[libcamera-devel] [PATCH v2 5/5] libcamera: ipa: raspberrypi: ALSC: Handle user transform

[David Plowman]

Update ALSC (Auto Lens Shading Correction) to handle correctly the
user transform now passed in the camera mode.

The user transform is applied directly in the sensor so the image
statistics already incorporate it, and the adaptive algorithm is
entirely agnostic towards it, so all we have to do is flip the
calibrated tables to match. (These tables will have been calibrated
without the user transform.)
---
 src/ipa/raspberrypi/controller/rpi/alsc.cpp | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/ipa/raspberrypi/controller/rpi/alsc.cpp b/src/ipa/raspberrypi/controller/rpi/alsc.cpp
index 9df713a..fdeda21 100644
--- a/src/ipa/raspberrypi/controller/rpi/alsc.cpp
+++ b/src/ipa/raspberrypi/controller/rpi/alsc.cpp
@@ -184,7 +184,10 @@ void Alsc::waitForAysncThread()
 
 static bool compare_modes(CameraMode const &cm0, CameraMode const &cm1)
 {
-	// Return true if the modes crop from the sensor significantly differently.
+	// Return true if the modes crop from the sensor significantly differently,
+	// or if the user transform has changed.
+	if (cm0.transform != cm1.transform)
+		return true;
 	int left_diff = abs(cm0.crop_x - cm1.crop_x);
 	int top_diff = abs(cm0.crop_y - cm1.crop_y);
 	int right_diff = fabs(cm0.crop_x + cm0.scale_x * cm0.width -
@@ -429,6 +432,10 @@ void resample_cal_table(double const cal_table_in[XY],
 		xf[i] = x - x_lo[i];
 		x_hi[i] = std::min(x_lo[i] + 1, X - 1);
 		x_lo[i] = std::max(x_lo[i], 0);
+		if (!!(camera_mode.transform & libcamera::Transform::HFlip)) {
+			x_lo[i] = X - 1 - x_lo[i];
+			x_hi[i] = X - 1 - x_hi[i];
+		}
 	}
 	// Now march over the output table generating the new values.
 	double scale_y = camera_mode.sensor_height /
@@ -441,6 +448,10 @@ void resample_cal_table(double const cal_table_in[XY],
 		double yf = y - y_lo;
 		int y_hi = std::min(y_lo + 1, Y - 1);
 		y_lo = std::max(y_lo, 0);
+		if (!!(camera_mode.transform & libcamera::Transform::VFlip)) {
+			y_lo = Y - 1 - y_lo;
+			y_hi = Y - 1 - y_hi;
+		}
 		double const *row_above = cal_table_in + X * y_lo;
 		double const *row_below = cal_table_in + X * y_hi;
 		for (int i = 0; i < X; i++) {
-- 
2.20.1