[PATCH] libcamera: matrix: Add read-only accessor to internal data

[Kieran Bingham]

Quoting Laurent Pinchart (2025-01-27 06:47:45)
> Add a data() function to the Matrix class to access the internal data.
> This is useful for code that needs to use the matrix contents as a
> linear array, as shows by the RkISP1::Ccm::process() function that needs

s/shows/shown/

> to copy the matrix data to a local variable. Simplify that function by
> using the new accessor.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> ---
>  include/libcamera/internal/matrix.h | 2 ++
>  src/ipa/rkisp1/algorithms/ccm.cpp   | 7 +------
>  src/libcamera/matrix.cpp            | 6 ++++++
>  3 files changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/include/libcamera/internal/matrix.h b/include/libcamera/internal/matrix.h
> index 7a71028c473a..a055e6926c94 100644
> --- a/include/libcamera/internal/matrix.h
> +++ b/include/libcamera/internal/matrix.h
> @@ -66,6 +66,8 @@ public:
>                 return out.str();
>         }
>  
> +       Span<const T, Rows * Cols> data() const { return data_; }
> +
>         Span<const T, Cols> operator[](size_t i) const
>         {
>                 return Span<const T, Cols>{ &data_.data()[i * Cols], Cols };
> diff --git a/src/ipa/rkisp1/algorithms/ccm.cpp b/src/ipa/rkisp1/algorithms/ccm.cpp
> index e2b5cf4d313e..eb8ca39e56a8 100644
> --- a/src/ipa/rkisp1/algorithms/ccm.cpp
> +++ b/src/ipa/rkisp1/algorithms/ccm.cpp
> @@ -120,12 +120,7 @@ void Ccm::process([[maybe_unused]] IPAContext &context,
>                   [[maybe_unused]] const rkisp1_stat_buffer *stats,
>                   ControlList &metadata)
>  {
> -       float m[9];
> -       for (unsigned int i = 0; i < 3; i++) {
> -               for (unsigned int j = 0; j < 3; j++)
> -                       m[i * 3 + j] = frameContext.ccm.ccm[i][j];
> -       }
> -       metadata.set(controls::ColourCorrectionMatrix, m);
> +       metadata.set(controls::ColourCorrectionMatrix, frameContext.ccm.ccm.data());

That's better than iterating 3x3.


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

>  }
>  
>  REGISTER_IPA_ALGORITHM(Ccm, "Ccm")
> diff --git a/src/libcamera/matrix.cpp b/src/libcamera/matrix.cpp
> index 4d95a19bfbb9..d9d34867b0a3 100644
> --- a/src/libcamera/matrix.cpp
> +++ b/src/libcamera/matrix.cpp
> @@ -52,6 +52,12 @@ LOG_DEFINE_CATEGORY(Matrix)
>   * \return A string describing the matrix
>   */
>  
> +/**
> + * \fn Matrix::data()
> + * \brief Access the internal data as a linear array
> + * \return A span referencing the internal data as a linear array
> + */
> +
>  /**
>   * \fn Span<const T, Cols> Matrix::operator[](size_t i) const
>   * \brief Index to a row in the matrix
> 
> base-commit: 8aef7b4dfb12f2f9bf0513625231b85a5b8f5440
> -- 
> Regards,
> 
> Laurent Pinchart
>