[{"id":37969,"web_url":"https://patchwork.libcamera.org/comment/37969/","msgid":"<20260127144731.GA2502390@killaraus>","date":"2026-01-27T14:47:31","subject":"Re: [PATCH] libcamera: simple: Fix black level offsets in AWB","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"On Tue, Jan 27, 2026 at 01:37:28PM +0100, Milan Zamazal wrote:\n> The black level offset subtracted in AWB is wrong. It assumes that the\n> stats contain sums of the individual colour pixels. But they actually\n> contain sums of the colour channels of larger \"superpixels\" consisting\n> of the individual colour pixels. Each of the RGB colour values and the\n> computed luminosity (a histogram entry) are added once to the stats per\n> such a superpixel. This means the offset computed from the black level\n> and the number of pixels should be used as it is, not divided.\n> \n> The patch fixes the subtracted offset. Since it is the same for all the\n> three colours, a SwIspStats helper method returning an RGB instance is\n> introduced. The individual colour variables are still retained in\n> SwIspStats for maximum efficiency when gathering the stats. SwIspStats\n> docstrings are changed to avoid the original confusion.\n> \n> Fixes: 4e13c6f55bd667 (\"Honor black level in AWB\")\n> Signed-off-by: Milan Zamazal \n> ---\n> .../internal/software_isp/swisp_stats.h | 17 +++++++++++++----\n> src/ipa/simple/algorithms/awb.cpp | 10 ++++------\n> 2 files changed, 17 insertions(+), 10 deletions(-)\n> \n> diff --git a/include/libcamera/internal/software_isp/swisp_stats.h b/include/libcamera/internal/software_isp/swisp_stats.h\n> index 3c9860185..f8816209f 100644\n> --- a/include/libcamera/internal/software_isp/swisp_stats.h\n> +++ b/include/libcamera/internal/software_isp/swisp_stats.h\n> @@ -10,6 +10,8 @@\n> #include \n> #include \n> \n> +#include \"libcamera/internal/vector.h\"\n> +\n> namespace libcamera {\n> \n> /**\n> @@ -26,17 +28,24 @@ struct SwIspStats {\n> \t */\n> \tbool valid;\n> \t/**\n> -\t * \\brief Holds the sum of all sampled red pixels\n> +\t * \\brief Holds the sum of red channels of all the sampled pixels\n> \t */\n> \tuint64_t sumR_;\n> \t/**\n> -\t * \\brief Holds the sum of all sampled green pixels\n> +\t * \\brief Holds the sum of green channels of all the sampled pixels\n> \t */\n> \tuint64_t sumG_;\n> \t/**\n> -\t * \\brief Holds the sum of all sampled blue pixels\n> +\t * \\brief Holds the sum of blue channels of all the sampled pixels\n> \t */\n> \tuint64_t sumB_;\n> +\t/**\n> +\t * \\brief Return the sums of colour channels of all the sampled pixels\n> +\t */\n> +\tRGB rgbSum() const\n> +\t{\n> +\t\treturn RGB({ sumR_, sumG_, sumB_ });\n> +\t}\n\nI would have replaced all this with\n\n\tRGB sum_;\n\n(with an appropriate documentation block)\n\n> \t/**\n> \t * \\brief Number of bins in the yHistogram\n> \t */\n> @@ -46,7 +55,7 @@ struct SwIspStats {\n> \t */\n> \tusing Histogram = std::array;\n> \t/**\n> -\t * \\brief A histogram of luminance values\n> +\t * \\brief A histogram of luminance values of all the sampled pixels\n> \t */\n> \tHistogram yHistogram;\n> };\n> diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp\n> index 0080865aa..4c8bfd2de 100644\n> --- a/src/ipa/simple/algorithms/awb.cpp\n> +++ b/src/ipa/simple/algorithms/awb.cpp\n> @@ -1,6 +1,6 @@\n> /* SPDX-License-Identifier: LGPL-2.1-or-later */\n> /*\n> - * Copyright (C) 2024, Red Hat Inc.\n> + * Copyright (C) 2024-2026 Red Hat Inc.\n> *\n> * Auto white balance\n> */\n> @@ -73,9 +73,7 @@ void Awb::process(IPAContext &context,\n> \t\thistogram.begin(), histogram.end(), uint64_t(0));\n> \tconst uint64_t offset = blackLevel * nPixels;\n> \tconst uint64_t minValid = 1;\n> -\tconst uint64_t sumR = stats->sumR_ > offset / 4 ? stats->sumR_ - offset / 4 : minValid;\n> -\tconst uint64_t sumG = stats->sumG_ > offset / 2 ? stats->sumG_ - offset / 2 : minValid;\n> -\tconst uint64_t sumB = stats->sumB_ > offset / 4 ? stats->sumB_ - offset / 4 : minValid;\n> +\tconst RGB sum = (stats->rgbSum() - offset).max(minValid);\n> \n> \t/*\n> \t * Calculate red and blue gains for AWB.\n> @@ -83,9 +81,9 @@ void Awb::process(IPAContext &context,\n> \t */\n> \tauto &gains = context.activeState.awb.gains;\n> \tgains = { {\n> -\t\tsumR <= sumG / 4 ? 4.0f : static_cast(sumG) / sumR,\n> +\t\tsum.r() <= sum.g() / 4 ? 4.0f : static_cast(sum.g()) / sum.r(),\n> \t\t1.0,\n> -\t\tsumB <= sumG / 4 ? 4.0f : static_cast(sumG) / sumB,\n> +\t\tsum.b() <= sum.g() / 4 ? 4.0f : static_cast(sum.g()) / sum.b(),\n> \t} };\n> \n> \tRGB rgbGains{ { 1 / gains.r(), 1 / gains.g(), 1 / gains.b() } };","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 2A45DC3200\n\tfor ;\n\tTue, 27 Jan 2026 14:47:36 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 0CCFB61FCE;\n\tTue, 27 Jan 2026 15:47:35 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 9475961FBF\n\tfor ;\n\tTue, 27 Jan 2026 15:47:33 +0100 (CET)","from pendragon.ideasonboard.com\n\t(2001-14ba-703d-e500--2a1.rev.dnainternet.fi\n\t[IPv6:2001:14ba:703d:e500::2a1])\n\tby perceval.ideasonboard.com (Postfix) with UTF8SMTPSA id 0F4C1177A; \n\tTue, 27 Jan 2026 15:46:57 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"DqLH/Cjh\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1769525217;\n\tbh=FGbpTriy+U2oyO9GyDQDMginuRmpaUFs1FMixQq6LzQ=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=DqLH/CjhWJHSo/2Hivl/hUQfkywgH1TuHfw+BkfUNMOTvo2qezvtBzYFHEXZiTeop\n\tholtVG/UeeD5dzJdEN71KxTkWy82stFxDyU1ThWiDYJ3ep+UPQjWwcW/z8iuSy7jIy\n\tT59IvGChcNevFgsi2KFVe86ZXcITr5wi3gwjiqfU=","Date":"Tue, 27 Jan 2026 16:47:31 +0200","From":"Laurent Pinchart ","To":"Milan Zamazal ","Cc":"libcamera-devel@lists.libcamera.org","Subject":"Re: [PATCH] libcamera: simple: Fix black level offsets in AWB","Message-ID":"<20260127144731.GA2502390@killaraus>","References":"<20260127123728.70513-1-mzamazal@redhat.com>","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"<20260127123728.70513-1-mzamazal@redhat.com>","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":37970,"web_url":"https://patchwork.libcamera.org/comment/37970/","msgid":"<69e38997-03de-4517-8855-f6286bfd612b@collabora.com>","date":"2026-01-27T14:56:36","subject":"Re: [PATCH] libcamera: simple: Fix black level offsets in AWB","submitter":{"id":140,"url":"https://patchwork.libcamera.org/api/people/140/","name":"Robert Mader","email":"robert.mader@collabora.com"},"content":"Nice, this seems to help quite a bit with reducing green tint on some \nqcom devices (with black levels set in the tuning files).\n\nOn 27.01.26 13:37, Milan Zamazal wrote:\n> The black level offset subtracted in AWB is wrong. It assumes that the\n> stats contain sums of the individual colour pixels. But they actually\n> contain sums of the colour channels of larger \"superpixels\" consisting\n> of the individual colour pixels. Each of the RGB colour values and the\n> computed luminosity (a histogram entry) are added once to the stats per\n> such a superpixel. This means the offset computed from the black level\n> and the number of pixels should be used as it is, not divided.\n>\n> The patch fixes the subtracted offset. Since it is the same for all the\n> three colours, a SwIspStats helper method returning an RGB instance is\n> introduced. The individual colour variables are still retained in\n> SwIspStats for maximum efficiency when gathering the stats. SwIspStats\n> docstrings are changed to avoid the original confusion.\n>\n> Fixes: 4e13c6f55bd667 (\"Honor black level in AWB\")\n> Signed-off-by: Milan Zamazal \n> ---\n> .../internal/software_isp/swisp_stats.h | 17 +++++++++++++----\n> src/ipa/simple/algorithms/awb.cpp | 10 ++++------\n> 2 files changed, 17 insertions(+), 10 deletions(-)\n>\n> diff --git a/include/libcamera/internal/software_isp/swisp_stats.h b/include/libcamera/internal/software_isp/swisp_stats.h\n> index 3c9860185..f8816209f 100644\n> --- a/include/libcamera/internal/software_isp/swisp_stats.h\n> +++ b/include/libcamera/internal/software_isp/swisp_stats.h\n> @@ -10,6 +10,8 @@\n> #include \n> #include \n> \n> +#include \"libcamera/internal/vector.h\"\n> +\n> namespace libcamera {\n> \n> /**\n> @@ -26,17 +28,24 @@ struct SwIspStats {\n> \t */\n> \tbool valid;\n> \t/**\n> -\t * \\brief Holds the sum of all sampled red pixels\n> +\t * \\brief Holds the sum of red channels of all the sampled pixels\n> \t */\n> \tuint64_t sumR_;\n> \t/**\n> -\t * \\brief Holds the sum of all sampled green pixels\n> +\t * \\brief Holds the sum of green channels of all the sampled pixels\n> \t */\n> \tuint64_t sumG_;\n> \t/**\n> -\t * \\brief Holds the sum of all sampled blue pixels\n> +\t * \\brief Holds the sum of blue channels of all the sampled pixels\n> \t */\n> \tuint64_t sumB_;\n> +\t/**\n> +\t * \\brief Return the sums of colour channels of all the sampled pixels\n> +\t */\n> +\tRGB rgbSum() const\n> +\t{\n> +\t\treturn RGB({ sumR_, sumG_, sumB_ });\n> +\t}\n> \t/**\n> \t * \\brief Number of bins in the yHistogram\n> \t */\n> @@ -46,7 +55,7 @@ struct SwIspStats {\n> \t */\n> \tusing Histogram = std::array;\n> \t/**\n> -\t * \\brief A histogram of luminance values\n> +\t * \\brief A histogram of luminance values of all the sampled pixels\n> \t */\n> \tHistogram yHistogram;\n> };\n> diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp\n> index 0080865aa..4c8bfd2de 100644\n> --- a/src/ipa/simple/algorithms/awb.cpp\n> +++ b/src/ipa/simple/algorithms/awb.cpp\n> @@ -1,6 +1,6 @@\n> /* SPDX-License-Identifier: LGPL-2.1-or-later */\n> /*\n> - * Copyright (C) 2024, Red Hat Inc.\n> + * Copyright (C) 2024-2026 Red Hat Inc.\n> *\n> * Auto white balance\n> */\n> @@ -73,9 +73,7 @@ void Awb::process(IPAContext &context,\n> \t\thistogram.begin(), histogram.end(), uint64_t(0));\n> \tconst uint64_t offset = blackLevel * nPixels;\n> \tconst uint64_t minValid = 1;\n> -\tconst uint64_t sumR = stats->sumR_ > offset / 4 ? stats->sumR_ - offset / 4 : minValid;\n> -\tconst uint64_t sumG = stats->sumG_ > offset / 2 ? stats->sumG_ - offset / 2 : minValid;\n> -\tconst uint64_t sumB = stats->sumB_ > offset / 4 ? stats->sumB_ - offset / 4 : minValid;\n> +\tconst RGB sum = (stats->rgbSum() - offset).max(minValid);\n> \n> \t/*\n> \t * Calculate red and blue gains for AWB.\n> @@ -83,9 +81,9 @@ void Awb::process(IPAContext &context,\n> \t */\n> \tauto &gains = context.activeState.awb.gains;\n> \tgains = { {\n> -\t\tsumR <= sumG / 4 ? 4.0f : static_cast(sumG) / sumR,\n> +\t\tsum.r() <= sum.g() / 4 ? 4.0f : static_cast(sum.g()) / sum.r(),\n> \t\t1.0,\n> -\t\tsumB <= sumG / 4 ? 4.0f : static_cast(sumG) / sumB,\n> +\t\tsum.b() <= sum.g() / 4 ? 4.0f : static_cast(sum.g()) / sum.b(),\n> \t} };\n> \n> \tRGB rgbGains{ { 1 / gains.r(), 1 / gains.g(), 1 / gains.b() } };","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 1DEFBC3220\n\tfor ;\n\tTue, 27 Jan 2026 14:56:47 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 68FB361FC8;\n\tTue, 27 Jan 2026 15:56:46 +0100 (CET)","from sender4-op-o12.zoho.com (sender4-op-o12.zoho.com\n\t[136.143.188.12])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 7100761FBF\n\tfor ;\n\tTue, 27 Jan 2026 15:56:44 +0100 (CET)","by mx.zohomail.com with SMTPS id 1769525799556157.35793610915243; \n\tTue, 27 Jan 2026 06:56:39 -0800 (PST)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=collabora.com\n\theader.i=robert.mader@collabora.com header.b=\"Em7FVfC7\"; \n\tdkim-atps=neutral","ARC-Seal":"i=1; a=rsa-sha256; t=1769525801; cv=none; \n\td=zohomail.com; s=zohoarc; \n\tb=lA1OvaF9upwui1RIJt14fLY52WUSAiWp4GgQZYxpzJxmO63Yq1NFjg0u8H05GW6xmp7X1ZBcjddE7la/Im6NMat66/7YVuXuUuLSIbariuU1WJq0Acb93RDOyoAZNFJ/0tpbLgRA0j7LyVBJQYUCzhHF3dBl2Cg9oRdh0y0Q27U=","ARC-Message-Signature":"i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; \n\ts=zohoarc; t=1769525801;\n\th=Content-Type:Content-Transfer-Encoding:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To:Cc;\n\tbh=gXguXX3fVgGu7+IIoxQ63E0as/ULFCLB3T5lELD1yX0=; \n\tb=MM4RTlWAoTfk14NL1ZySTU7ll3Oue+GOBTZDzqQ7YSj38okmjWkqLQK4LY1KZCELZ6C0SGvIgFTxk/8VNOvzseZKXBmaGzFkrf8GGzQ1TQTPorGET0p69CNKdqS5cXM1mjSilqVMGexeAGxDrUsoOjKs4+xkBUkzqWOSY36yf0Y=","ARC-Authentication-Results":"i=1; mx.zohomail.com;\n\tdkim=pass header.i=collabora.com;\n\tspf=pass smtp.mailfrom=robert.mader@collabora.com;\n\tdmarc=pass header.from=","DKIM-Signature":"v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1769525801;\n\ts=zohomail; d=collabora.com; i=robert.mader@collabora.com;\n\th=Message-ID:Date:Date:MIME-Version:Subject:Subject:To:To:References:From:From:In-Reply-To:Content-Type:Content-Transfer-Encoding:Message-Id:Reply-To:Cc;\n\tbh=gXguXX3fVgGu7+IIoxQ63E0as/ULFCLB3T5lELD1yX0=;\n\tb=Em7FVfC7LFqYOfh227kdyfP01c2pqOki/h1d9zP/GPMSCgunybTqZZp04AOYnwWj\n\tixNWQhVdDCwQr9mREXGpuqqFfRCfzRpc+PFQxWHsP8MbSQ5URIikV/uL7XtEuB6+riX\n\tAo1nF0P0pNl2bLiSuQrFo4lv3gi/KNBgpfTeUzT4=","Message-ID":"<69e38997-03de-4517-8855-f6286bfd612b@collabora.com>","Date":"Tue, 27 Jan 2026 15:56:36 +0100","MIME-Version":"1.0","User-Agent":"Mozilla Thunderbird","Subject":"Re: [PATCH] libcamera: simple: Fix black level offsets in AWB","To":"libcamera-devel@lists.libcamera.org","References":"<20260127123728.70513-1-mzamazal@redhat.com>","Content-Language":"en-US, de-DE","From":"Robert Mader ","In-Reply-To":"<20260127123728.70513-1-mzamazal@redhat.com>","Content-Type":"text/plain; charset=UTF-8; format=flowed","Content-Transfer-Encoding":"7bit","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":37972,"web_url":"https://patchwork.libcamera.org/comment/37972/","msgid":"<85sebrt3tm.fsf@mzamazal-thinkpadp1gen7.tpbc.csb>","date":"2026-01-27T16:31:33","subject":"Re: [PATCH] libcamera: simple: Fix black level offsets in AWB","submitter":{"id":177,"url":"https://patchwork.libcamera.org/api/people/177/","name":"Milan Zamazal","email":"mzamazal@redhat.com"},"content":"Laurent Pinchart writes:\n\n> On Tue, Jan 27, 2026 at 01:37:28PM +0100, Milan Zamazal wrote:\n>> The black level offset subtracted in AWB is wrong. It assumes that the\n>> stats contain sums of the individual colour pixels. But they actually\n>\n>> contain sums of the colour channels of larger \"superpixels\" consisting\n>> of the individual colour pixels. Each of the RGB colour values and the\n>> computed luminosity (a histogram entry) are added once to the stats per\n>> such a superpixel. This means the offset computed from the black level\n>> and the number of pixels should be used as it is, not divided.\n>> \n>> The patch fixes the subtracted offset. Since it is the same for all the\n>> three colours, a SwIspStats helper method returning an RGB instance is\n>> introduced. The individual colour variables are still retained in\n>> SwIspStats for maximum efficiency when gathering the stats. SwIspStats\n>> docstrings are changed to avoid the original confusion.\n>> \n>> Fixes: 4e13c6f55bd667 (\"Honor black level in AWB\")\n>> Signed-off-by: Milan Zamazal \n>> ---\n>> .../internal/software_isp/swisp_stats.h | 17 +++++++++++++----\n>> src/ipa/simple/algorithms/awb.cpp | 10 ++++------\n>> 2 files changed, 17 insertions(+), 10 deletions(-)\n>> \n>> diff --git a/include/libcamera/internal/software_isp/swisp_stats.h b/include/libcamera/internal/software_isp/swisp_stats.h\n>> index 3c9860185..f8816209f 100644\n>> --- a/include/libcamera/internal/software_isp/swisp_stats.h\n>> +++ b/include/libcamera/internal/software_isp/swisp_stats.h\n>> @@ -10,6 +10,8 @@\n>> #include \n>> #include \n>> \n>> +#include \"libcamera/internal/vector.h\"\n>> +\n>> namespace libcamera {\n>> \n>> /**\n>> @@ -26,17 +28,24 @@ struct SwIspStats {\n>> \t */\n>> \tbool valid;\n>> \t/**\n>> -\t * \\brief Holds the sum of all sampled red pixels\n>> +\t * \\brief Holds the sum of red channels of all the sampled pixels\n>> \t */\n>> \tuint64_t sumR_;\n>> \t/**\n>> -\t * \\brief Holds the sum of all sampled green pixels\n>> +\t * \\brief Holds the sum of green channels of all the sampled pixels\n>> \t */\n>> \tuint64_t sumG_;\n>> \t/**\n>> -\t * \\brief Holds the sum of all sampled blue pixels\n>> +\t * \\brief Holds the sum of blue channels of all the sampled pixels\n>> \t */\n>> \tuint64_t sumB_;\n>> +\t/**\n>> +\t * \\brief Return the sums of colour channels of all the sampled pixels\n>> +\t */\n>> +\tRGB rgbSum() const\n>> +\t{\n>> +\t\treturn RGB({ sumR_, sumG_, sumB_ });\n>> +\t}\n>\n> I would have replaced all this with\n>\n> \tRGB sum_;\n\nOK, I measured the performance impact and there is none in my\nenvironment. Done in v2.\n\n> (with an appropriate documentation block)\n\nI don't feel particularly creative here for an internal structure. Do\nwe need to mention anything special here?\n\n>> \t/**\n>> \t * \\brief Number of bins in the yHistogram\n>> \t */\n>> @@ -46,7 +55,7 @@ struct SwIspStats {\n>> \t */\n>> \tusing Histogram = std::array;\n>> \t/**\n>> -\t * \\brief A histogram of luminance values\n>> +\t * \\brief A histogram of luminance values of all the sampled pixels\n>> \t */\n>> \tHistogram yHistogram;\n>> };\n>> diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp\n>> index 0080865aa..4c8bfd2de 100644\n>> --- a/src/ipa/simple/algorithms/awb.cpp\n>> +++ b/src/ipa/simple/algorithms/awb.cpp\n>> @@ -1,6 +1,6 @@\n>> /* SPDX-License-Identifier: LGPL-2.1-or-later */\n>> /*\n>> - * Copyright (C) 2024, Red Hat Inc.\n>> + * Copyright (C) 2024-2026 Red Hat Inc.\n>> *\n>> * Auto white balance\n>> */\n>> @@ -73,9 +73,7 @@ void Awb::process(IPAContext &context,\n>> \t\thistogram.begin(), histogram.end(), uint64_t(0));\n>> \tconst uint64_t offset = blackLevel * nPixels;\n>> \tconst uint64_t minValid = 1;\n>> -\tconst uint64_t sumR = stats->sumR_ > offset / 4 ? stats->sumR_ - offset / 4 : minValid;\n>> -\tconst uint64_t sumG = stats->sumG_ > offset / 2 ? stats->sumG_ - offset / 2 : minValid;\n>> -\tconst uint64_t sumB = stats->sumB_ > offset / 4 ? stats->sumB_ - offset / 4 : minValid;\n>> +\tconst RGB sum = (stats->rgbSum() - offset).max(minValid);\n>> \n>> \t/*\n>> \t * Calculate red and blue gains for AWB.\n>> @@ -83,9 +81,9 @@ void Awb::process(IPAContext &context,\n>> \t */\n>> \tauto &gains = context.activeState.awb.gains;\n>> \tgains = { {\n>> -\t\tsumR <= sumG / 4 ? 4.0f : static_cast(sumG) / sumR,\n>> +\t\tsum.r() <= sum.g() / 4 ? 4.0f : static_cast(sum.g()) / sum.r(),\n>> \t\t1.0,\n>> -\t\tsumB <= sumG / 4 ? 4.0f : static_cast(sumG) / sumB,\n>> +\t\tsum.b() <= sum.g() / 4 ? 4.0f : static_cast(sum.g()) / sum.b(),\n>> \t} };\n>> \n>> \tRGB rgbGains{ { 1 / gains.r(), 1 / gains.g(), 1 / gains.b() } };","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 6874BC3200\n\tfor ;\n\tTue, 27 Jan 2026 16:31:42 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 600A261FC8;\n\tTue, 27 Jan 2026 17:31:41 +0100 (CET)","from us-smtp-delivery-124.mimecast.com\n\t(us-smtp-delivery-124.mimecast.com [170.10.133.124])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id BF3B961FBF\n\tfor ;\n\tTue, 27 Jan 2026 17:31:39 +0100 (CET)","from mail-wr1-f70.google.com (mail-wr1-f70.google.com\n\t[209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS\n\t(version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id\n\tus-mta-170-1jGRSF-PMN-KyIQntmTpcg-1; Tue, 27 Jan 2026 11:31:37 -0500","by mail-wr1-f70.google.com with SMTP id\n\tffacd0b85a97d-430fcfe4494so5426642f8f.2\n\tfor ;\n\tTue, 27 Jan 2026 08:31:37 -0800 (PST)","from mzamazal-thinkpadp1gen7.tpbc.csb\n\t(ip-77-48-47-2.net.vodafone.cz. 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It assumes that the\n>> stats contain sums of the individual colour pixels. But they actually\n>> contain sums of the colour channels of larger \"superpixels\" consisting\n>> of the individual colour pixels. Each of the RGB colour values and the\n>> computed luminosity (a histogram entry) are added once to the stats per\n>> such a superpixel. This means the offset computed from the black level\n>> and the number of pixels should be used as it is, not divided.\n>>\n>> The patch fixes the subtracted offset. Since it is the same for all the\n>> three colours, a SwIspStats helper method returning an RGB instance is\n>> introduced. The individual colour variables are still retained in\n>> SwIspStats for maximum efficiency when gathering the stats. SwIspStats\n>> docstrings are changed to avoid the original confusion.\n>>\n>> Fixes: 4e13c6f55bd667 (\"Honor black level in AWB\")\n>> Signed-off-by: Milan Zamazal \n>> ---\n>> .../internal/software_isp/swisp_stats.h | 17 +++++++++++++----\n>> src/ipa/simple/algorithms/awb.cpp | 10 ++++------\n>> 2 files changed, 17 insertions(+), 10 deletions(-)\n>>\n>> diff --git a/include/libcamera/internal/software_isp/swisp_stats.h b/include/libcamera/internal/software_isp/swisp_stats.h\n>> index 3c9860185..f8816209f 100644\n>> --- a/include/libcamera/internal/software_isp/swisp_stats.h\n>> +++ b/include/libcamera/internal/software_isp/swisp_stats.h\n>> @@ -10,6 +10,8 @@\n>> #include \n>> #include \n>> +#include \"libcamera/internal/vector.h\"\n>> +\n>> namespace libcamera {\n>> /**\n>> @@ -26,17 +28,24 @@ struct SwIspStats {\n>> \t */\n>> \tbool valid;\n>> \t/**\n>> -\t * \\brief Holds the sum of all sampled red pixels\n>> +\t * \\brief Holds the sum of red channels of all the sampled pixels\n>> \t */\n>> \tuint64_t sumR_;\n>> \t/**\n>> -\t * \\brief Holds the sum of all sampled green pixels\n>> +\t * \\brief Holds the sum of green channels of all the sampled pixels\n>> \t */\n>> \tuint64_t sumG_;\n>> \t/**\n>> -\t * \\brief Holds the sum of all sampled blue pixels\n>> +\t * \\brief Holds the sum of blue channels of all the sampled pixels\n>> \t */\n>> \tuint64_t sumB_;\n>> +\t/**\n>> +\t * \\brief Return the sums of colour channels of all the sampled pixels\n>> +\t */\n>> +\tRGB rgbSum() const\n>> +\t{\n>> +\t\treturn RGB({ sumR_, sumG_, sumB_ });\n>> +\t}\n>> \t/**\n>> \t * \\brief Number of bins in the yHistogram\n>> \t */\n>> @@ -46,7 +55,7 @@ struct SwIspStats {\n>> \t */\n>> \tusing Histogram = std::array;\n>> \t/**\n>> -\t * \\brief A histogram of luminance values\n>> +\t * \\brief A histogram of luminance values of all the sampled pixels\n>> \t */\n>> \tHistogram yHistogram;\n>> };\n>> diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp\n>> index 0080865aa..4c8bfd2de 100644\n>> --- a/src/ipa/simple/algorithms/awb.cpp\n>> +++ b/src/ipa/simple/algorithms/awb.cpp\n>> @@ -1,6 +1,6 @@\n>> /* SPDX-License-Identifier: LGPL-2.1-or-later */\n>> /*\n>> - * Copyright (C) 2024, Red Hat Inc.\n>> + * Copyright (C) 2024-2026 Red Hat Inc.\n>> *\n>> * Auto white balance\n>> */\n>> @@ -73,9 +73,7 @@ void Awb::process(IPAContext &context,\n>> \t\thistogram.begin(), histogram.end(), uint64_t(0));\n>> \tconst uint64_t offset = blackLevel * nPixels;\n>> \tconst uint64_t minValid = 1;\n>> -\tconst uint64_t sumR = stats->sumR_ > offset / 4 ? stats->sumR_ - offset / 4 : minValid;\n>> -\tconst uint64_t sumG = stats->sumG_ > offset / 2 ? stats->sumG_ - offset / 2 : minValid;\n>> -\tconst uint64_t sumB = stats->sumB_ > offset / 4 ? stats->sumB_ - offset / 4 : minValid;\n>> +\tconst RGB sum = (stats->rgbSum() - offset).max(minValid);\n>> \t/*\n>> \t * Calculate red and blue gains for AWB.\n>> @@ -83,9 +81,9 @@ void Awb::process(IPAContext &context,\n>> \t */\n>> \tauto &gains = context.activeState.awb.gains;\n>> \tgains = { {\n>> -\t\tsumR <= sumG / 4 ? 4.0f : static_cast(sumG) / sumR,\n>> +\t\tsum.r() <= sum.g() / 4 ? 4.0f : static_cast(sum.g()) / sum.r(),\n>> \t\t1.0,\n>> -\t\tsumB <= sumG / 4 ? 4.0f : static_cast(sumG) / sumB,\n>> +\t\tsum.b() <= sum.g() / 4 ? 4.0f : static_cast(sum.g()) / sum.b(),\n>> \t} };\n>> \tRGB rgbGains{ { 1 / gains.r(), 1 / gains.g(), 1 / gains.b() } };","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 2D0BCC3220\n\tfor ;\n\tTue, 27 Jan 2026 16:37:24 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 5142D61FC8;\n\tTue, 27 Jan 2026 17:37:23 +0100 (CET)","from us-smtp-delivery-124.mimecast.com\n\t(us-smtp-delivery-124.mimecast.com [170.10.133.124])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id D1DC261FBF\n\tfor ;\n\tTue, 27 Jan 2026 17:37:21 +0100 (CET)","from mail-wm1-f70.google.com (mail-wm1-f70.google.com\n\t[209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS\n\t(version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id\n\tus-mta-396-Jeavdoh7NNKtAEfEpL4rpw-1; Tue, 27 Jan 2026 11:37:18 -0500","by mail-wm1-f70.google.com with SMTP id\n\t5b1f17b1804b1-47ee1fe7b24so50726655e9.1\n\tfor ;\n\tTue, 27 Jan 2026 08:37:18 -0800 (PST)","from mzamazal-thinkpadp1gen7.tpbc.csb\n\t(ip-77-48-47-2.net.vodafone.cz. 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It assumes that the\n> >> stats contain sums of the individual colour pixels. But they actually\n> >\n> >> contain sums of the colour channels of larger \"superpixels\" consisting\n> >> of the individual colour pixels. Each of the RGB colour values and the\n> >> computed luminosity (a histogram entry) are added once to the stats per\n> >> such a superpixel. This means the offset computed from the black level\n> >> and the number of pixels should be used as it is, not divided.\n> >> \n> >> The patch fixes the subtracted offset. Since it is the same for all the\n> >> three colours, a SwIspStats helper method returning an RGB instance is\n> >> introduced. The individual colour variables are still retained in\n> >> SwIspStats for maximum efficiency when gathering the stats. SwIspStats\n> >> docstrings are changed to avoid the original confusion.\n> >> \n> >> Fixes: 4e13c6f55bd667 (\"Honor black level in AWB\")\n> >> Signed-off-by: Milan Zamazal \n> >> ---\n> >> .../internal/software_isp/swisp_stats.h | 17 +++++++++++++----\n> >> src/ipa/simple/algorithms/awb.cpp | 10 ++++------\n> >> 2 files changed, 17 insertions(+), 10 deletions(-)\n> >> \n> >> diff --git a/include/libcamera/internal/software_isp/swisp_stats.h b/include/libcamera/internal/software_isp/swisp_stats.h\n> >> index 3c9860185..f8816209f 100644\n> >> --- a/include/libcamera/internal/software_isp/swisp_stats.h\n> >> +++ b/include/libcamera/internal/software_isp/swisp_stats.h\n> >> @@ -10,6 +10,8 @@\n> >> #include \n> >> #include \n> >> \n> >> +#include \"libcamera/internal/vector.h\"\n> >> +\n> >> namespace libcamera {\n> >> \n> >> /**\n> >> @@ -26,17 +28,24 @@ struct SwIspStats {\n> >> \t */\n> >> \tbool valid;\n> >> \t/**\n> >> -\t * \\brief Holds the sum of all sampled red pixels\n> >> +\t * \\brief Holds the sum of red channels of all the sampled pixels\n> >> \t */\n> >> \tuint64_t sumR_;\n> >> \t/**\n> >> -\t * \\brief Holds the sum of all sampled green pixels\n> >> +\t * \\brief Holds the sum of green channels of all the sampled pixels\n> >> \t */\n> >> \tuint64_t sumG_;\n> >> \t/**\n> >> -\t * \\brief Holds the sum of all sampled blue pixels\n> >> +\t * \\brief Holds the sum of blue channels of all the sampled pixels\n> >> \t */\n> >> \tuint64_t sumB_;\n> >> +\t/**\n> >> +\t * \\brief Return the sums of colour channels of all the sampled pixels\n> >> +\t */\n> >> +\tRGB rgbSum() const\n> >> +\t{\n> >> +\t\treturn RGB({ sumR_, sumG_, sumB_ });\n> >> +\t}\n> >\n> > I would have replaced all this with\n> >\n> > \tRGB sum_;\n> \n> OK, I measured the performance impact and there is none in my\n> environment. Done in v2.\n> \n> > (with an appropriate documentation block)\n> \n> I don't feel particularly creative here for an internal structure. Do\n> we need to mention anything special here?\n\nNo, I just mentioned it to make it clear I wasn't suggesting dropping\nthe documentation. Something like\n\n\t/**\n\t * \\brief The sum of all sampled pixels, separately for R, G and B.\n\t */\n\nwould do.\n\n> >> \t/**\n> >> \t * \\brief Number of bins in the yHistogram\n> >> \t */\n> >> @@ -46,7 +55,7 @@ struct SwIspStats {\n> >> \t */\n> >> \tusing Histogram = std::array;\n> >> \t/**\n> >> -\t * \\brief A histogram of luminance values\n> >> +\t * \\brief A histogram of luminance values of all the sampled pixels\n> >> \t */\n> >> \tHistogram yHistogram;\n> >> };\n> >> diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp\n> >> index 0080865aa..4c8bfd2de 100644\n> >> --- a/src/ipa/simple/algorithms/awb.cpp\n> >> +++ b/src/ipa/simple/algorithms/awb.cpp\n> >> @@ -1,6 +1,6 @@\n> >> /* SPDX-License-Identifier: LGPL-2.1-or-later */\n> >> /*\n> >> - * Copyright (C) 2024, Red Hat Inc.\n> >> + * Copyright (C) 2024-2026 Red Hat Inc.\n> >> *\n> >> * Auto white balance\n> >> */\n> >> @@ -73,9 +73,7 @@ void Awb::process(IPAContext &context,\n> >> \t\thistogram.begin(), histogram.end(), uint64_t(0));\n> >> \tconst uint64_t offset = blackLevel * nPixels;\n> >> \tconst uint64_t minValid = 1;\n> >> -\tconst uint64_t sumR = stats->sumR_ > offset / 4 ? stats->sumR_ - offset / 4 : minValid;\n> >> -\tconst uint64_t sumG = stats->sumG_ > offset / 2 ? stats->sumG_ - offset / 2 : minValid;\n> >> -\tconst uint64_t sumB = stats->sumB_ > offset / 4 ? stats->sumB_ - offset / 4 : minValid;\n> >> +\tconst RGB sum = (stats->rgbSum() - offset).max(minValid);\n> >> \n> >> \t/*\n> >> \t * Calculate red and blue gains for AWB.\n> >> @@ -83,9 +81,9 @@ void Awb::process(IPAContext &context,\n> >> \t */\n> >> \tauto &gains = context.activeState.awb.gains;\n> >> \tgains = { {\n> >> -\t\tsumR <= sumG / 4 ? 4.0f : static_cast(sumG) / sumR,\n> >> +\t\tsum.r() <= sum.g() / 4 ? 4.0f : static_cast(sum.g()) / sum.r(),\n> >> \t\t1.0,\n> >> -\t\tsumB <= sumG / 4 ? 4.0f : static_cast(sumG) / sumB,\n> >> +\t\tsum.b() <= sum.g() / 4 ? 4.0f : static_cast(sum.g()) / sum.b(),\n> >> \t} };\n> >> \n> >> \tRGB rgbGains{ { 1 / gains.r(), 1 / gains.g(), 1 / gains.b() } };","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id A6462C3220\n\tfor ;\n\tTue, 27 Jan 2026 16:40:18 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id CC81D61FC8;\n\tTue, 27 Jan 2026 17:40:17 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 2443C61FBF\n\tfor ;\n\tTue, 27 Jan 2026 17:40:17 +0100 (CET)","from pendragon.ideasonboard.com\n\t(2001-14ba-703d-e500--2a1.rev.dnainternet.fi\n\t[IPv6:2001:14ba:703d:e500::2a1])\n\tby perceval.ideasonboard.com (Postfix) with UTF8SMTPSA id A4976465;\n\tTue, 27 Jan 2026 17:39:40 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"OS4wcC86\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1769531980;\n\tbh=oeOxa47fJw6q451nFV5jHbmyx8zi8nEErP4bKx1Dhxg=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=OS4wcC86BvzH+pQtn2mcjBsvvrLqwXyE8i92/JYbCZ6+pA0RCRry4hIx4YztcOkf5\n\tQD9PU/t863EjRF6PFuEd6op9MX8FUU+fA3ul6OPI6Y+de4YmlusjmF9xamYKOmWCy/\n\tQ+/Hez1L53D16BZu83h3nK1WIl9BkCk2lgyje1zQ=","Date":"Tue, 27 Jan 2026 18:40:15 +0200","From":"Laurent Pinchart ","To":"Milan Zamazal ","Cc":"libcamera-devel@lists.libcamera.org","Subject":"Re: [PATCH] libcamera: simple: Fix black level offsets in AWB","Message-ID":"<20260127164015.GA2512313@killaraus>","References":"<20260127123728.70513-1-mzamazal@redhat.com>\n\t<20260127144731.GA2502390@killaraus>\n\t<85sebrt3tm.fsf@mzamazal-thinkpadp1gen7.tpbc.csb>","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"<85sebrt3tm.fsf@mzamazal-thinkpadp1gen7.tpbc.csb>","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}}]