[v2,2/5] libcamera: software_isp: Honor black level in AWB
diff mbox series

Message ID 20240430173430.200392-3-mzamazal@redhat.com
State New
Headers show
Series
  • Software ISP levels cleanup
Related show

Commit Message

Milan Zamazal April 30, 2024, 5:34 p.m. UTC
The white balance computation didn't consider black level.  This is
wrong because then the computed ratios are off when they are computed
from the whole brightness range rather than the sensor range.

This patch adjusts white balance computation for the black level.  There
is no need to change white balance application in debayering as this is
already applied after black level correction.

Exposure computation already subtracts black level, no changes are
needed there.

Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
---
 src/ipa/simple/soft_simple.cpp | 36 ++++++++++++++++++++++------------
 1 file changed, 23 insertions(+), 13 deletions(-)

Comments

Andrei Konovalov May 22, 2024, 9:45 a.m. UTC | #1
Hi Milan,

Thank you for the patch!

Reviewed-by: Andrei Konovalov <andrey.konovalov.ynk@gmail.com>

On 30.04.2024 20:34, Milan Zamazal wrote:
> The white balance computation didn't consider black level.  This is
> wrong because then the computed ratios are off when they are computed
> from the whole brightness range rather than the sensor range.
> 
> This patch adjusts white balance computation for the black level.  There
> is no need to change white balance application in debayering as this is
> already applied after black level correction.
> 
> Exposure computation already subtracts black level, no changes are
> needed there.
> 
> Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
> ---
>   src/ipa/simple/soft_simple.cpp | 36 ++++++++++++++++++++++------------
>   1 file changed, 23 insertions(+), 13 deletions(-)
> 
> diff --git a/src/ipa/simple/soft_simple.cpp b/src/ipa/simple/soft_simple.cpp
> index b9fb58b5..f595abc2 100644
> --- a/src/ipa/simple/soft_simple.cpp
> +++ b/src/ipa/simple/soft_simple.cpp
> @@ -5,6 +5,8 @@
>    * soft_simple.cpp - Simple Software Image Processing Algorithm module
>    */
>   
> +#include <numeric>
> +#include <stdint.h>
>   #include <sys/mman.h>
>   
>   #include <linux/v4l2-controls.h>
> @@ -240,28 +242,36 @@ void IPASoftSimple::stop()
>   
>   void IPASoftSimple::processStats(const ControlList &sensorControls)
>   {
> +	SwIspStats::Histogram histogram = stats_->yHistogram;
> +	if (ignoreUpdates_ > 0)
> +		blackLevel_.update(histogram);
> +	const uint8_t blackLevel = blackLevel_.get();
> +	params_->blackLevel = blackLevel;
> +
>   	/*
>   	 * Calculate red and blue gains for AWB.
>   	 * Clamp max gain at 4.0, this also avoids 0 division.
> +	 * Black level must be subtracted to get the correct AWB ratios,
> +	 * from the sensor range.
>   	 */
> -	if (stats_->sumR_ <= stats_->sumG_ / 4)
> -		params_->gainR = 1024;
> -	else
> -		params_->gainR = 256 * stats_->sumG_ / stats_->sumR_;
> -
> -	if (stats_->sumB_ <= stats_->sumG_ / 4)
> -		params_->gainB = 1024;
> -	else
> -		params_->gainB = 256 * stats_->sumG_ / stats_->sumB_;
> +	const uint64_t nPixels = std::accumulate(
> +		histogram.begin(), histogram.end(), 0);
> +	auto subtractBlackLevel = [blackLevel, nPixels](
> +					  uint64_t sum, uint64_t div)
> +		-> uint64_t {
> +		return sum - blackLevel * nPixels / div;
> +	};
> +	const uint64_t sumR = subtractBlackLevel(stats_->sumR_, 4);
> +	const uint64_t sumG = subtractBlackLevel(stats_->sumG_, 2);
> +	const uint64_t sumB = subtractBlackLevel(stats_->sumB_, 4);
> +
> +	params_->gainR = sumR <= sumG / 4 ? 1024 : 256 * sumG / sumR;
> +	params_->gainB = sumB <= sumG / 4 ? 1024 : 256 * sumG / sumB;
>   
>   	/* Green gain and gamma values are fixed */
>   	params_->gainG = 256;
>   	params_->gamma = 0.5;
>   
> -	if (ignoreUpdates_ > 0)
> -		blackLevel_.update(stats_->yHistogram);
> -	params_->blackLevel = blackLevel_.get();
> -
>   	setIspParams.emit();
>   
>   	/* \todo Switch to the libipa/algorithm.h API someday. */

Patch
diff mbox series

diff --git a/src/ipa/simple/soft_simple.cpp b/src/ipa/simple/soft_simple.cpp
index b9fb58b5..f595abc2 100644
--- a/src/ipa/simple/soft_simple.cpp
+++ b/src/ipa/simple/soft_simple.cpp
@@ -5,6 +5,8 @@ 
  * soft_simple.cpp - Simple Software Image Processing Algorithm module
  */
 
+#include <numeric>
+#include <stdint.h>
 #include <sys/mman.h>
 
 #include <linux/v4l2-controls.h>
@@ -240,28 +242,36 @@  void IPASoftSimple::stop()
 
 void IPASoftSimple::processStats(const ControlList &sensorControls)
 {
+	SwIspStats::Histogram histogram = stats_->yHistogram;
+	if (ignoreUpdates_ > 0)
+		blackLevel_.update(histogram);
+	const uint8_t blackLevel = blackLevel_.get();
+	params_->blackLevel = blackLevel;
+
 	/*
 	 * Calculate red and blue gains for AWB.
 	 * Clamp max gain at 4.0, this also avoids 0 division.
+	 * Black level must be subtracted to get the correct AWB ratios,
+	 * from the sensor range.
 	 */
-	if (stats_->sumR_ <= stats_->sumG_ / 4)
-		params_->gainR = 1024;
-	else
-		params_->gainR = 256 * stats_->sumG_ / stats_->sumR_;
-
-	if (stats_->sumB_ <= stats_->sumG_ / 4)
-		params_->gainB = 1024;
-	else
-		params_->gainB = 256 * stats_->sumG_ / stats_->sumB_;
+	const uint64_t nPixels = std::accumulate(
+		histogram.begin(), histogram.end(), 0);
+	auto subtractBlackLevel = [blackLevel, nPixels](
+					  uint64_t sum, uint64_t div)
+		-> uint64_t {
+		return sum - blackLevel * nPixels / div;
+	};
+	const uint64_t sumR = subtractBlackLevel(stats_->sumR_, 4);
+	const uint64_t sumG = subtractBlackLevel(stats_->sumG_, 2);
+	const uint64_t sumB = subtractBlackLevel(stats_->sumB_, 4);
+
+	params_->gainR = sumR <= sumG / 4 ? 1024 : 256 * sumG / sumR;
+	params_->gainB = sumB <= sumG / 4 ? 1024 : 256 * sumG / sumB;
 
 	/* Green gain and gamma values are fixed */
 	params_->gainG = 256;
 	params_->gamma = 0.5;
 
-	if (ignoreUpdates_ > 0)
-		blackLevel_.update(stats_->yHistogram);
-	params_->blackLevel = blackLevel_.get();
-
 	setIspParams.emit();
 
 	/* \todo Switch to the libipa/algorithm.h API someday. */