libcamera: ipa: raspberrypi: Add sharpness strength control

The sharpness control is, loosely speaking, a gain applied to
the amount of sharpening added to an image. We also report the
sharpness setting used back to the caller in metadata.

Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 23 insertions, 5 deletions

diff --git a/src/ipa/raspberrypi/controller/rpi/sharpen.cpp b/src/ipa/raspberrypi/controller/rpi/sharpen.cpp
index 4c2fdb3e..2b701db5 100644
--- a/src/ipa/raspberrypi/controller/rpi/sharpen.cpp
+++ b/src/ipa/raspberrypi/controller/rpi/sharpen.cpp
@@ -17,7 +17,7 @@ using namespace RPi;
 #define NAME "rpi.sharpen"
 
 Sharpen::Sharpen(Controller *controller)
-	: Algorithm(controller)
+	: SharpenAlgorithm(controller), user_strength_(1.0)
 {
 }
 
@@ -42,14 +42,32 @@ void Sharpen::Read(boost::property_tree::ptree const &params)
 	limit_ = params.get<double>("limit", 1.0);
 }
 
+void Sharpen::SetStrength(double strength)
+{
+	// Note that this method is how an application sets the overall
+	// sharpening "strength". We call this the "user strength" field
+	// as there already is a strength_ field - being an internal gain
+	// parameter that gets passed to the ISP control code. Negative
+	// values are not allowed - coerce them to zero (no sharpening).
+	user_strength_ = std::max(0.0, strength);
+}
+
 void Sharpen::Prepare(Metadata *image_metadata)
 {
+	// The user_strength_ affects the algorithm's internal gain directly, but
+	// we adjust the limit and threshold less aggressively. Using a sqrt
+	// function is an arbitrary but gentle way of accomplishing this.
+	double user_strength_sqrt = sqrt(user_strength_);
 	struct SharpenStatus status;
 	// Binned modes seem to need the sharpening toned down with this
-	// pipeline.
-	status.threshold = threshold_ * mode_factor_;
-	status.strength = strength_ / mode_factor_;
-	status.limit = limit_ / mode_factor_;
+	// pipeline, thus we use the mode_factor here. Also avoid
+	// divide-by-zero with the user_strength_sqrt.
+	status.threshold = threshold_ * mode_factor_ /
+			   std::max(0.01, user_strength_sqrt);
+	status.strength = strength_ / mode_factor_ * user_strength_;
+	status.limit = limit_ / mode_factor_ * user_strength_sqrt;
+	// Finally, report any application-supplied parameters that were used.
+	status.user_strength = user_strength_;
 	image_metadata->Set("sharpen.status", status);
 }