Lua (d)bitmap: add hflip and vflip functions

include/lua/bitmap.hpp

@@ -56,6 +56,8 @@ struct lua_bitmap
 	int pset(lua::state& L, lua::parameters& P);
 	int pget(lua::state& L, lua::parameters& P);
 	int size(lua::state& L, lua::parameters& P);
+	int hflip(lua::state& L, lua::parameters& P);
+	int vflip(lua::state& L, lua::parameters& P);
 	int hash(lua::state& L, lua::parameters& P);
 	template<bool scaled, bool porterduff> int blit(lua::state& L, lua::parameters& P);
 	template<bool scaled> int blit_priority(lua::state& L, lua::parameters& P);
@@ -81,6 +83,8 @@ struct lua_dbitmap
 	int pset(lua::state& L, lua::parameters& P);
 	int pget(lua::state& L, lua::parameters& P);
 	int size(lua::state& L, lua::parameters& P);
+	int hflip(lua::state& L, lua::parameters& P);
+	int vflip(lua::state& L, lua::parameters& P);
 	int hash(lua::state& L, lua::parameters& P);
 	template<bool scaled, bool porterduff> int blit(lua::state& L, lua::parameters& P);
 	int save_png(lua::state& L, lua::parameters& P);

lua.lyx

@@ -2422,6 +2422,30 @@ Samples the source as texture, performing linear transform (with nearest-neighbo
 r sampling) and writes the result to this bitmap.
 \end_layout
 
+\begin_layout Subsubsection
+Method hflip: Horizontally flip a bitmap
+\end_layout
+
+\begin_layout Itemize
+Syntax: none bitmap:hflip()
+\end_layout
+
+\begin_layout Standard
+Horizontally flips a bitmap.
+\end_layout
+
+\begin_layout Subsubsection
+Method vflip: Vertically flip a bitmap
+\end_layout
+
+\begin_layout Itemize
+Syntax: none bitmap:vflip()
+\end_layout
+
+\begin_layout Standard
+Vertically flips a bitmap.
+\end_layout
+
 \begin_layout Standard
 \begin_inset Newpage pagebreak
 \end_inset
@@ -3196,6 +3220,33 @@ wrap: boolean: If true, wrap the texture.
 \begin_layout Standard
 Samples the source as texture, performing linear transform (with nearest-neighbo
 r sampling) and writes the result to this bitmap.
+\end_layout
+
+\begin_layout Subsubsection
+Method hflip: Horizontally flip a bitmap
+\end_layout
+
+\begin_layout Itemize
+Syntax: none dbitmap:hflip()
+\end_layout
+
+\begin_layout Standard
+Horizontally flips a bitmap.
+\end_layout
+
+\begin_layout Subsubsection
+Method vflip: Vertically flip a bitmap
+\end_layout
+
+\begin_layout Itemize
+Syntax: none dbitmap:vflip()
+\end_layout
+
+\begin_layout Standard
+Vertically flips a bitmap.
+\end_layout
+
+\begin_layout Standard
 \begin_inset Newpage pagebreak
 \end_inset
 

src/lua/gui-bitmap.cpp

@@ -634,6 +634,33 @@ namespace
 		}
 	}
 
+	template<typename pixel>
+	inline int _hflip(pixel* pixels, uint32_t width, uint32_t height)
+	{
+		uint32_t w = width, h = height;
+
+		for (uint32_t x = 0; x < w/2; x++) {
+			for (uint32_t y = 0; y < h; y++) {
+				std::swap(pixels[y * w + x], pixels[(y + 1) * w - x - 1]);
+			}
+		}
+		return 0;
+	}
+
+	template<typename pixel>
+	inline int _vflip(pixel* pixels, uint32_t width, uint32_t height)
+	{
+		uint32_t w = width, h = height;
+
+		for (uint32_t x = 0; x < w; x++) {
+			for (uint32_t y = 0; y < h/2; y++) {
+				std::swap(pixels[y * w + x], pixels[(h - y - 1) * w + x]);
+			}
+		}
+		return 0;
+	}
+
+
 	inline int64_t mangle_color(uint32_t c)
 	{
 		if(c < 0x1000000)
@@ -829,6 +856,8 @@ namespace
 		{"pset", &lua_bitmap::pset},
 		{"pget", &lua_bitmap::pget},
 		{"size", &lua_bitmap::size},
+		{"hflip", &lua_bitmap::hflip},
+		{"vflip", &lua_bitmap::vflip},
 		{"hash", &lua_bitmap::hash},
 		{"blit", &lua_bitmap::blit<false, false>},
 		{"blit_priority", &lua_bitmap::blit_priority<false>},
@@ -850,6 +879,8 @@ namespace
 		{"pset", &lua_dbitmap::pset},
 		{"pget", &lua_dbitmap::pget},
 		{"size", &lua_dbitmap::size},
+		{"hflip", &lua_dbitmap::hflip},
+		{"vflip", &lua_dbitmap::vflip},
 		{"hash", &lua_dbitmap::hash},
 		{"blit", &lua_dbitmap::blit<false, false>},
 		{"blit_scaled", &lua_dbitmap::blit<true, false>},
@@ -1102,6 +1133,16 @@ int lua_bitmap::size(lua::state& L, lua::parameters& P)
 	return 2;
 }
 
+int lua_bitmap::hflip(lua::state& L, lua::parameters& P)
+{
+	return _hflip(pixels, width, height);
+}
+
+int lua_bitmap::vflip(lua::state& L, lua::parameters& P)
+{
+	return _vflip(pixels, width, height);
+}
+
 int lua_bitmap::hash(lua::state& L, lua::parameters& P)
 {
 	sha256 h;
@@ -1289,6 +1330,16 @@ int lua_dbitmap::size(lua::state& L, lua::parameters& P)
 	return 2;
 }
 
+int lua_dbitmap::hflip(lua::state& L, lua::parameters& P)
+{
+	return _hflip(pixels, width, height);
+}
+
+int lua_dbitmap::vflip(lua::state& L, lua::parameters& P)
+{
+	return _vflip(pixels, width, height);
+}
+
 int lua_dbitmap::hash(lua::state& L, lua::parameters& P)
 {
 	sha256 h;