[PATCH 3/7] libcamera: geometry: Add Rectangle::mappedBetween()

[Paul Elder]

On Wed, Nov 20, 2024 at 09:57:42AM +0100, Stefan Klug wrote:
> Handling cropping and scaling within a complicated pipeline involves
> transformations of rectangles between different coordinate systems. For
> example the full input of the dewarper (0,0)/1920x1080 might correspond
> to the rectangle (0, 243)/2592x1458 in sensor coordinates (of a
> 2592x1944 sensor). Add a function that allows the transformation of a
> rectangle defined in one reference frame (dewarper) into the coordinates
> of a second reference frame (sensor).
> 
> Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
> ---
>  include/libcamera/geometry.h |  2 ++
>  src/libcamera/geometry.cpp   | 33 +++++++++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+)
> 
> diff --git a/include/libcamera/geometry.h b/include/libcamera/geometry.h
> index 9ca5865a3d0d..8c5f34f4dec1 100644
> --- a/include/libcamera/geometry.h
> +++ b/include/libcamera/geometry.h
> @@ -299,6 +299,8 @@ public:
>  	__nodiscard Rectangle scaledBy(const Size &numerator,
>  				       const Size &denominator) const;
>  	__nodiscard Rectangle translatedBy(const Point &point) const;
> +
> +	Rectangle mappedBetween(const Rectangle &source, const Rectangle &target) const;
>  };
>  
>  bool operator==(const Rectangle &lhs, const Rectangle &rhs);
> diff --git a/src/libcamera/geometry.cpp b/src/libcamera/geometry.cpp
> index 90ccf8c19f97..7e29fe35801e 100644
> --- a/src/libcamera/geometry.cpp
> +++ b/src/libcamera/geometry.cpp
> @@ -837,6 +837,39 @@ Rectangle Rectangle::translatedBy(const Point &point) const
>  	return { x + point.x, y + point.y, width, height };
>  }
>  
> +/**
> + * \brief Maps a Rectangle from one reference frame to another
> + * \param[in] source The source reference frame
> + * \param[in] destination The destination reference frame
> + *
> + * The params source and destinations specify two reference frames for the same

iirc you can do \a source and \a destination

With that fixed,

Reviewed-by: Paul Elder <paul.elder at ideasonboard.com>

> + * data. The rectangle is translated from the source reference frame into the
> + * destination reference frame.
> + *
> + * For example, consider a sensor with a resolution of 2592x1458 pixels and a
> + * assume a rectangle of (0, 243)/2592x1458 (sensorFrame) in sensor coordinates
> + * is mapped to a rectangle (0,0)/(1920,1080) (displayFrame) in display
> + * coordinates. This function can be used to transform an arbitrary rectangle
> + * from display coordinates to sensor coordinates or vice versa:
> + *
> + * \code{.cpp}
> + * displayRect = sensorRect.mappedBetween(sensorFrame, displayFrame);
> + * \endcode
> + */
> +Rectangle Rectangle::mappedBetween(const Rectangle &source,
> +				   const Rectangle &destination) const
> +{
> +	Rectangle r;
> +	double sx = static_cast<double>(destination.width) / source.width;
> +	double sy = static_cast<double>(destination.height) / source.height;
> +
> +	r.x = static_cast<int>((x - source.x) * sx) + destination.x;
> +	r.y = static_cast<int>((y - source.y) * sy) + destination.y;
> +	r.width = static_cast<int>(width * sx);
> +	r.height = static_cast<int>(height * sy);
> +	return r;
> +}
> +
>  /**
>   * \brief Compare rectangles for equality
>   * \return True if the two rectangles are equal, false otherwise
> -- 
> 2.43.0
>