Applied part of #10034: wxImage::ConvertToDisabled()

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62099 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/colourcmn.cpp

@@ -149,6 +149,97 @@ wxString wxColourBase::GetAsString(long flags) const
     return colName;
 }
 
+// static
+void wxColourBase::MakeMono(unsigned char* r, unsigned char* g, unsigned char* b, 
+                            bool on)
+{
+    *r = *g = *b = on ? 255 : 0;
+}
+
+// static
+void wxColourBase::MakeGrey(unsigned char* r, unsigned char* g, unsigned char* b
+                            /*, unsigned char brightness */
+                           )
+{
+    *r = *g = *b = (wxByte)(((*b)*117UL + (*g)*601UL + (*r)*306UL) >> 10);
+}
+
+// static
+void wxColourBase::MakeGrey(unsigned char* r, unsigned char* g, unsigned char* b,
+                            double weight_r, double weight_g, double weight_b)
+{
+    double luma = (*r) * weight_r + (*g) * weight_g + (*b) * weight_b;
+    *r = *g = *b = (wxByte)wxRound(luma);
+}
+
+// static
+void wxColourBase::MakeDisabled(unsigned char* r, unsigned char* g, unsigned char* b, 
+                                unsigned char brightness)
+{
+    //MakeGrey(r, g, b, brightness); // grey no-blend version
+    *r = AlphaBlend(*r, brightness, 0.4);
+    *g = AlphaBlend(*g, brightness, 0.4);
+    *b = AlphaBlend(*b, brightness, 0.4);
+}
+
+// AlphaBlend is used by ChangeLightness and MakeDisabled
+
+// static
+unsigned char wxColourBase::AlphaBlend(unsigned char fg, unsigned char bg, 
+                                       double alpha)
+{
+    double result = bg + (alpha * (fg - bg));
+    result = wxMax(result,   0.0);
+    result = wxMin(result, 255.0);
+    return (unsigned char)result;
+}
+
+// ChangeLightness() is a utility function that simply darkens
+// or lightens a color, based on the specified percentage
+// ialpha of 0 would be completely black, 100 completely white
+// an ialpha of 100 returns the same colour
+
+// static
+void wxColourBase::ChangeLightness(unsigned char* r, unsigned char* g, unsigned char* b,
+                                   int ialpha)
+{
+    if (ialpha == 100) return;
+
+    // ialpha is 0..200 where 0 is completely black
+    // and 200 is completely white and 100 is the same
+    // convert that to normal alpha 0.0 - 1.0
+    ialpha = wxMax(ialpha,   0);
+    ialpha = wxMin(ialpha, 200);
+    double alpha = ((double)(ialpha - 100.0))/100.0;
+
+    unsigned char bg;
+    if (ialpha > 100)
+    {
+        // blend with white
+        bg = 255;
+        alpha = 1.0 - alpha;  // 0 = transparent fg; 1 = opaque fg
+    }
+    else
+    {
+        // blend with black
+        bg = 0;
+        alpha = 1.0 + alpha;  // 0 = transparent fg; 1 = opaque fg
+    }
+
+    *r = AlphaBlend(*r, bg, alpha);
+    *g = AlphaBlend(*g, bg, alpha);
+    *b = AlphaBlend(*b, bg, alpha);
+}
+
+wxColour wxColourBase::ChangeLightness(int ialpha) const
+{
+    wxByte r = Red();
+    wxByte g = Green();
+    wxByte b = Blue();
+    ChangeLightness(&r, &g, &b, ialpha);
+    return wxColour(r,g,b);
+}
+
 #if WXWIN_COMPATIBILITY_2_6
 
 // static