Method generate_mipmaps

framework/scene_graph/components/image.cpp:262–310

}

void Image::generate_mipmaps()
{
	assert(mipmaps.size() == 1 && "Mipmaps already generated");

	if (mipmaps.size() > 1)
	{
		return;        // Do not generate again
	}

	auto extent      = get_extent();
	auto next_width  = std::max<uint32_t>(1u, extent.width / 2);
	auto next_height = std::max<uint32_t>(1u, extent.height / 2);
	auto channels    = 4;
	auto next_size   = next_width * next_height * channels;

	// Allocate for all the mips at once.  The function returns the total size needed for the
	// existing base mip as well as all the mips that will be generated.
	data.reserve(get_required_mipmaps_size(extent));

	while (true)
	{
		// Make space for next mipmap
		auto old_size = to_u32(data.size());
		data.resize(old_size + next_size);

		auto &prev_mipmap = mipmaps.back();
		// Update mipmaps
		Mipmap next_mipmap{};
		next_mipmap.level  = prev_mipmap.level + 1;
		next_mipmap.offset = old_size;
		next_mipmap.extent = {next_width, next_height, 1u};

		// Fill next mipmap memory
		stbir_resize_uint8(data.data() + prev_mipmap.offset, prev_mipmap.extent.width, prev_mipmap.extent.height, 0,
		                   data.data() + next_mipmap.offset, next_mipmap.extent.width, next_mipmap.extent.height, 0, channels);

		mipmaps.emplace_back(std::move(next_mipmap));

		// Next mipmap values
		next_width  = std::max<uint32_t>(1u, next_width / 2);
		next_height = std::max<uint32_t>(1u, next_height / 2);
		next_size   = next_width * next_height * channels;

		if (next_width == 1 && next_height == 1)
		{
			break;
		}
	}
}

std::vector<Mipmap> &Image::get_mut_mipmaps()
{