[libcamera-devel] [PATCH v11 7/8] libcamera: Add validateColorSpaces to CameraConfiguration class

[David Plowman]

This function forces raw streams to have the "raw" color space, and
also optionally makes all non-raw output streams to share the same
color space as some platforms may require this.

When sharing color spaces we take the shared value to be the one from
the largest of these streams. This choice is ultimately arbitrary, but
can be appropriate if smaller output streams are used for image
analysis rather than human consumption, when the precise colours may
be less important.

Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
---
 include/libcamera/camera.h | 10 +++++
 src/libcamera/camera.cpp   | 80 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 90 insertions(+)

diff --git a/include/libcamera/camera.h b/include/libcamera/camera.h
index a7759ccb..5bb06584 100644
--- a/include/libcamera/camera.h
+++ b/include/libcamera/camera.h
@@ -13,6 +13,7 @@
 #include <string>
 
 #include <libcamera/base/class.h>
+#include <libcamera/base/flags.h>
 #include <libcamera/base/object.h>
 #include <libcamera/base/signal.h>
 
@@ -69,6 +70,15 @@ public:
 protected:
 	CameraConfiguration();
 
+	enum class ColorSpaceFlag {
+		None,
+		StreamsShareColorSpace,
+	};
+
+	using ColorSpaceFlags = Flags<ColorSpaceFlag>;
+
+	Status validateColorSpaces(ColorSpaceFlags flags = ColorSpaceFlag::None);
+
 	std::vector<StreamConfiguration> config_;
 };
 
diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp
index 400a7cf0..5f8533e8 100644
--- a/src/libcamera/camera.cpp
+++ b/src/libcamera/camera.cpp
@@ -14,12 +14,14 @@
 #include <libcamera/base/log.h>
 #include <libcamera/base/thread.h>
 
+#include <libcamera/color_space.h>
 #include <libcamera/framebuffer_allocator.h>
 #include <libcamera/request.h>
 #include <libcamera/stream.h>
 
 #include "libcamera/internal/camera.h"
 #include "libcamera/internal/camera_controls.h"
+#include "libcamera/internal/formats.h"
 #include "libcamera/internal/pipeline_handler.h"
 
 /**
@@ -314,6 +316,84 @@ std::size_t CameraConfiguration::size() const
 	return config_.size();
 }
 
+namespace {
+
+bool isRaw(const PixelFormat &pixFmt)
+{
+	const PixelFormatInfo &info = PixelFormatInfo::info(pixFmt);
+	return info.isValid() &&
+	       info.colourEncoding == PixelFormatInfo::ColourEncodingRAW;
+}
+
+} /* namespace */
+
+/**
+ * \enum CameraConfiguration::ColorSpaceFlag
+ * \brief Specify the behaviour of validateColorSpaces
+ * \var CameraConfiguration::ColorSpaceFlag::None
+ * \brief No extra validation of color spaces is required
+ * \var CameraConfiguration::ColorSpaceFlag::StreamsShareColorSpace
+ * \brief Non-raw output streams must share the same color space
+ */
+
+/**
+ * \typedef CameraConfiguration::ColorSpaceFlags
+ * \brief A bitwise combination of ColorSpaceFlag values
+ */
+
+/**
+ * \brief Check the color spaces requested for each stream
+ * \param[in] flags Flags to control the behaviour of this function
+ *
+ * This function performs certain consistency checks on the color spaces of
+ * the streams and may adjust them so that:
+ *
+ * - Any raw streams have the Raw color space
+ * - If the StreamsShareColorSpace flag is set, all output streams are forced
+ * to share the same color space (this may be a constraint on some platforms).
+ *
+ * It is optional for a pipeline handler to use this function.
+ *
+ * \return A CameraConfiguration::Status value that describes the validation
+ * status.
+ * \retval CameraConfigutation::Adjusted The configuration has been adjusted
+ * and is now valid. The color space of some or all of the streams may bave
+ * benn changed. The caller shall check the color spaces carefully.
+ * \retval CameraConfiguration::Valid The configuration was already valid and
+ * hasn't been adjusted.
+ */
+CameraConfiguration::Status CameraConfiguration::validateColorSpaces(ColorSpaceFlags flags)
+{
+	Status status = Valid;
+
+	/*
+	 * Set all raw streams to the Raw color space, and make a note of the largest
+	 * non-raw stream with a defined color space (if there is one).
+	 */
+	int index = -1;
+	for (auto [i, cfg] : utils::enumerate(config_)) {
+		if (isRaw(cfg.pixelFormat) && cfg.colorSpace != ColorSpace::Raw) {
+			cfg.colorSpace = ColorSpace::Raw;
+			status = Adjusted;
+		} else if (cfg.colorSpace && (index == -1 || cfg.size > config_[i].size))
+			index = i;
+	}
+
+	if (index < 0 || !(flags & ColorSpaceFlag::StreamsShareColorSpace))
+		return status;
+
+	/* Make all output color spaces the same, if requested. */
+	for (auto &cfg : config_) {
+		if (!isRaw(cfg.pixelFormat) &&
+		    cfg.colorSpace != config_[index].colorSpace) {
+			cfg.colorSpace = config_[index].colorSpace;
+			status = Adjusted;
+		}
+	}
+
+	return status;
+}
+
 /**
  * \var CameraConfiguration::transform
  * \brief User-specified transform to be applied to the image
-- 
2.30.2