[libcamera-devel] [PATCH v5 06/23] libcamera: PixelFormatInfo: Add functions stride and frameSize

[Paul Elder]

Add member functions to PixelFormatInfo for calculating stride and frame
size. This will simplify existing code that calculates these things.

Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

---
Changes in v5:
- changed default align parameter for stride() to 1
- added align parameter to frameSize()

Changes in v4:
- add overloaded frameSize() that takes array of strides
- add optional parameter to stride() for byte alignment

Changes in v3:
- rename functions to stride and frameSize, from bytesPerLine and
  imageSize, respectively

Changes in v2:
- make these functions const
- add documentation
- inline DIV_ROUND_UP
---
 include/libcamera/internal/formats.h |  6 +++
 src/libcamera/formats.cpp            | 80 ++++++++++++++++++++++++++++
 2 files changed, 86 insertions(+)

diff --git a/include/libcamera/internal/formats.h b/include/libcamera/internal/formats.h
index 211da4a..cad41ad 100644
--- a/include/libcamera/internal/formats.h
+++ b/include/libcamera/internal/formats.h
@@ -53,6 +53,12 @@ public:
 	static const PixelFormatInfo &info(const PixelFormat &format);
 	static const PixelFormatInfo &info(const V4L2PixelFormat &format);
 
+	unsigned int stride(unsigned int width, unsigned int plane,
+			    unsigned int align = 1) const;
+	unsigned int frameSize(const Size &size, unsigned int align = 1) const;
+	unsigned int frameSize(const Size &size,
+			       const std::array<unsigned int, 3> &strides) const;
+
 	/* \todo Add support for non-contiguous memory planes */
 	const char *name;
 	PixelFormat format;
diff --git a/src/libcamera/formats.cpp b/src/libcamera/formats.cpp
index 6d96055..0f71061 100644
--- a/src/libcamera/formats.cpp
+++ b/src/libcamera/formats.cpp
@@ -732,4 +732,84 @@ const PixelFormatInfo &PixelFormatInfo::info(const V4L2PixelFormat &format)
 	return info->second;
 }
 
+/**
+ * \brief Compute the stride
+ * \param[in] width The width of the line, in pixels
+ * \param[in] plane The index of the plane whose stride is to be computed
+ * \param[in] align The number of bytes to align to (1 for default alignment)
+ * \return The number of bytes necessary to store a line, or 0 if the
+ * PixelFormatInfo instance or the \a plane is not valid
+ */
+unsigned int PixelFormatInfo::stride(unsigned int width, unsigned int plane,
+				     unsigned int align) const
+{
+	if (!isValid()) {
+		LOG(Formats, Warning) << "Invalid pixel format, stride is zero";
+		return 0;
+	}
+
+	if (plane > planes.size() || !planes[plane].bytesPerGroup) {
+		LOG(Formats, Warning) << "Invalid plane index, stride is zero";
+		return 0;
+	}
+
+	/* ceil(width / pixelsPerGroup) * bytesPerGroup */
+	unsigned int stride = (width + pixelsPerGroup - 1) / pixelsPerGroup
+			    * planes[plane].bytesPerGroup;
+
+	/* ceil(stride / align) * align */
+	return (stride + align - 1) / align * align;
+}
+
+/**
+ * \brief Compute the number of bytes necessary to store a frame
+ * \param[in] size The size of the frame, in pixels
+ * \param[in] align The number of bytes to align to (1 for default alignment)
+ * \return The number of bytes necessary to store the frame, or 0 if the
+ * PixelFormatInfo instance is not valid
+ */
+unsigned int PixelFormatInfo::frameSize(const Size &size, unsigned int align) const
+{
+	/* stride * ceil(height / verticalSubSampling) */
+	unsigned int sum = 0;
+	for (unsigned int i = 0; i < 3; i++) {
+		unsigned int vertSubSample = planes[i].verticalSubSampling;
+		if (!vertSubSample)
+			continue;
+		sum += stride(size.width, i, align)
+		     * ((size.height + vertSubSample - 1) / vertSubSample);
+	}
+
+	return sum;
+}
+
+/**
+ * \brief Compute the number of bytes necessary to store a frame
+ * \param[in] size The size of the frame, in pixels
+ * \param[in] strides The strides to use for each plane
+ *
+ * This function is an overloaded version that takes custom strides for each
+ * plane, to be used when the device has custom alignment constraints that
+ * can't be described by just an alignment value.
+ *
+ * \return The number of bytes necessary to store the frame, or 0 if the
+ * PixelFormatInfo instance is not valid
+ */
+unsigned int
+PixelFormatInfo::frameSize(const Size &size,
+			   const std::array<unsigned int, 3> &strides) const
+{
+	/* stride * ceil(height / verticalSubSampling) */
+	unsigned int sum = 0;
+	for (unsigned int i = 0; i < 3; i++) {
+		unsigned int vertSubSample = planes[i].verticalSubSampling;
+		if (!vertSubSample)
+			continue;
+		sum += strides[i]
+		     * ((size.height + vertSubSample - 1) / vertSubSample);
+	}
+
+	return sum;
+}
+
 } /* namespace libcamera */
-- 
2.27.0