filter/denoising: Restore alpha after processing

As the Alpha channel is completely ignored and possibly destroyed by denoising algorithms, we should restore the Alpha channel manually. Linear interpolation was chosen here as it will behave like Point if the size matches, and properly interpolate if the size doesn't match.

Fixes: #646

source/filters/filter-denoising.cpp

@@ -97,6 +97,20 @@ denoising_instance::denoising_instance(obs_data_t* data, obs_source_t* self)
 		_input = std::make_shared<::streamfx::obs::gs::rendertarget>(GS_RGBA_UNORM, GS_ZS_NONE);
 		_input->render(1, 1); // Preallocate the RT on the driver and GPU.
 		_output = _input->get_texture();
+
+		// Load the required effect.
+		_standard_effect =
+			std::make_shared<::streamfx::obs::gs::effect>(::streamfx::data_file_path("effects/standard.effect"));
+
+		// Create Samplers
+		_channel0_sampler = std::make_shared<::streamfx::obs::gs::sampler>();
+		_channel0_sampler->set_filter(gs_sample_filter::GS_FILTER_LINEAR);
+		_channel0_sampler->set_address_mode_u(GS_ADDRESS_CLAMP);
+		_channel0_sampler->set_address_mode_v(GS_ADDRESS_CLAMP);
+		_channel1_sampler = std::make_shared<::streamfx::obs::gs::sampler>();
+		_channel1_sampler->set_filter(gs_sample_filter::GS_FILTER_LINEAR);
+		_channel1_sampler->set_address_mode_u(GS_ADDRESS_CLAMP);
+		_channel1_sampler->set_address_mode_v(GS_ADDRESS_CLAMP);
 	}
 
 	if (data) {
@@ -375,8 +389,13 @@ void denoising_instance::video_render(gs_effect_t* effect)
 #ifdef ENABLE_PROFILING
 		::streamfx::obs::gs::debug_marker profiler1{::streamfx::obs::gs::debug_color_render, "Render"};
 #endif
-		gs_effect_set_texture(gs_effect_get_param_by_name(effect, "image"), _output->get_object());
-		while (gs_effect_loop(effect, "Draw")) {
+		if (_standard_effect->has_parameter("Channel0", ::streamfx::obs::gs::effect_parameter::type::Texture)) {
+			_standard_effect->get_parameter("Channel0").set_texture(_output);
+		}
+		if (_standard_effect->has_parameter("Channel1", ::streamfx::obs::gs::effect_parameter::type::Texture)) {
+			_standard_effect->get_parameter("Channel1").set_texture(_input->get_texture());
+		}
+		while (gs_effect_loop(_standard_effect->get_object(), "RestoreAlpha")) {
 			gs_draw_sprite(nullptr, 0, _size.first, _size.second);
 		}
 	}
@@ -560,7 +579,7 @@ denoising_factory::denoising_factory()
 	// 3. In any other case, register the filter!
 	_info.id           = S_PREFIX "filter-video-denoising";
 	_info.type         = OBS_SOURCE_TYPE_FILTER;
-	_info.output_flags = OBS_SOURCE_VIDEO;
+	_info.output_flags = OBS_SOURCE_VIDEO | OBS_SOURCE_CUSTOM_DRAW;
 
 	set_resolution_enabled(true);
 	finish_setup();

source/filters/filter-denoising.hpp

@@ -22,6 +22,7 @@
 #include <atomic>
 #include <memory>
 #include <mutex>
+#include "obs/gs/gs-effect.hpp"
 #include "obs/gs/gs-rendertarget.hpp"
 #include "obs/gs/gs-texture.hpp"
 #include "obs/obs-source-factory.hpp"
@@ -52,6 +53,10 @@ namespace streamfx::filter::denoising {
 		std::mutex                              _provider_lock;
 		std::shared_ptr<util::threadpool::task> _provider_task;
 
+		std::shared_ptr<::streamfx::obs::gs::effect>  _standard_effect;
+		std::shared_ptr<::streamfx::obs::gs::sampler> _channel0_sampler;
+		std::shared_ptr<::streamfx::obs::gs::sampler> _channel1_sampler;
+
 		std::shared_ptr<::streamfx::obs::gs::rendertarget> _input;
 		std::shared_ptr<::streamfx::obs::gs::texture>      _output;
 		bool                                               _dirty;