added global parameters to image loader that allow addition of file format specific paramters. Here:

normalmap paramter for ktx2 and uastc srgb parameter for forced uastc export

Author: kopaka1822

DxImageLoader/interface.cpp

@@ -22,6 +22,7 @@ static uint32_t s_last_progress = -1;
 
 // key = extension (e.g. png), value = DXGI formats
 static std::map<std::string, std::vector<uint32_t>> s_exportFormats;
+static std::map<std::string, int> s_globalParameteri;
 
 bool hasEnding(std::string const& fullString, std::string const& ending) {
 	if (fullString.length() >= ending.length()) {
@@ -302,6 +303,39 @@ const uint32_t* get_export_formats(const char* extension, int& numFormats)
 	return it->second.data();
 }
 
+bool get_global_parameter_i(const char* name, int& results)
+{
+	if (s_globalParameteri.empty())
+	{
+		// insert default values
+		set_global_parameter_i("normalmap", 0);
+		set_global_parameter_i("uastc srgb", 0);
+	}
+
+	auto it = s_globalParameteri.find(name);
+	if (it == s_globalParameteri.end())
+	{
+	    set_error("could not find global parameter: " + std::string(name));
+		return false;
+	}
+
+	results = it->second;
+	return true;
+}
+
+int get_global_parameter_i(const char* name)
+{
+	int res = 0;
+	if(get_global_parameter_i(name, res)) return res;
+
+	throw std::runtime_error(s_error);
+}
+
+void set_global_parameter_i(const char* name, int value)
+{
+	s_globalParameteri[name] = value;
+}
+
 void set_progress_callback(ProgressCallback cb)
 {
 	s_progress_callback = cb;

DxImageLoader/interface.h

@@ -47,6 +47,19 @@ EXPORT(bool) image_save(int id, const char* filename, const char* extension, uin
 /// \brief retrieves an array with all supported dxgi formats that are available for export with the extension
 EXPORT(const uint32_t*) get_export_formats(const char* extension, int& numFormats);
 
+/// List of global parameters:
+/// "uastc srgb" - for .ktx2 export => use uastc for srgb compression (otherwise etc1 is used). Valid for srgb uastc compressable textures
+/// "normalmap" - for .ktx2 export => indicate that the exporter/compressor should optimize data for normal maps. Valid for linear (non-srgb) uastc compressable textures
+
+/// \brief stores the value of the parameter in the results argument and returns true if found. Returns false otherwise
+EXPORT(bool)  get_global_parameter_i(const char* name, int& results);
+
+/// \brief returns the value of the parameter if found. Throws an exception otherwise
+int get_global_parameter_i(const char* name);
+
+/// \brief sets the value of a global parameter or 0 if not found
+EXPORT(void) set_global_parameter_i(const char* name, int value);
+
 typedef uint32_t(__stdcall* ProgressCallback)(float, const char*);
 
 /// \brief sets the progress report callback

DxImageLoader/ktx_interface.cpp

@@ -85,14 +85,17 @@ void ktx2_save_image(const char* filename, GliImage& image, gli::format format,
 		params.threadCount = std::thread::hardware_concurrency();
 		params.compressionLevel = KTX_ETC1S_DEFAULT_COMPRESSION_LEVEL;
 		params.qualityLevel = std::max((quality * 254) / 99 + 1, 1); // scale quality [0, 99] between [1, 255]
-		// params.normalMap // TODO add this later?
+		params.normalMap = KTX_FALSE;
+		if (!gli::is_srgb(format)) // only valid for linear textures
+	        params.normalMap = get_global_parameter_i("normalmap") ? KTX_TRUE : KTX_FALSE;
 
 	    // select uastc for everything that is not color (here: for everyhing that is not SRGB)
-		if(!gli::is_srgb(format))
+		// unless the "uastc srgb" flag is set => then use usastc as well
+		if(!gli::is_srgb(format) || get_global_parameter_i("uastc srgb"))
 		{
 		    params.uastc = KTX_TRUE;
 			params.uastcFlags = KTX_PACK_UASTC_MAX_LEVEL; // maximum supported quality
-			params.uastcRDO = KTX_TRUE; // Enable Rate Distortion Optimization (RDO) post-processing.
+			params.uastcRDO = params.normalMap ? KTX_FALSE : KTX_TRUE;
 		}
 
 		// optional if compression