.getBlue() * 255.0) + 0.5));
+    }
+}
+
 // color space conversion
 
 void Color::RGBtoHSB( sal_uInt16& nHue, sal_uInt16& nSat, sal_uInt16& nBri ) const