libcamera: geometry: Add Size members to grown or shrink by a margin

Add four new member functions to the Size class (two in-place and two
const) to grow and shrink a Size by given margins.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

include/libcamera/geometry.h

@@ -94,6 +94,20 @@ public:
 		return *this;
 	}
 
+	Size &growBy(const Size &margins)
+	{
+		width += margins.width;
+		height += margins.height;
+		return *this;
+	}
+
+	Size &shrinkBy(const Size &margins)
+	{
+		width = width > margins.width ? width - margins.width : 0;
+		height = height > margins.height ? height - margins.height : 0;
+		return *this;
+	}
+
 	__nodiscard constexpr Size alignedDownTo(unsigned int hAlignment,
 						 unsigned int vAlignment) const
 	{
@@ -128,6 +142,22 @@ public:
 		};
 	}
 
+	__nodiscard constexpr Size grownBy(const Size &margins) const
+	{
+		return {
+			width + margins.width,
+			height + margins.height
+		};
+	}
+
+	__nodiscard constexpr Size shrunkBy(const Size &margins) const
+	{
+		return {
+			width > margins.width ? width - margins.width : 0,
+			height > margins.height ? height - margins.height : 0
+		};
+	}
+
 	__nodiscard Size boundedToAspectRatio(const Size &ratio) const;
 	__nodiscard Size expandedToAspectRatio(const Size &ratio) const;
 

src/libcamera/geometry.cpp

@@ -173,6 +173,28 @@ const std::string Size::toString() const
  * \return A reference to this object
  */
 
+/**
+ * \fn Size::growBy(const Size &margins)
+ * \brief Grow the size by \a margins in place
+ * \param[in] margins The margins to add to the size
+ *
+ * This function adds the width and height of the \a margin size to this size.
+ *
+ * \return A reference to this object
+ */
+
+/**
+ * \fn Size::shrinkBy(const Size &margins)
+ * \brief Shrink the size by \a margins in place
+ * \param[in] margins The margins to subtract to the size
+ *
+ * This function subtracts the width and height of the \a margin size from this
+ * size. If the width or height of the size are smaller than those of \a
+ * margins, the result is clamped to 0.
+ *
+ * \return A reference to this object
+ */
+
 /**
  * \fn Size::alignedDownTo(unsigned int hAlignment, unsigned int vAlignment)
  * \brief Align the size down horizontally and vertically
@@ -209,6 +231,26 @@ const std::string Size::toString() const
  * height of this size and the \a expand size
  */
 
+/**
+ * \fn Size::grownBy(const Size &margins)
+ * \brief Grow the size by \a margins
+ * \param[in] margins The margins to add to the size
+ * \return A Size whose width and height are the sum of the width and height of
+ * this size and the \a margins size
+ */
+
+/**
+ * \fn Size::shrunkBy(const Size &margins)
+ * \brief Shrink the size by \a margins
+ * \param[in] margins The margins to subtract to the size
+ *
+ * If the width or height of the size are smaller than those of \a margins, the
+ * resulting size has its width or height clamped to 0.
+ *
+ * \return A Size whose width and height are the difference of the width and
+ * height of this size and the \a margins size, clamped to 0
+ */
+
 /**
  * \brief Bound the size down to match the aspect ratio given by \a ratio
  * \param[in] ratio The size whose aspect ratio must be matched

test/geometry.cpp

@@ -104,7 +104,10 @@ protected:
 			return TestFail;
 		}
 
-		/* Test alignDownTo(), alignUpTo(), boundTo() and expandTo() */
+		/*
+		 * Test alignDownTo(), alignUpTo(), boundTo(), expandTo(),
+		 * growBy() and shrinkBy()
+		 */
 		Size s(50, 50);
 
 		s.alignDownTo(16, 16);
@@ -131,14 +134,36 @@ protected:
 			return TestFail;
 		}
 
-		s.alignDownTo(16, 16).alignUpTo(32, 32)
+		s.growBy({ 10, 20 });
-		 .boundTo({ 40, 80 }).expandTo({ 16, 80 });
+		if (s != Size(60, 70)) {
-		if (s != Size(40, 80)) {
+			cout << "Size::growBy() test failed" << endl;
+			return TestFail;
+		}
+
+		s.shrinkBy({ 20, 10 });
+		if (s != Size(40, 60)) {
+			cout << "Size::shrinkBy() test failed" << endl;
+			return TestFail;
+		}
+
+		s.shrinkBy({ 100, 100 });
+		if (s != Size(0, 0)) {
+			cout << "Size::shrinkBy() clamp test failed" << endl;
+			return TestFail;
+		}
+
+		s = Size(50,50).alignDownTo(16, 16).alignUpTo(32, 32)
+		  .boundTo({ 40, 80 }).expandTo({ 16, 80 })
+		  .growBy({ 4, 4 }).shrinkBy({ 10, 20 });
+		if (s != Size(34, 64)) {
 			cout << "Size chained in-place modifiers test failed" << endl;
 			return TestFail;
 		}
 
-		/* Test alignedDownTo(), alignedUpTo(), boundedTo() and expandedTo() */
+		/*
+		 * Test alignedDownTo(), alignedUpTo(), boundedTo(),
+		 * expandedTo(), grownBy() and shrunkBy()
+		 */
 		if (Size(0, 0).alignedDownTo(16, 8) != Size(0, 0) ||
 		    Size(1, 1).alignedDownTo(16, 8) != Size(0, 0) ||
 		    Size(16, 8).alignedDownTo(16, 8) != Size(16, 8)) {
@@ -167,6 +192,19 @@ protected:
 			return TestFail;
 		}
 
+		if (Size(0, 0).grownBy({ 10, 20 }) != Size(10, 20) ||
+		    Size(200, 50).grownBy({ 10, 20 }) != Size(210, 70)) {
+			cout << "Size::grownBy() test failed" << endl;
+			return TestFail;
+		}
+
+		if (Size(200, 50).shrunkBy({ 10, 20 }) != Size(190, 30) ||
+		    Size(200, 50).shrunkBy({ 10, 100 }) != Size(190, 0) ||
+		    Size(200, 50).shrunkBy({ 300, 20 }) != Size(0, 30)) {
+			cout << "Size::shrunkBy() test failed" << endl;
+			return TestFail;
+		}
+
 		/* Aspect ratio tests */
 		if (Size(0, 0).boundedToAspectRatio(Size(4, 3)) != Size(0, 0) ||
 		    Size(1920, 1440).boundedToAspectRatio(Size(16, 9)) != Size(1920, 1080) ||