[libcamera-devel] [PATCH] ipa: rpi: alsc: Do not allow zero colour ratio statistics

[David Plowman]

The algorithm computes R/G and B/G colour ratio statistics which we
should not allow to go to zero because there is clearly no gain you
could apply to R or B to equalise them. Instead flag such regions as
having "insufficient data" in the normal manner.

Signed-off-by: David Plowman
---
 src/ipa/rpi/controller/rpi/alsc.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/ipa/rpi/controller/rpi/alsc.cpp b/src/ipa/rpi/controller/rpi/alsc.cpp
index b7413611..8a205c60 100644
--- a/src/ipa/rpi/controller/rpi/alsc.cpp
+++ b/src/ipa/rpi/controller/rpi/alsc.cpp
@@ -548,7 +548,9 @@ static void calculateCrCb(const RgbyRegions &awbRegion, Array2D<double> &cr,
 	for (unsigned int i = 0; i < cr.size(); i++) {
 		auto s = awbRegion.get(i);
 
-		if (s.counted <= minCount || s.val.gSum / s.counted <= minG) {
+		/* Do not return unreliable, or zero, colour ratio statistics. */
+		if (s.counted <= minCount || s.val.gSum / s.counted <= minG ||
+		    s.val.rSum / s.counted <= minG || s.val.bSum / s.counted <= minG) {
 			cr[i] = cb[i] = InsufficientData;
 			continue;
 		}
-- 
2.30.2