[PATCH v2 1/4] ipa: rkisp1: Add gamma algorithm

[Kieran Bingham]

Quoting Stefan Klug (2024-05-22 15:54:35)
> Add a gamma algorithm for the rkisp1. It defaults to a gamma of 2.2 which
> closely resembles sRGB.  No seperate sRGB mode was implemented because the pwl
> that models the gamma curve is so coarse that there is basically no difference
> between srgb and gamma=2.2
> 
> The gamma algorithm is not enabled by default. This will be done in future
> tuning file updates.
> 
> Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
> ---
> 
> Note:
> 
> This patch breaks the naming conventions. It is implemented inside goc.h/cpp
> because the hardware block and params inside the rkisp1 are called "goc". The
> class itself is called Gamma, and the algorithm is registered with the name
> "Gamma". The idea was that similar functionalities should be named the same
> inside the tuning files (even among multipe isps).  It still feels a bit
> awkward. So thoughts are welcome :-)
> 
> 
> v1 -> v2:
> - fixed some style issues
> - fail in case of a V12 isp
> 
>  src/ipa/rkisp1/algorithms/goc.cpp     | 100 ++++++++++++++++++++++++++
>  src/ipa/rkisp1/algorithms/goc.h       |  32 +++++++++
>  src/ipa/rkisp1/algorithms/meson.build |   1 +
>  3 files changed, 133 insertions(+)
>  create mode 100644 src/ipa/rkisp1/algorithms/goc.cpp
>  create mode 100644 src/ipa/rkisp1/algorithms/goc.h
> 
> diff --git a/src/ipa/rkisp1/algorithms/goc.cpp b/src/ipa/rkisp1/algorithms/goc.cpp
> new file mode 100644
> index 00000000..6f313820
> --- /dev/null
> +++ b/src/ipa/rkisp1/algorithms/goc.cpp
> @@ -0,0 +1,100 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2024, Ideas On Board
> + *
> + * RkISP1 Gamma out control
> + */
> +#include "goc.h"
> +
> +#include <cmath>
> +
> +#include <libcamera/base/log.h>
> +#include <libcamera/base/utils.h>
> +
> +#include "libcamera/internal/yaml_parser.h"
> +
> +#include "linux/rkisp1-config.h"
> +
> +/**
> + * \file goc.h
> + */
> +
> +namespace libcamera {
> +
> +namespace ipa::rkisp1::algorithms {
> +
> +/**
> + * \class Gamma
> + * \brief RkISP1 Gamma out control
> + *
> + * This algorithm implements the gamma out curve for the RkISP1.
> + * It defaults to a gamma value of 2.2
> + * As gamma is internally represented as a piecewise linear function with only
> + * 16 knots, the difference between gamma=2.2 and sRGB gamma is minimal.
> + * Therefore sRGB gamma was not implemented as special case.
> + *
> + * Useful links:
> + * https://www.cambridgeincolour.com/tutorials/gamma-correction.htm
> + * https://en.wikipedia.org/wiki/SRGB
> + */
> +
> +LOG_DEFINE_CATEGORY(RkISP1Gamma)
> +
> +Gamma::Gamma()
> +{
> +}

I see this and think why not = default ... but I see it gets updated
later ...

> +
> +/**
> + * \copydoc libcamera::ipa::Algorithm::init
> + */
> +int Gamma::init([[maybe_unused]] IPAContext &context,
> +               [[maybe_unused]] const YamlObject &tuningData)
> +{
> +       if (context.hw->numGammaOutSamples !=
> +           RKISP1_CIF_ISP_GAMMA_OUT_MAX_SAMPLES_V10) {
> +               LOG(RkISP1Gamma, Error)
> +                       << "Gamma is not implemented for RkISP1 V12";
> +               return -EINVAL;
> +       }
> +
> +       return 0;
> +}
> +
> +/**
> + * \copydoc libcamera::ipa::Algorithm::prepare
> + */
> +void Gamma::prepare([[maybe_unused]] IPAContext &context,
> +                   const uint32_t frame,
> +                   [[maybe_unused]] IPAFrameContext &frameContext,
> +                   rkisp1_params_cfg *params)
> +{
> +       /* The logarithmic segments as specified in the reference.

	/*
	 * nit: multiline comments have an empty first and last
	 * line for the leading '/*' and trailing '*/'
	 */

> +        * Plus an additional 0 to make the loop easier
> +        */
> +       int segments[] = { 64, 64, 64, 64, 128, 128, 128, 128, 256, 256, 256,
> +                          512, 512, 512, 512, 512, 0 };
> +       auto gamma_y = params->others.goc_config.gamma_y;
> +
> +       ASSERT(context.hw->numGammaOutSamples ==
> +              RKISP1_CIF_ISP_GAMMA_OUT_MAX_SAMPLES_V10);
> +
> +       if (frame > 0)
> +               return;
> +
> +       int x = 0;
> +       for (unsigned i = 0; i < context.hw->numGammaOutSamples; i++) {
> +               gamma_y[i] = std::pow(x / 4096.0, 1.0 / gamma_) * 1023.0;
> +               x += segments[i];
> +       }
> +
> +       params->others.goc_config.mode = RKISP1_CIF_ISP_GOC_MODE_LOGARITHMIC;
> +       params->module_en_update |= RKISP1_CIF_ISP_MODULE_GOC;
> +       params->module_ens |= RKISP1_CIF_ISP_MODULE_GOC;
> +       params->module_cfg_update |= RKISP1_CIF_ISP_MODULE_GOC;
> +}
> +
> +REGISTER_IPA_ALGORITHM(Gamma, "Gamma")
> +
> +} /* namespace ipa::rkisp1::algorithms */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/rkisp1/algorithms/goc.h b/src/ipa/rkisp1/algorithms/goc.h
> new file mode 100644
> index 00000000..fe7caba3
> --- /dev/null
> +++ b/src/ipa/rkisp1/algorithms/goc.h
> @@ -0,0 +1,32 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2024, Ideas On Board
> + *
> + * RkISP1 Gamma out control
> + */
> +
> +#pragma once
> +
> +#include "algorithm.h"
> +
> +namespace libcamera {
> +
> +namespace ipa::rkisp1::algorithms {
> +
> +class Gamma : public Algorithm
> +{
> +public:
> +       Gamma();
> +       ~Gamma() = default;
> +
> +       int init(IPAContext &context, const YamlObject &tuningData) override;
> +       void prepare(IPAContext &context, const uint32_t frame,
> +                    IPAFrameContext &frameContext,
> +                    rkisp1_params_cfg *params) override;
> +
> +private:
> +       float gamma_ = 2.2;
> +};
> +
> +} /* namespace ipa::rkisp1::algorithms */
> +} /* namespace libcamera */
> diff --git a/src/ipa/rkisp1/algorithms/meson.build b/src/ipa/rkisp1/algorithms/meson.build
> index 93a48329..6ee71a9b 100644
> --- a/src/ipa/rkisp1/algorithms/meson.build
> +++ b/src/ipa/rkisp1/algorithms/meson.build
> @@ -8,6 +8,7 @@ rkisp1_ipa_algorithms = files([
>      'dpcc.cpp',
>      'dpf.cpp',
>      'filter.cpp',
> +    'goc.cpp',
>      'gsl.cpp',
>      'lsc.cpp',
>  ])
> -- 
> 2.40.1
>