From patchwork Tue Apr 1 12:36:13 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Klug X-Patchwork-Id: 23092 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 9A312C3213 for ; Tue, 1 Apr 2025 12:36:56 +0000 (UTC) Received: from lancelot.ideasonboard.com (localhost [IPv6:::1]) by lancelot.ideasonboard.com (Postfix) with ESMTP id 53C9768991; Tue, 1 Apr 2025 14:36:56 +0200 (CEST) Authentication-Results: lancelot.ideasonboard.com; dkim=pass (1024-bit key; unprotected) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="AyH8eUBd"; dkim-atps=neutral Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647]) by lancelot.ideasonboard.com (Postfix) with ESMTPS id E73F66898A for ; Tue, 1 Apr 2025 14:36:53 +0200 (CEST) Received: from ideasonboard.com (unknown [IPv6:2a00:6020:448c:6c00:14c7:4fcc:495b:719f]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id CA2968DB; Tue, 1 Apr 2025 14:35:01 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1743510901; bh=bUNDK7vLq1vWyOMPzMZ+ZDpn7eKJqeahqSjxAG4P9vE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AyH8eUBdAqscnPyY8wzlkNDpxBLvUDycIIwG7hpqSusEAKoI0diQAO9jkFlOyv02z z7g3Z9UkJ3KrOe9PnUT0u+FSl57Op/eXFQgUhi5aePRuXNm4eZ2R7Yli5By1GWdus0 mFf3Gv3utMV0Ew2N4q6lFuymSIts8PpyCIkGXV3g= From: Stefan Klug To: libcamera-devel@lists.libcamera.org Cc: Stefan Klug , Kieran Bingham , Laurent Pinchart Subject: [PATCH v2 5/5] libipa: histogram: Fix interQuantileMean() for small ranges Date: Tue, 1 Apr 2025 14:36:13 +0200 Message-ID: <20250401123633.58887-6-stefan.klug@ideasonboard.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250401123633.58887-1-stefan.klug@ideasonboard.com> References: <20250401123633.58887-1-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 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 --- Changes in v2: - Order fix patch after test patch - Remove should_fail - Added documentation based on review - Improved code style based on review --- src/ipa/libipa/histogram.cpp | 39 +++++++++++++++++++++++------------- test/ipa/libipa/meson.build | 2 +- 2 files changed, 26 insertions(+), 15 deletions(-) diff --git a/src/ipa/libipa/histogram.cpp b/src/ipa/libipa/histogram.cpp index ea042f0a17b9..bcf263908236 100644 --- a/src/ipa/libipa/histogram.cpp +++ b/src/ipa/libipa/histogram.cpp @@ -149,26 +149,37 @@ double Histogram::quantile(double q, uint32_t first, uint32_t last) const double Histogram::interQuantileMean(double lowQuantile, double highQuantile) const { ASSERT(highQuantile > lowQuantile); - /* Proportion of pixels which lies below lowQuantile */ - double lowPoint = quantile(lowQuantile); - /* Proportion of pixels which lies below highQuantile */ - double highPoint = quantile(highQuantile, static_cast(lowPoint)); - double sumBinFreq = 0, cumulFreq = 0; - - for (double p_next = floor(lowPoint) + 1.0; - p_next <= ceil(highPoint); - lowPoint = p_next, p_next += 1.0) { - int bin = floor(lowPoint); + + /* Proportion of pixels which lies below lowQuantile and highQuantile. */ + const double lowPoint = quantile(lowQuantile); + const double highPoint = quantile(highQuantile, static_cast(lowPoint)); + + double sumBinFreq = 0; + double cumulFreq = 0; + + /* + * Calculate the mean pixel value between the low and high points by + * summing all the pixels between the two points, and dividing the sum + * by the number of pixels. Given the discrete nature of the histogram + * data, the sum of the pixels is approximated by accumulating the + * product of the bin values (calculated as the mid point of the bin) by + * the number of pixels they contain, for each bin in the internal. + */ + for (unsigned bin = std::floor(lowPoint); bin < std::ceil(highPoint); bin++) { + const double lowBound = std::max(bin, lowPoint); + const double highBound = std::min(bin + 1, highPoint); + double freq = (cumulative_[bin + 1] - cumulative_[bin]) - * (std::min(p_next, highPoint) - lowPoint); + * (highBound - lowBound); /* Accumulate weighted bin */ - sumBinFreq += bin * freq; + sumBinFreq += (highBound + lowBound) / 2 * 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 */ diff --git a/test/ipa/libipa/meson.build b/test/ipa/libipa/meson.build index 83c84bd8c227..8c63ebd8e2f7 100644 --- a/test/ipa/libipa/meson.build +++ b/test/ipa/libipa/meson.build @@ -2,7 +2,7 @@ libipa_test = [ {'name': 'fixedpoint', 'sources': ['fixedpoint.cpp']}, - {'name': 'histogram', 'sources': ['histogram.cpp'], 'should_fail': true}, + {'name': 'histogram', 'sources': ['histogram.cpp']}, {'name': 'interpolator', 'sources': ['interpolator.cpp']}, ]