ImagePathWML: added ~SEPIA() function

src/image_modifications.cpp

@@ -200,6 +200,11 @@ surface gs_modification::operator()(const surface& src) const
 	return greyscale_image(src);
 }
 
+surface sepia_modification::operator()(const surface &src) const
+{
+	return sepia_image(src);
+}
+
 surface plot_alpha_modification::operator()(const surface& src) const
 {
 	return alpha_to_greyscale(src);
@@ -744,6 +749,12 @@ REGISTER_MOD_PARSER(GS, )
 	return new gs_modification;
 }
 
+// Sepia
+REGISTER_MOD_PARSER(SEPIA, )
+{
+	return new sepia_modification;
+}
+
 // Plot Alpha
 REGISTER_MOD_PARSER(PLOT_ALPHA, )
 {

src/image_modifications.hpp

@@ -221,6 +221,14 @@ public:
 	virtual surface operator()(const surface& src) const;
 };
 
+/**
+ * Give to the image a sepia tint (SEPIA)
+ */
+struct sepia_modification : modification
+{
+	virtual surface operator()(const surface &src) const;
+};
+
 /**
  * Plot Alpha (Alpha) modification
  */

src/sdl/utils.cpp

@@ -989,6 +989,48 @@ surface greyscale_image(const surface &surf, bool optimize)
 	return optimize ? create_optimized_surface(nsurf) : nsurf;
 }
 
+surface sepia_image(const surface &surf, bool optimize)
+{
+	if(surf == NULL)
+		return NULL;
+
+	surface nsurf(make_neutral_surface(surf));
+	if(nsurf == NULL) {
+		std::cerr << "failed to make neutral surface\n";
+		return NULL;
+	}
+
+	{
+		surface_lock lock(nsurf);
+		Uint32* beg = lock.pixels();
+		Uint32* end = beg + nsurf->w*surf->h;
+
+		while(beg != end) {
+			Uint8 alpha = (*beg) >> 24;
+
+			if(alpha) {
+				Uint8 r, g, b;
+				r = (*beg) >> 16;
+				g = (*beg) >> 8;
+				b = (*beg);
+
+				// this is the formula for applying a sepia effect
+				// that can be found on various web sites
+				// for example here: https://software.intel.com/sites/default/files/article/346220/sepiafilter-intelcilkplus.pdf
+				Uint8 outRed = std::min(255, static_cast<int>((r * 0.393) + (g * 0.769) + (b * 0.189)));
+				Uint8 outGreen = std::min(255, static_cast<int>((r * 0.349) + (g * 0.686) + (b * 0.168)));
+				Uint8 outBlue = std::min(255, static_cast<int>((r * 0.272) + (g * 0.534) + (b * 0.131)));
+
+				*beg = (alpha << 24) | (outRed << 16) | (outGreen << 8) | (outBlue);
+			}
+
+			++beg;
+		}
+	}
+
+	return optimize ? create_optimized_surface(nsurf) : nsurf;
+}
+
 surface alpha_to_greyscale(const surface &surf, bool optimize)
 {
 	if(surf == NULL)

src/sdl/utils.hpp

@@ -246,6 +246,7 @@ surface tile_surface(const surface &surf, int w, int h, bool optimize=true);
 
 surface adjust_surface_color(const surface &surf, int r, int g, int b, bool optimize=true);
 surface greyscale_image(const surface &surf, bool optimize=true);
+surface sepia_image(const surface &surf, bool optimize=true);
 surface alpha_to_greyscale(const surface & surf, bool optimize=true);
 surface wipe_alpha(const surface & surf, bool optimize=true);
 /** create an heavy shadow of the image, by blurring, increasing alpha and darkening */