ipa: rkisp1: awb: Add support for RGB means

RkISP actually supports two modes for color means, RGB and YCbCr. The
variables where the means are stored are identically named regardless of
the color means mode that's been selected.

Since the gains are computed in RGB mode, a conversion needs to be done
when the mode is YCbCr, which is unnecessary when RGB mode is selected.

This adds support for RGB means mode too, by checking at runtime which
mode is selected at a given time. The default is still set to YCbCr mode
for now.

Cc: Quentin Schulz <foss+libcamera@0leil.net>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

2 files changed, 88 insertions, 50 deletions

diff --git a/src/ipa/rkisp1/algorithms/awb.cpp b/src/ipa/rkisp1/algorithms/awb.cpp
index 694d97cc..cde5b981 100644
--- a/src/ipa/rkisp1/algorithms/awb.cpp
+++ b/src/ipa/rkisp1/algorithms/awb.cpp
@@ -30,6 +30,11 @@ namespace ipa::rkisp1::algorithms {
 
 LOG_DEFINE_CATEGORY(RkISP1Awb)
 
+Awb::Awb()
+	: rgbMode_(false)
+{
+}
+
 /**
  * \copydoc libcamera::ipa::Algorithm::configure
  */
@@ -98,38 +103,60 @@ void Awb::prepare(IPAContext &context, const uint32_t frame,
 	/* Update the gains. */
 	params->module_cfg_update |= RKISP1_CIF_ISP_MODULE_AWB_GAIN;
 
-	/* If we already have configured the gains and window, return. */
+	/* If we have already set the AWB measurement parameters, return. */
 	if (frame > 0)
 		return;
 
-	/* Configure the gains to apply. */
+	rkisp1_cif_isp_awb_meas_config &awb_config = params->meas.awb_meas_config;
+
+	/* Configure the measure window for AWB. */
+	awb_config.awb_wnd = context.configuration.awb.measureWindow;
+
+	/* Number of frames to use to estimate the means (0 means 1 frame). */
+	awb_config.frames = 0;
+
+	/* Select RGB or YCbCr means measurement. */
+	if (rgbMode_) {
+		awb_config.awb_mode = RKISP1_CIF_ISP_AWB_MODE_RGB;
+
+		/*
+		 * For RGB-based measurements, pixels are selected with maximum
+		 * red, green and blue thresholds that are set in the
+		 * awb_ref_cr, awb_min_y and awb_ref_cb respectively. The other
+		 * values are not used, set them to 0.
+		 */
+		awb_config.awb_ref_cr = 250;
+		awb_config.min_y = 250;
+		awb_config.awb_ref_cb = 250;
+
+		awb_config.max_y = 0;
+		awb_config.min_c = 0;
+		awb_config.max_csum = 0;
+	} else {
+		awb_config.awb_mode = RKISP1_CIF_ISP_AWB_MODE_YCBCR;
+
+		/* Set the reference Cr and Cb (AWB target) to white. */
+		awb_config.awb_ref_cb = 128;
+		awb_config.awb_ref_cr = 128;
+
+		/*
+		 * Filter out pixels based on luminance and chrominance values.
+		 * The acceptable luma values are specified as a [16, 250]
+		 * range, while the acceptable chroma values are specified with
+		 * a minimum of 16 and a maximum Cb+Cr sum of 250.
+		 */
+		awb_config.min_y = 16;
+		awb_config.max_y = 250;
+		awb_config.min_c = 16;
+		awb_config.max_csum = 250;
+	}
+
+	/* Enable the AWB gains. */
 	params->module_en_update |= RKISP1_CIF_ISP_MODULE_AWB_GAIN;
-	/* Update the ISP to apply the gains configured. */
 	params->module_ens |= RKISP1_CIF_ISP_MODULE_AWB_GAIN;
 
-	/* Configure the measure window for AWB. */
-	params->meas.awb_meas_config.awb_wnd = context.configuration.awb.measureWindow;
-	/*
-	 * Measure Y, Cr and Cb means.
-	 * \todo RGB is not working, the kernel seems to not configure it ?
-	 */
-	params->meas.awb_meas_config.awb_mode = RKISP1_CIF_ISP_AWB_MODE_YCBCR;
-	/* Reference Cr and Cb. */
-	params->meas.awb_meas_config.awb_ref_cb = 128;
-	params->meas.awb_meas_config.awb_ref_cr = 128;
-	/* Y values to include are between min_y and max_y only. */
-	params->meas.awb_meas_config.min_y = 16;
-	params->meas.awb_meas_config.max_y = 250;
-	/* Maximum Cr+Cb value to take into account for awb. */
-	params->meas.awb_meas_config.max_csum = 250;
-	/* Minimum Cr and Cb values to take into account. */
-	params->meas.awb_meas_config.min_c = 16;
-	/* Number of frames to use to estimate the mean (0 means 1 frame). */
-	params->meas.awb_meas_config.frames = 0;
-
-	/* Update AWB measurement unit configuration. */
+	/* Update the AWB measurement parameters and enable the AWB module. */
 	params->module_cfg_update |= RKISP1_CIF_ISP_MODULE_AWB;
-	/* Make sure the ISP is measuring the means for the next frame. */
 	params->module_en_update |= RKISP1_CIF_ISP_MODULE_AWB;
 	params->module_ens |= RKISP1_CIF_ISP_MODULE_AWB;
 }
@@ -182,30 +209,39 @@ void Awb::process(IPAContext &context,
 	const rkisp1_cif_isp_stat *params = &stats->params;
 	const rkisp1_cif_isp_awb_stat *awb = &params->awb;
 	IPAActiveState &activeState = context.activeState;
-
-	/* Get the YCbCr mean values */
-	double yMean = awb->awb_mean[0].mean_y_or_g;
-	double crMean = awb->awb_mean[0].mean_cr_or_r;
-	double cbMean = awb->awb_mean[0].mean_cb_or_b;
-
-	/*
-	 * Convert from YCbCr to RGB.
-	 * The hardware uses the following formulas:
-	 * Y = 16 + 0.2500 R + 0.5000 G + 0.1094 B
-	 * Cb = 128 - 0.1406 R - 0.2969 G + 0.4375 B
-	 * Cr = 128 + 0.4375 R - 0.3750 G - 0.0625 B
-	 *
-	 * The inverse matrix is thus:
-	 * [[1,1636, -0,0623,  1,6008]
-	 *  [1,1636, -0,4045, -0,7949]
-	 *  [1,1636,  1,9912, -0,0250]]
-	 */
-	yMean -= 16;
-	cbMean -= 128;
-	crMean -= 128;
-	double redMean = 1.1636 * yMean - 0.0623 * cbMean + 1.6008 * crMean;
-	double greenMean = 1.1636 * yMean - 0.4045 * cbMean - 0.7949 * crMean;
-	double blueMean = 1.1636 * yMean + 1.9912 * cbMean - 0.0250 * crMean;
+	double greenMean;
+	double redMean;
+	double blueMean;
+
+	if (rgbMode_) {
+		greenMean = awb->awb_mean[0].mean_y_or_g;
+		redMean = awb->awb_mean[0].mean_cr_or_r;
+		blueMean = 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;
+
+		/*
+		 * Convert from YCbCr to RGB.
+		 * The hardware uses the following formulas:
+		 * Y = 16 + 0.2500 R + 0.5000 G + 0.1094 B
+		 * Cb = 128 - 0.1406 R - 0.2969 G + 0.4375 B
+		 * Cr = 128 + 0.4375 R - 0.3750 G - 0.0625 B
+		 *
+		 * The inverse matrix is thus:
+		 * [[1,1636, -0,0623,  1,6008]
+		 *  [1,1636, -0,4045, -0,7949]
+		 *  [1,1636,  1,9912, -0,0250]]
+		 */
+		yMean -= 16;
+		cbMean -= 128;
+		crMean -= 128;
+		redMean = 1.1636 * yMean - 0.0623 * cbMean + 1.6008 * crMean;
+		greenMean = 1.1636 * yMean - 0.4045 * cbMean - 0.7949 * crMean;
+		blueMean = 1.1636 * yMean + 1.9912 * cbMean - 0.0250 * crMean;
+	}
 
 	/*
 	 * The ISP computes the AWB means after applying the colour gains,
diff --git a/src/ipa/rkisp1/algorithms/awb.h b/src/ipa/rkisp1/algorithms/awb.h
index 6d4a3946..d76b5382 100644
--- a/src/ipa/rkisp1/algorithms/awb.h
+++ b/src/ipa/rkisp1/algorithms/awb.h
@@ -16,7 +16,7 @@ namespace ipa::rkisp1::algorithms {
 class Awb : public Algorithm
 {
 public:
-	Awb() = default;
+	Awb();
 	~Awb() = default;
 
 	int configure(IPAContext &context, const IPACameraSensorInfo &configInfo) override;
@@ -32,6 +32,8 @@ public:
 
 private:
 	uint32_t estimateCCT(double red, double green, double blue);
+
+	bool rgbMode_;
 };
 
 } /* namespace ipa::rkisp1::algorithms */