[PATCH 01/10] libcamera: matrix: Add cast function

[Laurent Pinchart]

Hi Stefan,

Thank you for the patch.

On Mon, Feb 17, 2025 at 11:01:42AM +0100, Stefan Klug wrote:
> The libcamera code base uses matrices and vectors of type float and
> double. Add a cast function to easily convert between different
> underlying types.

Should we standardize on one of the floating point precisions to avoid
casts ?

> Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
> ---
>  include/libcamera/internal/matrix.h | 11 +++++++++++
>  src/libcamera/matrix.cpp            | 10 ++++++++++
>  2 files changed, 21 insertions(+)
> 
> diff --git a/include/libcamera/internal/matrix.h b/include/libcamera/internal/matrix.h
> index a055e6926c94..ca81dcda93c4 100644
> --- a/include/libcamera/internal/matrix.h
> +++ b/include/libcamera/internal/matrix.h
> @@ -90,6 +90,17 @@ public:
>  		return *this;
>  	}
>  
> +	template<typename T2>
> +	Matrix<T2, Rows, Cols> cast() const

I wonder if we should use a "copy" constructor instead of a cast()
function, to make it clear a copy iw made.

> +	{
> +		Matrix<T2, Rows, Cols> ret;
> +		for (unsigned int i = 0; i < Rows; i++)
> +			for (unsigned int j = 0; j < Cols; j++)
> +				ret[i][j] = static_cast<T2>((*this)[i][j]);

You can operator on data_ directly, with a single loop.

> +
> +		return ret;
> +	}
> +
>  private:
>  	std::array<T, Rows * Cols> data_;
>  };
> diff --git a/src/libcamera/matrix.cpp b/src/libcamera/matrix.cpp
> index e7e027225666..91a3f16405a3 100644
> --- a/src/libcamera/matrix.cpp
> +++ b/src/libcamera/matrix.cpp
> @@ -77,6 +77,16 @@ LOG_DEFINE_CATEGORY(Matrix)
>   * \return Row \a i from the matrix, as a Span
>   */
>  
> +/**
> + * \fn template<typename T2> Matrix<T2, Rows, Cols> Matrix::cast() const
> + * \brief Cast the matrix to a different type
> + *
> + * This function returns a new matrix with the same size and values but a
> + * different type.
> + *
> + * \return The new matrix
> + */
> +
>  /**
>   * \fn Matrix::operator[](size_t i)
>   * \copydoc Matrix::operator[](size_t i) const

-- 
Regards,

Laurent Pinchart