[PATCH v2 1/1] libcamera: software_isp: Add saturation control
Paul Elder
paul.elder at ideasonboard.com
Tue May 13 16:36:12 CEST 2025
Hi Milan,
Thanks for the patch.
Quoting Milan Zamazal (2025-04-30 13:20:42)
> Saturation control is added on top of the colour correction matrix. A
> way of saturation adjustment that can be fully integrated into the
s/way/method/ I think would be clearer (without having to reorganize the entire
sentence)
> colour correction matrix is used. The control is available only if Ccm
> algorithm is enabled.
>
> The control uses 0.0-2.0 value range, with 1.0 being unmodified
> saturation, 0.0 full desaturation and 2.0 quite saturated.
>
> The saturation is adjusted by converting to Y'CbCr colour space,
> applying the saturation value on the colour axes, and converting back to
> RGB. ITU-R BT.601 conversion is used to convert between the colour
> spaces, for no particular reason.
>
> The colour correction matrix is applied before gamma and the given
> matrix is suitable for such a case. Alternatively, the transformation
> used in libcamera rpi ccm.cpp could be used.
>
> Signed-off-by: Milan Zamazal <mzamazal at redhat.com>
> ---
> src/ipa/simple/algorithms/ccm.cpp | 60 +++++++++++++++++++++++++++++--
> src/ipa/simple/algorithms/ccm.h | 11 ++++++
> src/ipa/simple/ipa_context.h | 4 +++
> 3 files changed, 72 insertions(+), 3 deletions(-)
>
> diff --git a/src/ipa/simple/algorithms/ccm.cpp b/src/ipa/simple/algorithms/ccm.cpp
> index d5ba928d..021aefc9 100644
> --- a/src/ipa/simple/algorithms/ccm.cpp
> +++ b/src/ipa/simple/algorithms/ccm.cpp
> @@ -3,7 +3,7 @@
> * Copyright (C) 2024, Ideas On Board
> * Copyright (C) 2024-2025, Red Hat Inc.
> *
> - * Color correction matrix
> + * Color correction matrix + saturation
> */
>
> #include "ccm.h"
> @@ -13,6 +13,8 @@
>
> #include <libcamera/control_ids.h>
>
> +#include "libcamera/internal/matrix.h"
> +
> namespace {
>
> constexpr unsigned int kTemperatureThreshold = 100;
> @@ -35,28 +37,77 @@ int Ccm::init([[maybe_unused]] IPAContext &context, const YamlObject &tuningData
> }
>
> context.ccmEnabled = true;
> + context.ctrlMap[&controls::Saturation] = ControlInfo(0.0f, 2.0f, 1.0f);
> +
> + return 0;
> +}
> +
> +int Ccm::configure(IPAContext &context,
> + [[maybe_unused]] const IPAConfigInfo &configInfo)
> +{
> + context.activeState.knobs.saturation = std::optional<double>();
>
> return 0;
> }
>
> +void Ccm::queueRequest(typename Module::Context &context,
> + [[maybe_unused]] const uint32_t frame,
> + [[maybe_unused]] typename Module::FrameContext &frameContext,
> + const ControlList &controls)
> +{
> + const auto &saturation = controls.get(controls::Saturation);
> + if (saturation.has_value()) {
> + context.activeState.knobs.saturation = saturation;
> + LOG(IPASoftCcm, Debug) << "Setting saturation to " << saturation.value();
> + }
> +}
> +
> +void Ccm::updateSaturation(Matrix<float, 3, 3> &ccm, float saturation)
I think applySaturation might be a more appropriate name. updateSaturation
sounds like saturation is the output value and it gets updated based on some
input.
> +{
> + /* https://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.601_conversion */
> + const Matrix<float, 3, 3> rgb2ycbcr{
> + { 0.256788235294, 0.504129411765, 0.0979058823529,
> + -0.148223529412, -0.290992156863, 0.439215686275,
> + 0.439215686275, -0.367788235294, -0.0714274509804 }
> + };
> + const Matrix<float, 3, 3> ycbcr2rgb{
> + { 1.16438356164, 0, 1.59602678571,
> + 1.16438356164, -0.391762290094, -0.812967647235,
> + 1.16438356164, 2.01723214285, 0 }
> + };
> + const Matrix<float, 3, 3> saturationMatrix{
> + { 1, 0, 0,
> + 0, saturation, 0,
> + 0, 0, saturation }
> + };
> + ccm = ycbcr2rgb * saturationMatrix * rgb2ycbcr * ccm;
> +}
> +
> void Ccm::prepare(IPAContext &context, const uint32_t frame,
> IPAFrameContext &frameContext, [[maybe_unused]] DebayerParams *params)
> {
> + auto &saturation = context.activeState.knobs.saturation;
> +
> const unsigned int ct = context.activeState.awb.temperatureK;
>
> - /* Change CCM only on bigger temperature changes. */
> + /* Change CCM only on saturation or bigger temperature changes. */
> if (frame > 0 &&
> - utils::abs_diff(ct, lastCt_) < kTemperatureThreshold) {
> + utils::abs_diff(ct, lastCt_) < kTemperatureThreshold &&
> + saturation == lastSaturation_) {
> frameContext.ccm.ccm = context.activeState.ccm.ccm;
> context.activeState.ccm.changed = false;
> return;
> }
>
> lastCt_ = ct;
> + lastSaturation_ = saturation;
> Matrix<float, 3, 3> ccm = ccm_.getInterpolated(ct);
> + if (saturation)
> + updateSaturation(ccm, saturation.value());
>
> context.activeState.ccm.ccm = ccm;
> frameContext.ccm.ccm = ccm;
> + frameContext.saturation = saturation;
> context.activeState.ccm.changed = true;
> }
>
> @@ -67,6 +118,9 @@ void Ccm::process([[maybe_unused]] IPAContext &context,
> ControlList &metadata)
> {
> metadata.set(controls::ColourCorrectionMatrix, frameContext.ccm.ccm.data());
> +
> + const auto &saturation = frameContext.saturation;
> + metadata.set(controls::Saturation, saturation.value_or(1.0));
> }
>
> REGISTER_IPA_ALGORITHM(Ccm, "Ccm")
> diff --git a/src/ipa/simple/algorithms/ccm.h b/src/ipa/simple/algorithms/ccm.h
> index f4e2b85b..2c5d2170 100644
> --- a/src/ipa/simple/algorithms/ccm.h
> +++ b/src/ipa/simple/algorithms/ccm.h
> @@ -7,6 +7,8 @@
>
> #pragma once
>
> +#include <optional>
> +
> #include "libcamera/internal/matrix.h"
>
> #include <libipa/interpolator.h>
> @@ -24,6 +26,12 @@ public:
> ~Ccm() = default;
>
> int init(IPAContext &context, const YamlObject &tuningData) override;
> + int configure(IPAContext &context,
> + const IPAConfigInfo &configInfo) override;
> + void queueRequest(typename Module::Context &context,
> + const uint32_t frame,
> + typename Module::FrameContext &frameContext,
> + const ControlList &controls) override;
> void prepare(IPAContext &context,
> const uint32_t frame,
> IPAFrameContext &frameContext,
> @@ -34,7 +42,10 @@ public:
> ControlList &metadata) override;
>
> private:
> + void updateSaturation(Matrix<float, 3, 3> &ccm, float saturation);
> +
> unsigned int lastCt_;
> + std::optional<float> lastSaturation_;
> Interpolator<Matrix<float, 3, 3>> ccm_;
> };
>
> diff --git a/src/ipa/simple/ipa_context.h b/src/ipa/simple/ipa_context.h
> index 88cc6c35..56792981 100644
> --- a/src/ipa/simple/ipa_context.h
> +++ b/src/ipa/simple/ipa_context.h
> @@ -63,6 +63,7 @@ struct IPAActiveState {
> struct {
> /* 0..2 range, 1.0 = normal */
> std::optional<double> contrast;
> + std::optional<double> saturation;
Is there a reason why this is double while lastSaturation_ is float? The
Saturation control is also float.
> } knobs;
> };
>
> @@ -75,11 +76,14 @@ struct IPAFrameContext : public FrameContext {
> int32_t exposure;
> double gain;
> } sensor;
> +
> struct {
> double red;
> double blue;
> } gains;
> +
> std::optional<double> contrast;
> + std::optional<double> saturation;
Same here.
Otherwise, looks good.
Thanks,
Paul
> };
>
> struct IPAContext {
> --
> 2.49.0
>
More information about the libcamera-devel
mailing list