Add new ~SCALE_INTO(w,h) IPF

changelog

@@ -9,6 +9,7 @@ Version 1.13.4+dev:
    * Add highlight=yes|no to [scroll_to], [scroll_to_unit], [message]
      Defaults to no in the first two cases, yes in the third
      If yes, the target hex is outlined.
+   * New ~SCALE_INTO(w,h) IPF which preserves aspect ratio, using NN.
  * Lua API:
    * wesnoth.match_unit can now take a location (rather than a unit) as
      the optional third parameter. This will cause the filter to consider

src/image_modifications.cpp

@@ -426,6 +426,41 @@ int scale_sharp_modification::get_h() const
 	return h_;
 }
 
+surface scale_into_modification::operator()(const surface& src) const
+{
+	const int old_w = src->w;
+	const int old_h = src->h;
+	long double w = w_;
+	long double h = h_;
+
+	if(w <= 0) {
+		if(w < 0) {
+			ERR_DP << "width of SCALE_INTO is negative - resetting to original width" << std::endl;
+		}
+		w = old_w;
+	}
+	if(h <= 0) {
+		if(h < 0) {
+			ERR_DP << "height of SCALE_INTO is negative - resetting to original height" << std::endl;
+		}
+		h = old_h;
+	}
+
+	long double ratio = std::min(w / old_w, h / old_h);
+
+	return scale_surface_sharp(src, old_w * ratio, old_h * ratio);
+}
+
+int scale_into_modification::get_w() const
+{
+	return w_;
+}
+
+int scale_into_modification::get_h() const
+{
+	return h_;
+}
+
 surface xbrz_modification::operator()(const surface& src) const
 {
 	if (z_ == 1) {
@@ -1080,6 +1115,27 @@ REGISTER_MOD_PARSER(SCALE_SHARP, args)
 	return new scale_sharp_modification(w, h);
 }
 
+REGISTER_MOD_PARSER(SCALE_INTO, args)
+{
+	std::vector<std::string> const& scale_params = utils::split(args, ',', utils::STRIP_SPACES);
+	const size_t s = scale_params.size();
+
+	if(s == 0 || (s == 1 && scale_params[0].empty())) {
+		ERR_DP << "no arguments passed to the ~SCALE_INTO() function" << std::endl;
+		return NULL;
+	}
+
+	int w = 0, h = 0;
+
+	w = lexical_cast_default<int, const std::string&>(scale_params[0]);
+
+	if(s > 1) {
+		h = lexical_cast_default<int, const std::string&>(scale_params[1]);
+	}
+
+	return new scale_into_modification(w, h);
+}
+
 
 // xBRZ
 REGISTER_MOD_PARSER(XBRZ, args)

src/image_modifications.hpp

@@ -401,6 +401,24 @@ class scale_sharp_modification : public modification
 	int w_, h_;
 };
 
+/**
+ * Scale into (SCALE_INTO) modification. (Uses nearest neighbor.)
+ * Preserves aspect ratio.
+ */
+class scale_into_modification : public modification
+{
+public:
+	scale_into_modification(int width, int height)
+		: w_(width), h_(height)
+	{}
+	virtual surface operator()(const surface& src) const;
+	int get_w() const;
+	int get_h() const;
+
+private:
+	int w_, h_;
+};
+
 
 /**
  * xBRZ scale (xBRZ) modification