[libcamera-devel] [PATCH v2 1/4] libcamera: Add the fromV4L2PixelFormat function

[Sebastian Fricke]

Add a static member function to get the corresponding Bayer-format
from a given V4L2PixelFormat.
Replace an existing method to instantiate an object from a matching
V4l2PixelFormat, to not duplicate the code.
The motivation behind this patch is to align the overall structure
of the BayerFormat class with other parts of the code base, such as
the V4L2PixelFormat class.

Remove the v4l2ToBayer mapping table and use the bayerToV4l2 mapping
table by searching for a mapped element to get the corresponding key.
The downside of this approach is a slightly worse time complexity, but
the upside is a smaller codebase and lower memory consumption. As the
function is probably not used very frequently, I tend to favor the
mentioned upsides.

Signed-off-by: Sebastian Fricke <sebastian.fricke.linux at gmail.com>
---
 include/libcamera/internal/bayer_format.h |  1 +
 src/libcamera/bayer_format.cpp            | 63 +++++++----------------
 2 files changed, 19 insertions(+), 45 deletions(-)

diff --git a/include/libcamera/internal/bayer_format.h b/include/libcamera/internal/bayer_format.h
index 4280b76b..8efe1382 100644
--- a/include/libcamera/internal/bayer_format.h
+++ b/include/libcamera/internal/bayer_format.h
@@ -48,6 +48,7 @@ public:
 	std::string toString() const;
 
 	V4L2PixelFormat toV4L2PixelFormat() const;
+	static BayerFormat fromV4L2PixelFormat(V4L2PixelFormat v4l2Format);
 	BayerFormat transform(Transform t) const;
 
 	Order order;
diff --git a/src/libcamera/bayer_format.cpp b/src/libcamera/bayer_format.cpp
index c42792ff..26065b66 100644
--- a/src/libcamera/bayer_format.cpp
+++ b/src/libcamera/bayer_format.cpp
@@ -7,6 +7,7 @@
 
 #include "libcamera/internal/bayer_format.h"
 
+#include <algorithm>
 #include <map>
 
 #include <libcamera/transform.h>
@@ -57,37 +58,6 @@ namespace libcamera {
 
 namespace {
 
-const std::map<V4L2PixelFormat, BayerFormat> v4l2ToBayer{
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SBGGR8), { BayerFormat::BGGR, 8, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SGBRG8), { BayerFormat::GBRG, 8, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SGRBG8), { BayerFormat::GRBG, 8, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SRGGB8), { BayerFormat::RGGB, 8, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SBGGR10), { BayerFormat::BGGR, 10, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SGBRG10), { BayerFormat::GBRG, 10, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SGRBG10), { BayerFormat::GRBG, 10, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SRGGB10), { BayerFormat::RGGB, 10, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SBGGR10P), { BayerFormat::BGGR, 10, BayerFormat::CSI2Packed } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SGBRG10P), { BayerFormat::GBRG, 10, BayerFormat::CSI2Packed } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SGRBG10P), { BayerFormat::GRBG, 10, BayerFormat::CSI2Packed } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SRGGB10P), { BayerFormat::RGGB, 10, BayerFormat::CSI2Packed } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_IPU3_SBGGR10), { BayerFormat::BGGR, 10, BayerFormat::IPU3Packed } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_IPU3_SGBRG10), { BayerFormat::GBRG, 10, BayerFormat::IPU3Packed } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_IPU3_SGRBG10), { BayerFormat::GRBG, 10, BayerFormat::IPU3Packed } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_IPU3_SRGGB10), { BayerFormat::RGGB, 10, BayerFormat::IPU3Packed } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SBGGR12), { BayerFormat::BGGR, 12, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SGBRG12), { BayerFormat::GBRG, 12, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SGRBG12), { BayerFormat::GRBG, 12, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SRGGB12), { BayerFormat::RGGB, 12, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SBGGR12P), { BayerFormat::BGGR, 12, BayerFormat::CSI2Packed } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SGBRG12P), { BayerFormat::GBRG, 12, BayerFormat::CSI2Packed } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SGRBG12P), { BayerFormat::GRBG, 12, BayerFormat::CSI2Packed } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SRGGB12P), { BayerFormat::RGGB, 12, BayerFormat::CSI2Packed } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SBGGR16), { BayerFormat::BGGR, 16, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SGBRG16), { BayerFormat::GBRG, 16, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SGRBG16), { BayerFormat::GRBG, 16, BayerFormat::None } },
-	{ V4L2PixelFormat(V4L2_PIX_FMT_SRGGB16), { BayerFormat::RGGB, 16, BayerFormat::None } },
-};
-
 /* Define a slightly arbitrary ordering so that we can use a std::map. */
 struct BayerFormatComparator {
 	constexpr bool operator()(const BayerFormat &lhs, const BayerFormat &rhs) const
@@ -155,20 +125,6 @@ const std::map<BayerFormat, V4L2PixelFormat, BayerFormatComparator> bayerToV4l2{
  * \param[in] p The type of packing applied to the pixel values
  */
 
-/**
- * \brief Construct a BayerFormat from a V4L2PixelFormat
- * \param[in] v4l2Format The raw format to convert into a BayerFormat
- */
-BayerFormat::BayerFormat(V4L2PixelFormat v4l2Format)
-	: order(BGGR), packing(None)
-{
-	const auto it = v4l2ToBayer.find(v4l2Format);
-	if (it == v4l2ToBayer.end())
-		bitDepth = 0;
-	else
-		*this = it->second;
-}
-
 /**
  * \fn BayerFormat::isValid()
  * \brief Return whether a BayerFormat is valid
@@ -217,6 +173,23 @@ V4L2PixelFormat BayerFormat::toV4L2PixelFormat() const
 	return V4L2PixelFormat();
 }
 
+/**
+ * \brief Convert \a v4l2Format into the corresponding BayerFormat
+ * \param[in] v4l2Format The raw format to convert into a BayerFormat
+ * \return The BayerFormat corresponding to \a v4l2Format
+ */
+BayerFormat BayerFormat::fromV4L2PixelFormat(V4L2PixelFormat v4l2Format)
+{
+	auto it = std::find_if(
+		bayerToV4l2.begin(),
+		bayerToV4l2.end(),
+		[v4l2Format](const auto &i) { return i.second == v4l2Format; });
+	if (it != bayerToV4l2.end())
+		return it->first;
+
+	return BayerFormat();
+}
+
 /**
  * \brief Apply a transform to this BayerFormat
  * \param[in] t The transform to apply
-- 
2.25.1