[RFC,v2,12/12] ipa: rkisp1: awb: Replace manual calculations with Vector and Matrix

21954 diff mbox series

Processing of the statistics and estimation of the colour temperature
involve linear algebra. Replace the manual calculations with usage of
the Vector and Matrix classes.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
Changes since v1:

- Adapt to Vector::normalize() being dropped
---
 src/ipa/rkisp1/algorithms/awb.cpp | 44 +++++++++++++++++++------------
 1 file changed, 27 insertions(+), 17 deletions(-)

Laurent Pinchart <laurent.pinchart@ideasonboard.com> writes:

> Processing of the statistics and estimation of the colour temperature
> involve linear algebra. Replace the manual calculations with usage of
> the Vector and Matrix classes.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Reviewed-by: Milan Zamazal <mzamazal@redhat.com>

> ---
> Changes since v1:
>
> - Adapt to Vector::normalize() being dropped
> ---
>  src/ipa/rkisp1/algorithms/awb.cpp | 44 +++++++++++++++++++------------
>  1 file changed, 27 insertions(+), 17 deletions(-)
>
> diff --git a/src/ipa/rkisp1/algorithms/awb.cpp b/src/ipa/rkisp1/algorithms/awb.cpp
> index 1c572055acdd..97163e0fa45c 100644
> --- a/src/ipa/rkisp1/algorithms/awb.cpp
> +++ b/src/ipa/rkisp1/algorithms/awb.cpp
> @@ -169,17 +169,21 @@ void Awb::prepare(IPAContext &context, const uint32_t frame,
>  
>  uint32_t Awb::estimateCCT(const RGB<double> &rgb)
>  {
> -	/* Convert the RGB values to CIE tristimulus values (XYZ) */
> -	double X = -0.14282 * rgb.r() + 1.54924 * rgb.g() - 0.95641 * rgb.b();
> -	double Y = -0.32466 * rgb.r() + 1.57837 * rgb.g() - 0.73191 * rgb.b();
> -	double Z = -0.68202 * rgb.r() + 0.77073 * rgb.g() + 0.56332 * rgb.b();
> +	/*
> +	 * Convert the RGB values to CIE tristimulus values (XYZ) and divide by
> +	 * the sum of X, Y and Z to calculate the CIE xy chromaticity.
> +	 */
> +	static const Matrix<double, 3, 3> rgb2xyz({
> +		-0.14282, 1.54924, -0.95641,
> +		-0.32466, 1.57837, -0.73191,
> +		-0.68202, 0.77073,  0.56332
> +	});
>  
> -	/* Calculate the normalized chromaticity values */
> -	double x = X / (X + Y + Z);
> -	double y = Y / (X + Y + Z);
> +	Vector<double, 3> xyz = rgb2xyz * rgb;
> +	xyz /= xyz.sum();
>  
>  	/* Calculate CCT */
> -	double n = (x - 0.3320) / (0.1858 - y);
> +	double n = (xyz.x() - 0.3320) / (0.1858 - xyz.y());
>  	return 449 * n * n * n + 3525 * n * n + 6823.3 * n + 5520.33;
>  }
>  
> @@ -215,9 +219,11 @@ void Awb::process(IPAContext &context,
>  		rgbMeans.b() = awb->awb_mean[0].mean_cb_or_b;
>  	} else {
>  		/* Get the YCbCr mean values */
> -		double yMean = awb->awb_mean[0].mean_y_or_g;
> -		double cbMean = awb->awb_mean[0].mean_cb_or_b;
> -		double crMean = awb->awb_mean[0].mean_cr_or_r;
> +		Vector<double, 3> yuvMeans({
> +			static_cast<double>(awb->awb_mean[0].mean_y_or_g),
> +			static_cast<double>(awb->awb_mean[0].mean_cb_or_b),
> +			static_cast<double>(awb->awb_mean[0].mean_cr_or_r)
> +		});
>  
>  		/*
>  		 * Convert from YCbCr to RGB.
> @@ -231,12 +237,16 @@ void Awb::process(IPAContext &context,
>  		 *  [1,1636, -0,4045, -0,7949]
>  		 *  [1,1636,  1,9912, -0,0250]]
>  		 */
> -		yMean -= 16;
> -		cbMean -= 128;
> -		crMean -= 128;
> -		rgbMeans.r() = 1.1636 * yMean - 0.0623 * cbMean + 1.6008 * crMean;
> -		rgbMeans.g() = 1.1636 * yMean - 0.4045 * cbMean - 0.7949 * crMean;
> -		rgbMeans.b() = 1.1636 * yMean + 1.9912 * cbMean - 0.0250 * crMean;
> +		static const Matrix<double, 3, 3> yuv2rgbMatrix({
> +			1.1636, -0.0623,  1.6008,
> +			1.1636, -0.4045, -0.7949,
> +			1.1636,  1.9912, -0.0250
> +		});
> +		static const Vector<double, 3> yuv2rgbOffset({
> +			16, 128, 128
> +		});
> +
> +		rgbMeans = yuv2rgbMatrix * (yuvMeans - yuv2rgbOffset);
>  
>  		/*
>  		 * Due to hardware rounding errors in the YCbCr means, the