[libcamera-devel] [PATCH v3 4/6] libcamera: Add geometry helper functions

[Kieran Bingham]

Hi David,

On 29/09/2020 17:39, David Plowman wrote:
> These functions are aimed at making it easier to calculate cropping
> rectangles, particularly in order to implement digital zoom.

Personally, I love seeing these helpers grow ;-)

> Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
> Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>

Some minor spelling errors below, but with those fixed:

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

> ---
>  include/libcamera/geometry.h |  20 ++++++
>  src/libcamera/geometry.cpp   | 129 +++++++++++++++++++++++++++++++++++
>  2 files changed, 149 insertions(+)
> 
> diff --git a/include/libcamera/geometry.h b/include/libcamera/geometry.h
> index 02fb63c0..0447ee3e 100644
> --- a/include/libcamera/geometry.h
> +++ b/include/libcamera/geometry.h
> @@ -13,6 +13,8 @@
>  
>  namespace libcamera {
>  
> +class Rectangle;
> +
>  class Size
>  {
>  public:
> @@ -93,8 +95,17 @@ public:
>  			std::max(height, expand.height)
>  		};
>  	}
> +
> +	Size alignedDownToAspectRatio(const Size &ratio) const;
> +	Size alignedUpToAspectRatio(const Size &ratio) const;
> +
> +	Rectangle centredTo(const Rectangle &region,
> +			    int offsetX = 0, int offsetY = 0) const;
>  };
>  
> +Size operator*(const Size &size, float f);
> +Size operator/(const Size &size, float f);
> +
>  bool operator==(const Size &lhs, const Size &rhs);
>  bool operator<(const Size &lhs, const Size &rhs);
>  
> @@ -176,6 +187,11 @@ public:
>  	{
>  	}
>  
> +	constexpr explicit Rectangle(const Size &size)
> +		: x(0), y(0), width(size.width), height(size.height)
> +	{
> +	}
> +
>  	int x;
>  	int y;
>  	unsigned int width;
> @@ -183,6 +199,10 @@ public:
>  
>  	bool isNull() const { return !width && !height; }
>  	const std::string toString() const;
> +
> +	Size size() const;
> +
> +	Rectangle boundedTo(const Rectangle &boundary) const;
>  };
>  
>  bool operator==(const Rectangle &lhs, const Rectangle &rhs);
> diff --git a/src/libcamera/geometry.cpp b/src/libcamera/geometry.cpp
> index b12e1a62..649ee179 100644
> --- a/src/libcamera/geometry.cpp
> +++ b/src/libcamera/geometry.cpp
> @@ -143,6 +143,88 @@ const std::string Size::toString() const
>   * height of this size and the \a expand size
>   */
>  
> +/**
> + * \brief Align down to the aspect ratio given by \a ratio
> + * \param[in] ratio The size whose aspect ratio to align down to
> + * \return A Size whose width and height are equal to the width and height
> + * of this Size aligned down to the aspect ratio of \a ratio
> + */
> +Size Size::alignedDownToAspectRatio(const Size &ratio) const
> +{
> +	uint64_t ratio1 = static_cast<uint64_t>(width) *
> +			  static_cast<uint64_t>(ratio.height);
> +	uint64_t ratio2 = static_cast<uint64_t>(ratio.width) *
> +			  static_cast<uint64_t>(height);
> +
> +	if (ratio1 > ratio2)
> +		return { static_cast<unsigned int>(ratio2 / ratio.height), height };
> +	else
> +		return { width, static_cast<unsigned int>(ratio1 / ratio.width) };
> +}
> +
> +/**
> + * \brief Align up to the aspect ratio given by \a ratio
> + * \param[in] ratio The size whose aspect ratio to align up to
> + * \return A Size whose width and height are equal to the width and height
> + * of this Size aligned up to the aspect ratio of \a ratio
> + */
> +Size Size::alignedUpToAspectRatio(const Size &ratio) const
> +{
> +	uint64_t ratio1 = static_cast<uint64_t>(width) *
> +			  static_cast<uint64_t>(ratio.height);
> +	uint64_t ratio2 = static_cast<uint64_t>(ratio.width) *
> +			  static_cast<uint64_t>(height);
> +
> +	if (ratio1 < ratio2)
> +		return { static_cast<unsigned int>(ratio2 / ratio.height), height };
> +	else
> +		return { width, static_cast<unsigned int>(ratio1 / ratio.width) };
> +}
> +
> +/**
> + * \brief Centre a rectangle of this size within another rectangular region,
> + * with optional offsets
> + * \param[in] region The rectangular region relative to which the returned
> + * rectangle can be position
> + * \param[in] offsetX The X offset of the mid-point of the returned rectangle
> + * relative to the mid-point of the region
> + * \param[in] offsetY The Y offset of the mid-point of the returned rectangle
> + * relative to the mid-point of the region
> + *
> + * A Rectangle of this object's size is positioned within the Rectangle
> + * given by \a region. It is positioned so that its mid-point coincides
> + * with the mid-point of \a region, and is then further offset by the
> + * values \a offsetX and \a offsetY.
> + *
> + * \return A Rectangle with the horizontal and vertical sizes of
> + * this Size instance, centred with offsets within a region
> + */
> +Rectangle Size::centredTo(const Rectangle &region, int offsetX, int offsetY) const
> +{
> +	int x = (region.width - width) / 2 + region.x + offsetX;
> +	int y = (region.height - height) / 2 + region.y + offsetY;
> +
> +	return Rectangle(x, y, width, height);
> +}
> +
> +/**
> + * \brief Scale size up by the given factor
> + * \return The scaled Size
> + */
> +Size operator*(const Size &size, float f)
> +{
> +	return Size(size.width * f, size.height * f);
> +}
> +
> +/**
> + * \brief Scale size down by the given factor
> + * \return The scaled Size
> + */
> +Size operator/(const Size &size, float f)
> +{
> +	return Size(size.width / f, size.height / f);
> +}
> +
>  /**
>   * \brief Compare sizes for equality
>   * \return True if the two sizes are equal, false otherwise
> @@ -365,6 +447,12 @@ bool operator==(const SizeRange &lhs, const SizeRange &rhs)
>   * \param[in] height The height
>   */
>  
> +/**
> + * \fn Rectangle::Rectangle(const Size &size)
> + * \brief Construct a Rectangle with zero offsets and the given \a size
> + * \param[in] size The desired Rectangle size
> + */
> +
>  /**
>   * \var Rectangle::x
>   * \brief The horizontal coordinate of the rectangle's top-left corner
> @@ -404,6 +492,47 @@ const std::string Rectangle::toString() const
>  	return ss.str();
>  }
>  
> +/**
> + * \brief Retrieve the size of this rectangle
> + * \return A Size reporting the Rectangle horizontal and vertical sizes
> + */
> +Size Rectangle::size() const
> +{
> +	return Size(width, height);
> +}
> +
> +/**
> + * \brief Bound a Rectangle so as not to exceeed another Rectangle

s/exceeed/exceed/

> + * \param[in] boundary The limit that the returned Rectangle will not exceed
> + *
> + * The Rectangle is bounded so that it does not exceeed the given \a boundary.

s/exceeed/exceed/

> + * This process involves translating the Rectangle if any of its edges
> + * lie beyond \a boundary, so that those edges then lie along the boundary
> + * instead.
> + *
> + * If either width or height are larger than \a bounary, then the returned

s/bounary/boundary/

> + * Rectangle is clipped to be no larger. But other than this, the
> + * Rectangle is not clipped or reduced in size, merely translated.
> + *
> + * We note that this is not a conventional Rectangle intersection function.
> + *
> + * \return A Rectangle that does not extend beyond a boundary Rectangle
> + */
> +Rectangle Rectangle::boundedTo(const Rectangle &boundary) const
> +{
> +	Rectangle result(*this);
> +
> +	result.width = std::min(result.width, boundary.width);
> +	result.x = std::clamp<int>(result.x, boundary.x,
> +				   boundary.x + boundary.width - result.width);
> +
> +	result.height = std::min(result.height, boundary.height);
> +	result.y = std::clamp<int>(result.y, boundary.y,
> +				   boundary.y + boundary.height - result.height);
> +
> +	return result;
> +}
> +
>  /**
>   * \brief Compare rectangles for equality
>   * \return True if the two rectangles are equal, false otherwise
> 

-- 
Regards
--
Kieran