[PATCH v6 15/18] libcamera: debayer_cpu: Add BGR888 output support

[Milan Zamazal]

From: Hans de Goede <hdegoede at redhat.com>

BGR888 is RGB888 with the red and blue pixels swapped, adjust
the debayering to swap the red and blue pixels in the bayer pattern
to add support for writing formats::BGR888.

Tested-by: Bryan O'Donoghue <bryan.odonoghue at linaro.org> # sc8280xp Lenovo x13s
Tested-by: Pavel Machek <pavel at ucw.cz>
Reviewed-by: Milan Zamazal <mzamazal at redhat.com>
Signed-off-by: Hans de Goede <hdegoede at redhat.com>
Reviewed-by: Stefan Klug <stefan.klug at ideasonboard.com>
---
 src/libcamera/software_isp/debayer_cpu.cpp | 42 +++++++++++++++++++---
 src/libcamera/software_isp/debayer_cpu.h   |  1 +
 2 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/src/libcamera/software_isp/debayer_cpu.cpp b/src/libcamera/software_isp/debayer_cpu.cpp
index eb1c2718..a1692693 100644
--- a/src/libcamera/software_isp/debayer_cpu.cpp
+++ b/src/libcamera/software_isp/debayer_cpu.cpp
@@ -268,7 +268,7 @@ int DebayerCpu::getInputConfig(PixelFormat inputFormat, DebayerInputConfig &conf
 		config.bpp = (bayerFormat.bitDepth + 7) & ~7;
 		config.patternSize.width = 2;
 		config.patternSize.height = 2;
-		config.outputFormats = std::vector<PixelFormat>({ formats::RGB888 });
+		config.outputFormats = std::vector<PixelFormat>({ formats::RGB888, formats::BGR888 });
 		return 0;
 	}
 
@@ -278,7 +278,7 @@ int DebayerCpu::getInputConfig(PixelFormat inputFormat, DebayerInputConfig &conf
 		config.bpp = 10;
 		config.patternSize.width = 4; /* 5 bytes per *4* pixels */
 		config.patternSize.height = 2;
-		config.outputFormats = std::vector<PixelFormat>({ formats::RGB888 });
+		config.outputFormats = std::vector<PixelFormat>({ formats::RGB888, formats::BGR888 });
 		return 0;
 	}
 
@@ -289,7 +289,7 @@ int DebayerCpu::getInputConfig(PixelFormat inputFormat, DebayerInputConfig &conf
 
 int DebayerCpu::getOutputConfig(PixelFormat outputFormat, DebayerOutputConfig &config)
 {
-	if (outputFormat == formats::RGB888) {
+	if (outputFormat == formats::RGB888 || outputFormat == formats::BGR888) {
 		config.bpp = 24;
 		return 0;
 	}
@@ -325,13 +325,41 @@ int DebayerCpu::setupStandardBayerOrder(BayerFormat::Order order)
 	return 0;
 }
 
-/* TODO: this ignores outputFormat since there is only 1 supported outputFormat for now */
-int DebayerCpu::setDebayerFunctions(PixelFormat inputFormat, [[maybe_unused]] PixelFormat outputFormat)
+int DebayerCpu::setDebayerFunctions(PixelFormat inputFormat, PixelFormat outputFormat)
 {
 	BayerFormat bayerFormat =
 		BayerFormat::fromPixelFormat(inputFormat);
 
 	xShift_ = 0;
+	swapRedBlueGains_ = false;
+
+	switch (outputFormat) {
+	case formats::RGB888:
+		break;
+	case formats::BGR888:
+		/* Swap R and B in bayer order to generate BGR888 instead of RGB888 */
+		swapRedBlueGains_ = true;
+
+		switch (bayerFormat.order) {
+		case BayerFormat::BGGR:
+			bayerFormat.order = BayerFormat::RGGB;
+			break;
+		case BayerFormat::GBRG:
+			bayerFormat.order = BayerFormat::GRBG;
+			break;
+		case BayerFormat::GRBG:
+			bayerFormat.order = BayerFormat::GBRG;
+			break;
+		case BayerFormat::RGGB:
+			bayerFormat.order = BayerFormat::BGGR;
+			break;
+		default:
+			goto invalid_fmt;
+		}
+		break;
+	default:
+		goto invalid_fmt;
+	}
 
 	if ((bayerFormat.bitDepth == 8 || bayerFormat.bitDepth == 10 || bayerFormat.bitDepth == 12) &&
 	    bayerFormat.packing == BayerFormat::Packing::None &&
@@ -378,6 +406,7 @@ int DebayerCpu::setDebayerFunctions(PixelFormat inputFormat, [[maybe_unused]] Pi
 		}
 	}
 
+invalid_fmt:
 	LOG(Debayer, Error) << "Unsupported input output format combination";
 	return -EINVAL;
 }
@@ -661,6 +690,9 @@ void DebayerCpu::process(FrameBuffer *input, FrameBuffer *output, DebayerParams
 		gamma_correction_ = params.gamma;
 	}
 
+	if (swapRedBlueGains_)
+		std::swap(params.gainR, params.gainB);
+
 	for (unsigned int i = 0; i < kRGBLookupSize; i++) {
 		constexpr unsigned int div =
 			kRGBLookupSize * DebayerParams::kGain10 / kGammaLookupSize;
diff --git a/src/libcamera/software_isp/debayer_cpu.h b/src/libcamera/software_isp/debayer_cpu.h
index fd1fa180..5f44fc65 100644
--- a/src/libcamera/software_isp/debayer_cpu.h
+++ b/src/libcamera/software_isp/debayer_cpu.h
@@ -145,6 +145,7 @@ private:
 	unsigned int lineBufferIndex_;
 	unsigned int xShift_; /* Offset of 0/1 applied to window_.x */
 	bool enableInputMemcpy_;
+	bool swapRedBlueGains_;
 	float gamma_correction_;
 	unsigned int measuredFrames_;
 	int64_t frameProcessTime_;
-- 
2.42.0