Add simple gamma correction effect

libs/gfx/include/psemek/gfx/effect/gamma.hpp

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <psemek/gfx/texture.hpp>
+#include <psemek/gfx/render_target.hpp>
+
+#include <psemek/util/pimpl.hpp>
+
+namespace psemek::gfx
+{
+
+	struct gamma_correction
+	{
+		gamma_correction();
+		~gamma_correction();
+
+		struct options
+		{
+			float gamma = 1.f / 2.2f;
+		};
+
+		void invoke(texture_2d const & src, render_target const & dst, options const & opts);
+
+	private:
+		psemek_declare_pimpl
+	};
+
+}

libs/gfx/source/effect/gamma.cpp

@@ -0,0 +1,80 @@
+#include <psemek/gfx/effect/gamma.hpp>
+#include <psemek/gfx/program.hpp>
+#include <psemek/gfx/array.hpp>
+#include <psemek/gfx/error.hpp>
+
+namespace psemek::gfx
+{
+
+	static char const gamma_vs[] =
+R"(#version 330
+
+const vec4 vertices[6] = vec4[6](
+	vec4(-1.0, -1.0, 0.0, 1.0),
+	vec4( 1.0, -1.0, 0.0, 1.0),
+	vec4( 1.0,  1.0, 0.0, 1.0),
+
+	vec4(-1.0, -1.0, 0.0, 1.0),
+	vec4( 1.0,  1.0, 0.0, 1.0),
+	vec4(-1.0,  1.0, 0.0, 1.0)
+);
+
+out vec2 texcoord;
+
+void main()
+{
+	gl_Position = vertices[gl_VertexID];
+
+	texcoord = vertices[gl_VertexID].xy * 0.5 + vec2(0.5);
+}
+)";
+
+	static char const gamma_fs[] =
+R"(#version 330
+
+uniform float u_gamma;
+uniform sampler2D u_input;
+
+in vec2 texcoord;
+
+out vec4 out_color;
+
+void main()
+{
+	vec4 color = texture(u_input, texcoord);
+	color.rgb = pow(color.rgb, vec3(u_gamma));
+	out_color = color;
+}
+)";
+
+	struct gamma_correction::impl
+	{
+		gfx::program program{gamma_vs, gamma_fs};
+		gfx::array array;
+	};
+
+	gamma_correction::gamma_correction()
+		: pimpl_{std::make_unique<struct impl>()}
+	{
+		impl().program.bind();
+		impl().program["u_input"] = 0;
+	}
+
+	gamma_correction::~gamma_correction() = default;
+
+	void gamma_correction::invoke(texture_2d const & src, render_target const & dst, options const & opts)
+	{
+		gl::Disable(gl::BLEND);
+		gl::Disable(gl::DEPTH_TEST);
+		gl::Disable(gl::CULL_FACE);
+
+		dst.bind();
+		gl::ActiveTexture(gl::TEXTURE0);
+		src.bind();
+		impl().array.bind();
+		impl().program.bind();
+		impl().program["u_gamma"] = opts.gamma;
+		gl::DrawArrays(gl::TRIANGLES, 0, 6);
+	}
+
+}