[PATCH v5 3/4] libcamera: software_isp: Add support for contrast control
Kieran Bingham
kieran.bingham at ideasonboard.com
Fri Dec 6 01:26:07 CET 2024
Quoting Kieran Bingham (2024-12-06 00:22:58)
> Quoting Milan Zamazal (2024-11-28 12:52:24)
> > Software ISP is currently fully automatic and doesn't allow image
> > modifications by explicitly set control values. The user has no means
> > to make the image looking better.
> >
> > This patch introduces support for contrast control, which can improve
> > e.g. a flat looking image. Based on the provided contrast value, it
> > applies a simple S-curve modification to the image.
> >
> > The contrast algorithm just handles the provided values, while the
> > S-curve is applied in the gamma algorithm on the computed gamma curve
> > whenever the contrast value changes. Since the algorithm is applied
> > only on the lookup table already present, its overhead is negligible.
> >
> > The contrast value range is 0..2 and corresponds to the whole range from
> > a completely flat contrast to an infinite contrast, 1.0 being the normal
> > value. This makes the user visible range intuitive and easy to use in
> > GUI sliders, while complying with Contrast control definition. There is
> > no unified range in the hardware pipelines, for example rkisp1 uses
> > 0..1.993 range while rpi uses 0..10 range.
> >
> > This is a preparation patch without actually providing the control
> > itself, which is done in the following patch.
> >
> > Signed-off-by: Milan Zamazal <mzamazal at redhat.com>
>
> Well, I've just tested this - and it does indeed affect the image, and
> respond correctly to a slider control in camshark ... so that's progress
> for the soft-isp from my perspective, and I know more will be built on
> top of this:
>
> Tested-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
>
> > ---
> > src/ipa/simple/algorithms/lut.cpp | 40 +++++++++++++++++++++++++++----
> > src/ipa/simple/algorithms/lut.h | 5 ++++
> > src/ipa/simple/ipa_context.h | 7 ++++++
> > 3 files changed, 47 insertions(+), 5 deletions(-)
> >
> > diff --git a/src/ipa/simple/algorithms/lut.cpp b/src/ipa/simple/algorithms/lut.cpp
> > index 9744e773..dd76e117 100644
> > --- a/src/ipa/simple/algorithms/lut.cpp
> > +++ b/src/ipa/simple/algorithms/lut.cpp
> > @@ -9,14 +9,19 @@
> >
> > #include <algorithm>
> > #include <cmath>
> > +#include <optional>
> > #include <stdint.h>
> >
> > #include <libcamera/base/log.h>
> >
> > #include "simple/ipa_context.h"
> >
> > +#include "control_ids.h"
> > +
> > namespace libcamera {
> >
> > +LOG_DEFINE_CATEGORY(IPASoftLut)
> > +
> > namespace ipa::soft::algorithms {
> >
> > int Lut::configure(IPAContext &context,
> > @@ -24,24 +29,48 @@ int Lut::configure(IPAContext &context,
> > {
> > /* Gamma value is fixed */
> > context.configuration.gamma = 0.5;
> > + context.activeState.knobs.contrast = std::optional<double>();
> > updateGammaTable(context);
> >
> > return 0;
> > }
> >
> > +void Lut::queueRequest(typename Module::Context &context,
> > + [[maybe_unused]] const uint32_t frame,
> > + [[maybe_unused]] typename Module::FrameContext &frameContext,
> > + const ControlList &controls)
> > +{
> > + const auto &contrast = controls.get(controls::Contrast);
> > + if (contrast.has_value()) {
> > + context.activeState.knobs.contrast = contrast;
> > + LOG(IPASoftLut, Debug) << "Setting contrast to " << contrast.value();
> > + }
> > +}
> > +
> > void Lut::updateGammaTable(IPAContext &context)
> > {
> > auto &gammaTable = context.activeState.gamma.gammaTable;
> > - auto blackLevel = context.activeState.blc.level;
> > + const auto blackLevel = context.activeState.blc.level;
> > const unsigned int blackIndex = blackLevel * gammaTable.size() / 256;
> > + const auto contrast = context.activeState.knobs.contrast.value_or(1.0);
> >
> > std::fill(gammaTable.begin(), gammaTable.begin() + blackIndex, 0);
> > const float divisor = gammaTable.size() - blackIndex - 1.0;
> > - for (unsigned int i = blackIndex; i < gammaTable.size(); i++)
> > - gammaTable[i] = UINT8_MAX * std::pow((i - blackIndex) / divisor,
> > - context.configuration.gamma);
> > + for (unsigned int i = blackIndex; i < gammaTable.size(); i++) {
> > + double normalized = (i - blackIndex) / divisor;
> > + /* Convert 0..2 to 0..infinity; avoid actual inifinity at tan(pi/2) */
> > + double contrastExp = tan(std::clamp(contrast * M_PI_4, 0.0, M_PI_2 - 0.00001));
> > + /* Apply simple S-curve */
> > + if (normalized < 0.5)
> > + normalized = 0.5 * std::pow(normalized / 0.5, contrastExp);
> > + else
> > + normalized = 1.0 - 0.5 * std::pow((1.0 - normalized) / 0.5, contrastExp);
> > + gammaTable[i] = UINT8_MAX *
> > + std::pow(normalized, context.configuration.gamma);
> > + }
> >
> > context.activeState.gamma.blackLevel = blackLevel;
> > + context.activeState.gamma.contrast = contrast;
It would be nice if both the black level and the contrast were reported
in the metadata of the completed frame.
I guess that can be a patch on top as more work is coming on top of
this, but any control that affects the image should be reporting what
value was applied when that image completes in the request metadata.
--
Kieran
> > }
> >
> > void Lut::prepare(IPAContext &context,
> > @@ -55,7 +84,8 @@ void Lut::prepare(IPAContext &context,
> > * observed, it's not permanently prone to minor fluctuations or
> > * rounding errors.
> > */
> > - if (context.activeState.gamma.blackLevel != context.activeState.blc.level)
> > + if (context.activeState.gamma.blackLevel != context.activeState.blc.level ||
> > + context.activeState.gamma.contrast != context.activeState.knobs.contrast)
> > updateGammaTable(context);
> >
> > auto &gains = context.activeState.gains;
> > diff --git a/src/ipa/simple/algorithms/lut.h b/src/ipa/simple/algorithms/lut.h
> > index b635987d..ef2df147 100644
> > --- a/src/ipa/simple/algorithms/lut.h
> > +++ b/src/ipa/simple/algorithms/lut.h
> > @@ -20,6 +20,11 @@ public:
> > ~Lut() = default;
> >
> > 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,
> > diff --git a/src/ipa/simple/ipa_context.h b/src/ipa/simple/ipa_context.h
> > index fd7343e9..0c2f7021 100644
> > --- a/src/ipa/simple/ipa_context.h
> > +++ b/src/ipa/simple/ipa_context.h
> > @@ -11,6 +11,8 @@
> > #include <optional>
> > #include <stdint.h>
> >
> > +#include <libcamera/controls.h>
> > +
> > #include <libipa/fc_queue.h>
> >
> > namespace libcamera {
> > @@ -48,7 +50,12 @@ struct IPAActiveState {
> > struct {
> > std::array<double, kGammaLookupSize> gammaTable;
> > uint8_t blackLevel;
> > + double contrast;
> > } gamma;
> > + struct {
> > + /* 0..2 range, 1.0 = normal */
> > + std::optional<double> contrast;
> > + } knobs;
> > };
> >
> > struct IPAFrameContext : public FrameContext {
> > --
> > 2.44.2
> >
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