libcamera: geometry: Add Rectangle::transformedBetween()

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@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>

include/libcamera/geometry.h

@@ -299,6 +299,9 @@ public:
 	__nodiscard Rectangle scaledBy(const Size &numerator,
 				       const Size &denominator) const;
 	__nodiscard Rectangle translatedBy(const Point &point) const;
+
+	Rectangle transformedBetween(const Rectangle &source,
+				     const Rectangle &target) const;
 };
 
 bool operator==(const Rectangle &lhs, const Rectangle &rhs);