Hi Milan,
Thank you for the patch.
On Tue, Nov 26, 2024 at 10:15:04AM +0100, Milan Zamazal wrote:
> 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 with a
> range 0..infinity and 1.0 being the normal 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.
Isn't contrast defined as a multiplier ? Applying a different luminance
transformation and calling it contrast will make different cameras
behave in different ways.
> 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>
> ---
> src/ipa/simple/algorithms/lut.cpp | 38 +++++++++++++++++++++++++++----
> src/ipa/simple/algorithms/lut.h | 5 ++++
> src/ipa/simple/ipa_context.h | 7 ++++++
> 3 files changed, 45 insertions(+), 5 deletions(-)
>
> diff --git a/src/ipa/simple/algorithms/lut.cpp b/src/ipa/simple/algorithms/lut.cpp
> index 9744e773a..ffded0594 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 +29,46 @@ 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;
> + /* Apply simple S-curve */
> + if (normalized < 0.5)
> + normalized = 0.5 * std::pow(normalized / 0.5, contrast);
> + else
> + normalized = 1.0 - 0.5 * std::pow((1.0 - normalized) / 0.5, contrast);
> + gammaTable[i] = UINT8_MAX *
> + std::pow(normalized, context.configuration.gamma);
> + }
>
> context.activeState.gamma.blackLevel = blackLevel;
> + context.activeState.gamma.contrast = contrast;
> }
>
> void Lut::prepare(IPAContext &context,
> @@ -55,7 +82,8 @@ 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 b635987d0..ef2df147c 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 fd7343e91..148052207 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..inf range, 1.0 = normal */
> + std::optional<double> contrast;
> + } knobs;
> };
>
> struct IPAFrameContext : public FrameContext {
--
Regards,
Laurent Pinchart