From patchwork Mon Aug 3 13:14:25 2026 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= X-Patchwork-Id: 27589 Return-Path: X-Original-To: parsemail@patchwork.libcamera.org Delivered-To: parsemail@patchwork.libcamera.org Received: from lancelot.ideasonboard.com (lancelot.ideasonboard.com [92.243.16.209]) by patchwork.libcamera.org (Postfix) with ESMTPS id 44272C3348 for ; Mon, 3 Aug 2026 13:15:23 +0000 (UTC) Received: from lancelot.ideasonboard.com (localhost [IPv6:::1]) by lancelot.ideasonboard.com (Postfix) with ESMTP id 49AF6680FC; Mon, 3 Aug 2026 15:15:20 +0200 (CEST) Authentication-Results: lancelot.ideasonboard.com; dkim=pass (1024-bit key; unprotected) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="M/5lBKz6"; dkim-atps=neutral Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by lancelot.ideasonboard.com (Postfix) with ESMTPS id DBB5E680B4 for ; Mon, 3 Aug 2026 15:14:47 +0200 (CEST) Received: from pb-laptop.local (185.221.141.208.nat.pool.zt.hu [185.221.141.208]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 06E085B3 for ; Mon, 3 Aug 2026 15:13:39 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1785762819; bh=Ch7Eiq1lpvW3U4J8QDDus2uEA7uHeblo7NL8vJMXO1U=; h=From:To:Subject:Date:In-Reply-To:References:From; b=M/5lBKz6U37LiY7zSnbA3c6NrOfaPBd8HysWWwmhHcw7Usj7wcUzm9tnh8c/9Mo6N Vao76eea+reNTgbNZ8Py20aY1MLpcR/uwBAhGd+kzMAr2pat+Mx7XpvkQmt0Hg+X2h prS/b3Pv2t8lp9gdJS3qlvN9Dju/mYuGZefepiyw= From: =?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= To: libcamera-devel@lists.libcamera.org Subject: [RFC PATCH v3 40/50] ipa: simple: agc: Adjust histogram for black level Date: Mon, 3 Aug 2026 15:14:25 +0200 Message-ID: <20260803131435.153927-41-barnabas.pocze@ideasonboard.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260803131435.153927-1-barnabas.pocze@ideasonboard.com> References: <20260803131435.153927-1-barnabas.pocze@ideasonboard.com> MIME-Version: 1.0 X-BeenThere: libcamera-devel@lists.libcamera.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libcamera-devel-bounces@lists.libcamera.org Sender: "libcamera-devel" Instead of providing the black separately, adjust the luminance histogram according to the current black level. This changes the behaviour slightly as previously everything under the black level was ignored, and only the remaining part was split into the 5 bins, but now the full histogram is split into the 5 bins. TODO: or should the previous behaviour be preserved and a smaller histogram be used without adjustments? TODO: is it `i < blackLevelHistIdx` or `i <= blackLevelHistIdx` ??? Signed-off-by: Barnabás Pőcze --- src/ipa/simple/algorithms/agc.cpp | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/src/ipa/simple/algorithms/agc.cpp b/src/ipa/simple/algorithms/agc.cpp index cc33b269bf..199b444f5a 100644 --- a/src/ipa/simple/algorithms/agc.cpp +++ b/src/ipa/simple/algorithms/agc.cpp @@ -11,6 +11,7 @@ #include #include #include +#include #include @@ -66,19 +67,15 @@ static constexpr float kExpMaxStep = 0.15; namespace { -std::optional calculateMSV(const Histogram &histogram, uint8_t blackLevel) +std::optional calculateMSV(const Histogram &histogram) { /* * Calculate Mean Sample Value (MSV) according to formula from: * https://www.araa.asn.au/acra/acra2007/papers/paper84final.pdf */ - const unsigned int blackLevelHistIdx = - blackLevel * histogram.bins() / 256; - const unsigned int histogramSize = - histogram.bins() - blackLevelHistIdx; - const unsigned int yHistValsPerBin = histogramSize / kExposureBinsCount; + const unsigned int yHistValsPerBin = histogram.bins() / kExposureBinsCount; const unsigned int yHistValsPerBinMod = - histogramSize / (histogramSize % kExposureBinsCount + 1); + histogram.bins() / (histogram.bins() % kExposureBinsCount + 1); int exposureBins[kExposureBinsCount] = {}; unsigned int denom = 0; unsigned int num = 0; @@ -86,9 +83,9 @@ std::optional calculateMSV(const Histogram &histogram, uint8_t blackLevel if (yHistValsPerBin == 0) return {}; - for (unsigned int i = 0; i < histogramSize; i++) { + for (unsigned int i = 0; i < histogram.bins(); i++) { unsigned int idx = (i - (i / yHistValsPerBinMod)) / yHistValsPerBin; - exposureBins[idx] += histogram[blackLevelHistIdx + i]; + exposureBins[idx] += histogram[i]; } for (unsigned int i = 0; i < kExposureBinsCount; i++) { @@ -193,7 +190,14 @@ void Agc::process(IPAContext &context, return; } - auto exposureMSV = calculateMSV({ stats->yHistogram }, context.activeState.blc.level); + auto histogram = stats->yHistogram; + const unsigned int blackLevelHistIdx = + context.activeState.blc.level * std::size(histogram) / 256; + + for (unsigned int i = 1; i < blackLevelHistIdx; i++) + histogram[0] += std::exchange(histogram[i], 0); + + auto exposureMSV = calculateMSV({ histogram }); if (!exposureMSV) { LOG(IPASoftExposure, Debug) << "Not adjusting exposure due to insufficient histogram data";