ipa: rkisp1: Introduce AWB
The RkISP1 ISP calculates a mean value for Y, Cr and Cb at each frame. There is a RGB mode which could theoretically give us the values for R, G and B directly, but it seems to be failing right now. Convert those values into R, G and B and estimate the gain to apply in a grey world. Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com> Tested-by: Peter Griffin <peter.griffin@linaro.org> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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Jean-Michel Hautbois
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src/ipa/rkisp1/algorithms/awb.cpp
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178
src/ipa/rkisp1/algorithms/awb.cpp
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
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/*
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* Copyright (C) 2021-2022, Ideas On Board
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*
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* awb.cpp - AWB control algorithm
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*/
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#include "awb.h"
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#include <algorithm>
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#include <cmath>
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#include <libcamera/base/log.h>
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#include <libcamera/ipa/core_ipa_interface.h>
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/**
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* \file awb.h
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*/
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namespace libcamera {
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namespace ipa::rkisp1::algorithms {
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/**
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* \class Awb
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* \brief A Grey world white balance correction algorithm
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*/
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LOG_DEFINE_CATEGORY(RkISP1Awb)
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/**
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* \copydoc libcamera::ipa::Algorithm::configure
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*/
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int Awb::configure(IPAContext &context,
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const IPACameraSensorInfo &configInfo)
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{
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context.frameContext.awb.gains.red = 1.0;
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context.frameContext.awb.gains.blue = 1.0;
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context.frameContext.awb.gains.green = 1.0;
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/*
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* Define the measurement window for AWB as a centered rectangle
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* covering 3/4 of the image width and height.
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*/
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context.configuration.awb.measureWindow.h_offs = configInfo.outputSize.width / 8;
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context.configuration.awb.measureWindow.v_offs = configInfo.outputSize.height / 8;
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context.configuration.awb.measureWindow.h_size = 3 * configInfo.outputSize.width / 4;
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context.configuration.awb.measureWindow.v_size = 3 * configInfo.outputSize.height / 4;
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return 0;
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}
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uint32_t Awb::estimateCCT(double red, double green, double blue)
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{
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/* Convert the RGB values to CIE tristimulus values (XYZ) */
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double X = (-0.14282) * (red) + (1.54924) * (green) + (-0.95641) * (blue);
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double Y = (-0.32466) * (red) + (1.57837) * (green) + (-0.73191) * (blue);
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double Z = (-0.68202) * (red) + (0.77073) * (green) + (0.56332) * (blue);
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/* Calculate the normalized chromaticity values */
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double x = X / (X + Y + Z);
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double y = Y / (X + Y + Z);
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/* Calculate CCT */
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double n = (x - 0.3320) / (0.1858 - y);
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return 449 * n * n * n + 3525 * n * n + 6823.3 * n + 5520.33;
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}
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/**
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* \copydoc libcamera::ipa::Algorithm::prepare
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*/
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void Awb::prepare(IPAContext &context, rkisp1_params_cfg *params)
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{
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params->others.awb_gain_config.gain_green_b = 256 * context.frameContext.awb.gains.green;
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params->others.awb_gain_config.gain_blue = 256 * context.frameContext.awb.gains.blue;
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params->others.awb_gain_config.gain_red = 256 * context.frameContext.awb.gains.red;
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params->others.awb_gain_config.gain_green_r = 256 * context.frameContext.awb.gains.green;
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/* Update the gains. */
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params->module_cfg_update |= RKISP1_CIF_ISP_MODULE_AWB_GAIN;
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/* If we already have configured the gains and window, return. */
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if (context.frameContext.frameCount > 0)
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return;
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/* Configure the gains to apply. */
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params->module_en_update |= RKISP1_CIF_ISP_MODULE_AWB_GAIN;
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/* Update the ISP to apply the gains configured. */
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params->module_ens |= RKISP1_CIF_ISP_MODULE_AWB_GAIN;
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/* Configure the measure window for AWB. */
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params->meas.awb_meas_config.awb_wnd = context.configuration.awb.measureWindow;
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/*
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* Measure Y, Cr and Cb means.
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* \todo RGB is not working, the kernel seems to not configure it ?
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*/
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params->meas.awb_meas_config.awb_mode = RKISP1_CIF_ISP_AWB_MODE_YCBCR;
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/* Reference Cr and Cb. */
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params->meas.awb_meas_config.awb_ref_cb = 128;
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params->meas.awb_meas_config.awb_ref_cr = 128;
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/* Y values to include are between min_y and max_y only. */
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params->meas.awb_meas_config.min_y = 16;
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params->meas.awb_meas_config.max_y = 250;
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/* Maximum Cr+Cb value to take into account for awb. */
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params->meas.awb_meas_config.max_csum = 250;
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/* Minimum Cr and Cb values to take into account. */
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params->meas.awb_meas_config.min_c = 16;
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/* Number of frames to use to estimate the mean (0 means 1 frame). */
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params->meas.awb_meas_config.frames = 0;
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/* Update AWB measurement unit configuration. */
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params->module_cfg_update |= RKISP1_CIF_ISP_MODULE_AWB;
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/* Make sure the ISP is measuring the means for the next frame. */
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params->module_en_update |= RKISP1_CIF_ISP_MODULE_AWB;
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params->module_ens |= RKISP1_CIF_ISP_MODULE_AWB;
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}
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/**
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* \copydoc libcamera::ipa::Algorithm::process
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*/
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void Awb::process([[maybe_unused]] IPAContext &context, const rkisp1_stat_buffer *stats)
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{
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const rkisp1_cif_isp_stat *params = &stats->params;
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const rkisp1_cif_isp_awb_stat *awb = ¶ms->awb;
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IPAFrameContext &frameContext = context.frameContext;
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/* Get the YCbCr mean values */
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double yMean = awb->awb_mean[0].mean_y_or_g;
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double crMean = awb->awb_mean[0].mean_cr_or_r;
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double cbMean = awb->awb_mean[0].mean_cb_or_b;
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/*
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* Convert from YCbCr to RGB.
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* The hardware uses the following formulas:
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* Y = 16 + 0.2500 R + 0.5000 G + 0.1094 B
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* Cb = 128 - 0.1406 R - 0.2969 G + 0.4375 B
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* Cr = 128 + 0.4375 R - 0.3750 G - 0.0625 B
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*
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* The inverse matrix is thus:
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* [[1,1636, -0,0623, 1,6008]
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* [1,1636, -0,4045, -0,7949]
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* [1,1636, 1,9912, -0,0250]]
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*/
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yMean -= 16;
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cbMean -= 128;
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crMean -= 128;
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double redMean = 1.1636 * yMean - 0.0623 * cbMean + 1.6008 * crMean;
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double greenMean = 1.1636 * yMean - 0.4045 * cbMean - 0.7949 * crMean;
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double blueMean = 1.1636 * yMean + 1.9912 * cbMean - 0.0250 * crMean;
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/* Estimate the red and blue gains to apply in a grey world. */
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double redGain = greenMean / (redMean + 1);
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double blueGain = greenMean / (blueMean + 1);
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/* Filter the values to avoid oscillations. */
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double speed = 0.2;
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redGain = speed * redGain + (1 - speed) * frameContext.awb.gains.red;
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blueGain = speed * blueGain + (1 - speed) * frameContext.awb.gains.blue;
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/*
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* Gain values are unsigned integer value, range 0 to 4 with 8 bit
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* fractional part.
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*/
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frameContext.awb.gains.red = std::clamp(redGain, 0.0, 1023.0 / 256);
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frameContext.awb.gains.blue = std::clamp(blueGain, 0.0, 1023.0 / 256);
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/* Hardcode the green gain to 1.0. */
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frameContext.awb.gains.green = 1.0;
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frameContext.awb.temperatureK = estimateCCT(redMean, greenMean, blueMean);
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LOG(RkISP1Awb, Debug) << "Gain found for red: " << context.frameContext.awb.gains.red
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<< " and for blue: " << context.frameContext.awb.gains.blue;
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}
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} /* namespace ipa::rkisp1::algorithms */
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} /* namespace libcamera */
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