libcamera/src/ipa/ipu3/algorithms/tone_mapping.cpp
Jean-Michel Hautbois a1f0df8654 ipa: ipu3: tonemapping: Add the documentation for ToneMapping
The tone mapping algorithm is currently undocumented.

Provide an introduction and overview to the implementation as the class
definition and document how the algorithm operates in the process and
prepare methods.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
2021-10-26 14:03:37 +02:00

109 lines
2.7 KiB
C++

/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2021, Google inc.
*
* tone_mapping.cpp - IPU3 ToneMapping and Gamma control
*/
#include "tone_mapping.h"
#include <cmath>
#include <string.h>
/**
* \file tone_mapping.h
*/
namespace libcamera {
namespace ipa::ipu3::algorithms {
/**
* \class ToneMapping
* \brief A class to handle tone mapping based on gamma
*
* This algorithm improves the image dynamic using a look-up table which is
* generated based on a gamma parameter.
*/
ToneMapping::ToneMapping()
: gamma_(1.0)
{
}
/**
* \brief Configure the tone mapping given a configInfo
* \param[in] context The shared IPA context
* \param[in] configInfo The IPA configuration data
*
* \return 0
*/
int ToneMapping::configure(IPAContext &context,
[[maybe_unused]] const IPAConfigInfo &configInfo)
{
/* Initialise tone mapping gamma value. */
context.frameContext.toneMapping.gamma = 0.0;
return 0;
}
/**
* \brief Fill in the parameter structure, and enable gamma control
* \param context The shared IPA context
* \param params The IPU3 parameters
*
* Populate the IPU3 parameter structure with our tone mapping look up table and
* enable the gamma control module in the processing blocks.
*/
void ToneMapping::prepare([[maybe_unused]] IPAContext &context,
ipu3_uapi_params *params)
{
/* Copy the calculated LUT into the parameters buffer. */
memcpy(params->acc_param.gamma.gc_lut.lut,
context.frameContext.toneMapping.gammaCorrection.lut,
IPU3_UAPI_GAMMA_CORR_LUT_ENTRIES *
sizeof(params->acc_param.gamma.gc_lut.lut[0]));
/* Enable the custom gamma table. */
params->use.acc_gamma = 1;
params->acc_param.gamma.gc_ctrl.enable = 1;
}
/**
* \brief Calculate the tone mapping look up table
* \param context The shared IPA context
* \param stats The IPU3 statistics and ISP results
*
* The tone mapping look up table is generated as an inverse power curve from
* our gamma setting.
*/
void ToneMapping::process(IPAContext &context,
[[maybe_unused]] const ipu3_uapi_stats_3a *stats)
{
/*
* Hardcode gamma to 1.1 as a default for now.
*
* \todo Expose gamma control setting through the libcamera control API
*/
gamma_ = 1.1;
if (context.frameContext.toneMapping.gamma == gamma_)
return;
struct ipu3_uapi_gamma_corr_lut &lut =
context.frameContext.toneMapping.gammaCorrection;
for (uint32_t i = 0; i < std::size(lut.lut); i++) {
double j = static_cast<double>(i) / (std::size(lut.lut) - 1);
double gamma = std::pow(j, 1.0 / gamma_);
/* The output value is expressed on 13 bits. */
lut.lut[i] = gamma * 8191;
}
context.frameContext.toneMapping.gamma = gamma_;
}
} /* namespace ipa::ipu3::algorithms */
} /* namespace libcamera */