From patchwork Mon Mar 24 17:07:39 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Klug X-Patchwork-Id: 23005 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 F00EBC3213 for ; Mon, 24 Mar 2025 17:08:27 +0000 (UTC) Received: from lancelot.ideasonboard.com (localhost [IPv6:::1]) by lancelot.ideasonboard.com (Postfix) with ESMTP id AE3F76895F; Mon, 24 Mar 2025 18:08:27 +0100 (CET) Authentication-Results: lancelot.ideasonboard.com; dkim=pass (1024-bit key; unprotected) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="Vap0Xg5G"; dkim-atps=neutral Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by lancelot.ideasonboard.com (Postfix) with ESMTPS id 693CA6895D for ; Mon, 24 Mar 2025 18:08:25 +0100 (CET) Received: from ideasonboard.com (unknown [IPv6:2a00:6020:448c:6c00:854:5bc6:b2a7:e242]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id CDA5AA8F; Mon, 24 Mar 2025 18:06:38 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1742835998; bh=0uGFCAEhZMyiQcNIKO7XXs1LGnUKZrRebehhUvhFAsU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Vap0Xg5GjqNzJwi3qdv1hBSge11DQmlaes9qOJt6I/StWxsJqSgrl1x777XcLBnjL stuuF96Fr1ikPqVbeRePex/+DO5k+KGJ51IcLgRJ21P+u/oHqSwe5kQiMcowFUSEgY gbs6RFeGJ3pdvI6vnyQTTQuk4PEbmnjPtfLlxcnM= From: Stefan Klug To: libcamera-devel@lists.libcamera.org Cc: Stefan Klug Subject: [PATCH 4/5] libipa: histogram: Fix interQuantileMean() for small ranges Date: Mon, 24 Mar 2025 18:07:39 +0100 Message-ID: <20250324170803.103296-5-stefan.klug@ideasonboard.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250324170803.103296-1-stefan.klug@ideasonboard.com> References: <20250324170803.103296-1-stefan.klug@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" The interQuantileMean() is supposed to return a weighted mean value between two quantiles. This works for reasonably fine histograms, but fails for coarse histograms and small quantile ranges because the weight is always taken from the lower border of the bin. Fix that by rewriting the algorithm to calculate a lower and upper bound for every (partial) bin that goes into the mean calculation and weight the bins by the middle of these bounds. Signed-off-by: Stefan Klug Acked-by: Kieran Bingham Reviewed-by: Laurent Pinchart --- src/ipa/libipa/histogram.cpp | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) diff --git a/src/ipa/libipa/histogram.cpp b/src/ipa/libipa/histogram.cpp index c19a4cbbf3cd..31f017af3458 100644 --- a/src/ipa/libipa/histogram.cpp +++ b/src/ipa/libipa/histogram.cpp @@ -153,22 +153,24 @@ double Histogram::interQuantileMean(double lowQuantile, double highQuantile) con double lowPoint = quantile(lowQuantile); /* Proportion of pixels which lies below highQuantile */ double highPoint = quantile(highQuantile, static_cast(lowPoint)); - double sumBinFreq = 0, cumulFreq = 0; + double sumBinFreq = 0; + double cumulFreq = 0; + + for (int bin = std::floor(lowPoint); bin < std::ceil(highPoint); bin++) { + double lowBound = std::max(static_cast(bin), lowPoint); + double highBound = std::min(static_cast(bin + 1), highPoint); - for (double p_next = floor(lowPoint) + 1.0; - p_next <= ceil(highPoint); - lowPoint = p_next, p_next += 1.0) { - int bin = floor(lowPoint); double freq = (cumulative_[bin + 1] - cumulative_[bin]) - * (std::min(p_next, highPoint) - lowPoint); + * (highBound - lowBound); /* Accumulate weighted bin */ - sumBinFreq += bin * freq; + sumBinFreq += 0.5 * (highBound + lowBound) * freq; + /* Accumulate weights */ cumulFreq += freq; } - /* add 0.5 to give an average for bin mid-points */ - return sumBinFreq / cumulFreq + 0.5; + + return sumBinFreq / cumulFreq; } } /* namespace ipa */