[v15,2/6] libcamera: software_isp: Add LSC data to DebayerParams

28106 diff mbox series

From: Xander Pronk <xander.c.pronk@gmail.com>

Add a lookup table for grid-based lens shading correction to debayer
params.  The lookup table is in the format of an RGBA texture to be
passed to debayering.  The alpha value serves only for padding and can
be arbitrary; OpenGL wants by default rows aligned to 4 bytes and using
RGBA format is the simplest way to achieve it.

The parameter is filled in by Lsc algorithm implemented in a follow-up
patch.  If the algorithm is not enabled, the table is filled in with
values corresponding to identity multiplication (1.0).

In order the image processing would be able to update its internal
data (e.g. the GPU texture) on and only on the lookup table changes,
lscLutVersion parameter is added, which is incremented on each lookup
table change.

The parameters are currently unused, their handling is implemented in
follow-up patches.

The grid size is selected to be the same as in the tuning files already
present in rkisp1.  Another popular grid size in other pipelines is 32.

Co-developed-by: Rick ten Wolde <rick_libcamera@wolde.info>
Signed-off-by: Rick ten Wolde <rick_libcamera@wolde.info>
Signed-off-by: Xander Pronk <xander.c.pronk@gmail.com>
Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
---
 .../internal/software_isp/debayer_params.h    | 13 +++++++++
 src/libcamera/software_isp/debayer.cpp        | 28 +++++++++++++++++++
 2 files changed, 41 insertions(+)

Quoting Milan Zamazal (2026-08-26 19:19:49)
> From: Xander Pronk <xander.c.pronk@gmail.com>
> 
> Add a lookup table for grid-based lens shading correction to debayer
> params.  The lookup table is in the format of an RGBA texture to be
> passed to debayering.  The alpha value serves only for padding and can
> be arbitrary; OpenGL wants by default rows aligned to 4 bytes and using
> RGBA format is the simplest way to achieve it.
> 
> The parameter is filled in by Lsc algorithm implemented in a follow-up
> patch.  If the algorithm is not enabled, the table is filled in with
> values corresponding to identity multiplication (1.0).
> 
> In order the image processing would be able to update its internal
> data (e.g. the GPU texture) on and only on the lookup table changes,
> lscLutVersion parameter is added, which is incremented on each lookup
> table change.
> 
> The parameters are currently unused, their handling is implemented in
> follow-up patches.
> 
> The grid size is selected to be the same as in the tuning files already
> present in rkisp1.  Another popular grid size in other pipelines is 32.


Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

I'm keen to get this series in now for 0.8.

As far as I can tell, there's no possible regressions in this series,
and CI is only blocked on the merge check from some missing tags. Lets
fix that:


Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

> 
> Co-developed-by: Rick ten Wolde <rick_libcamera@wolde.info>
> Signed-off-by: Rick ten Wolde <rick_libcamera@wolde.info>
> Signed-off-by: Xander Pronk <xander.c.pronk@gmail.com>
> Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
> ---
>  .../internal/software_isp/debayer_params.h    | 13 +++++++++
>  src/libcamera/software_isp/debayer.cpp        | 28 +++++++++++++++++++
>  2 files changed, 41 insertions(+)
> 
> diff --git a/include/libcamera/internal/software_isp/debayer_params.h b/include/libcamera/internal/software_isp/debayer_params.h
> index 1074720d7..0d9196874 100644
> --- a/include/libcamera/internal/software_isp/debayer_params.h
> +++ b/include/libcamera/internal/software_isp/debayer_params.h
> @@ -10,6 +10,7 @@
>  
>  #pragma once
>  
> +#include <array>
>  #include <stdint.h>
>  
>  #include "libcamera/internal/matrix.h"
> @@ -25,6 +26,18 @@ struct DebayerParams {
>         float gamma = 1.0;
>         float contrastExp = 1.0;
>         RGB<double> gains = RGB<double>({ 1.0, 1.0, 1.0 });
> +
> +       /**
> +        * To prevent OpenGL alignment issues, the number of bytes in each row
> +        * must be a multiple of 4 (the initial value of GL_UNPACK_ALIGNMENT)
> +        * and lscLut is also aligned to 4 bytes.
> +        **/
> +       static constexpr unsigned int kLscGridSize = 17;
> +       static constexpr unsigned int kLscValuesPerCell = 4;
> +       using LscLookupTable =
> +               std::array<uint8_t, kLscGridSize * kLscGridSize * kLscValuesPerCell>;
> +       alignas(4) LscLookupTable lscLut{};
> +       uint64_t lscLutVersion = 0;
>  };
>  
>  } /* namespace libcamera */
> diff --git a/src/libcamera/software_isp/debayer.cpp b/src/libcamera/software_isp/debayer.cpp
> index a4854e51b..82cdf1dc2 100644
> --- a/src/libcamera/software_isp/debayer.cpp
> +++ b/src/libcamera/software_isp/debayer.cpp
> @@ -43,6 +43,34 @@ namespace libcamera {
>   * \brief Contrast value to be used as an exponent
>   */
>  
> +/**
> + * \var DebayerParams::kLscGridSize
> + * \brief Number of lens shading grid areas in one direction
> + */
> +
> +/**
> + * \var DebayerParams::kLscValuesPerCell
> + * \brief Number of pixel values per each of the lens shading grid areas
> + */
> +
> +/**
> + * \typedef DebayerParams::LscLookupTable
> + * \brief Lookup table for lens shading correction
> + *
> + * It's an array of values to be later used as a texture.
> + * The values are in row - column - RGB order.
> + */
> +
> +/**
> + * \var DebayerParams::lscLut
> + * \brief Lens shading lookup table
> + */
> +
> +/**
> + * \var DebayerParams::lscLutVersion
> + * \brief Incremented on each \a lscLut change
> + */
> +
>  /**
>   * \class Debayer
>   * \brief Base debayering class
> -- 
> 2.55.0
>