sample-creating-texture-object.md

Code sample: Creating an OpenGL texture object from file

#include <gli/gli.hpp>

/// Filename can be KTX or DDS files
GLuint create_texture(char const* Filename)
{
	gli::texture Texture = gli::load(Filename);
	if(Texture.empty())
		return 0;

	gli::gl GL(gli::gl::PROFILE_GL33);
	gli::gl::format const Format = GL.translate(Texture.format(), Texture.swizzles());
	GLenum Target = GL.translate(Texture.target());

	GLuint TextureName = 0;
	glGenTextures(1, &TextureName);
	glBindTexture(Target, TextureName);
	glTexParameteri(Target, GL_TEXTURE_BASE_LEVEL, 0);
	glTexParameteri(Target, GL_TEXTURE_MAX_LEVEL, static_cast<GLint>(Texture.levels() - 1));
	glTexParameteri(Target, GL_TEXTURE_SWIZZLE_R, Format.Swizzles[0]);
	glTexParameteri(Target, GL_TEXTURE_SWIZZLE_G, Format.Swizzles[1]);
	glTexParameteri(Target, GL_TEXTURE_SWIZZLE_B, Format.Swizzles[2]);
	glTexParameteri(Target, GL_TEXTURE_SWIZZLE_A, Format.Swizzles[3]);

	glm::tvec3<GLsizei> const Extent(Texture.extent());
	GLsizei const FaceTotal = static_cast<GLsizei>(Texture.layers() * Texture.faces());

	switch(Texture.target())
	{
	case gli::TARGET_1D:
		glTexStorage1D(
			Target, static_cast<GLint>(Texture.levels()), Format.Internal, Extent.x);
		break;
	case gli::TARGET_1D_ARRAY:
	case gli::TARGET_2D:
	case gli::TARGET_CUBE:
		glTexStorage2D(
			Target, static_cast<GLint>(Texture.levels()), Format.Internal,
			Extent.x, Texture.target() == gli::TARGET_2D ? Extent.y : FaceTotal);
		break;
	case gli::TARGET_2D_ARRAY:
	case gli::TARGET_3D:
	case gli::TARGET_CUBE_ARRAY:
		glTexStorage3D(
			Target, static_cast<GLint>(Texture.levels()), Format.Internal,
			Extent.x, Extent.y,
			Texture.target() == gli::TARGET_3D ? Extent.z : FaceTotal);
		break;
	default:
		assert(0);
		break;
	}

	for(std::size_t Layer = 0; Layer < Texture.layers(); ++Layer)
	for(std::size_t Face = 0; Face < Texture.faces(); ++Face)
	for(std::size_t Level = 0; Level < Texture.levels(); ++Level)
	{
		GLsizei const LayerGL = static_cast<GLsizei>(Layer);
		glm::tvec3<GLsizei> Extent(Texture.extent(Level));
		Target = gli::is_target_cube(Texture.target())
			? static_cast<GLenum>(GL_TEXTURE_CUBE_MAP_POSITIVE_X + Face)
			: Target;

		switch(Texture.target())
		{
		case gli::TARGET_1D:
			if(gli::is_compressed(Texture.format()))
				glCompressedTexSubImage1D(
					Target, static_cast<GLint>(Level), 0, Extent.x,
					Format.Internal, static_cast<GLsizei>(Texture.size(Level)),
					Texture.data(Layer, Face, Level));
			else
				glTexSubImage1D(
					Target, static_cast<GLint>(Level), 0, Extent.x,
					Format.External, Format.Type,
					Texture.data(Layer, Face, Level));
			break;
		case gli::TARGET_1D_ARRAY:
		case gli::TARGET_2D:
		case gli::TARGET_CUBE:
			if(gli::is_compressed(Texture.format()))
				glCompressedTexSubImage2D(
					Target, static_cast<GLint>(Level),
					0, 0,
					Extent.x,
					Texture.target() == gli::TARGET_1D_ARRAY ? LayerGL : Extent.y,
					Format.Internal, static_cast<GLsizei>(Texture.size(Level)),
					Texture.data(Layer, Face, Level));
			else
				glTexSubImage2D(
					Target, static_cast<GLint>(Level),
					0, 0,
					Extent.x,
					Texture.target() == gli::TARGET_1D_ARRAY ? LayerGL : Extent.y,
					Format.External, Format.Type,
					Texture.data(Layer, Face, Level));
			break;
		case gli::TARGET_2D_ARRAY:
		case gli::TARGET_3D:
		case gli::TARGET_CUBE_ARRAY:
			if(gli::is_compressed(Texture.format()))
				glCompressedTexSubImage3D(
					Target, static_cast<GLint>(Level),
					0, 0, 0,
					Extent.x, Extent.y,
					Texture.target() == gli::TARGET_3D ? Extent.z : LayerGL,
					Format.Internal, static_cast<GLsizei>(Texture.size(Level)),
					Texture.data(Layer, Face, Level));
			else
				glTexSubImage3D(
					Target, static_cast<GLint>(Level),
					0, 0, 0,
					Extent.x, Extent.y,
					Texture.target() == gli::TARGET_3D ? Extent.z : LayerGL,
					Format.External, Format.Type,
					Texture.data(Layer, Face, Level));
			break;
		default: assert(0); break;
		}
	}
	return TextureName;
}