Function image_preprocess_normalize

Source/astcenccli_toplevel.cpp:1418–1452

* @brief Create a copy of @c input with forced unit-length normal vectors. * * It is assumed that all normal vectors are stored in the RGB components, and * stored in a packed unsigned range of [0,1] which must be unpacked prior * normalization. Data must then be repacked into this form for handing over to * the core codec. * * @param[in] input The input image. * @param[out] output T

 * @param[out] output   The output image, must use F32 components.
 */
static void image_preprocess_normalize(
	const astcenc_image& input,
	astcenc_image& output
) {
	for (unsigned int z = 0; z < input.dim_z; z++)
	{
		for (unsigned int y = 0; y < input.dim_y; y++)
		{
			for (unsigned int x = 0; x < input.dim_x; x++)
			{
				vfloat4 pixel = image_get_pixel(input, x, y, z);

				// Stash alpha component and zero
				float a = pixel.lane<3>();
				pixel.set_lane<3>(0.0f);

				// Decode [0,1] normals to [-1,1]
				pixel.set_lane<0>((pixel.lane<0>() * 2.0f) - 1.0f);
				pixel.set_lane<1>((pixel.lane<1>() * 2.0f) - 1.0f);
				pixel.set_lane<2>((pixel.lane<2>() * 2.0f) - 1.0f);

				// Normalize pixel and restore alpha
				pixel = normalize(pixel);
				pixel.set_lane<3>(a);

				// Encode [-1,1] normals to [0,1]
				pixel.set_lane<0>((pixel.lane<0>() + 1.0f) / 2.0f);
				pixel.set_lane<1>((pixel.lane<1>() + 1.0f) / 2.0f);
				pixel.set_lane<2>((pixel.lane<2>() + 1.0f) / 2.0f);

				image_set_pixel(output, x, y, z, pixel);
			}
		}
	}
}

/**
 * @brief Linearize an sRGB value.