[{"id":35913,"web_url":"https://patchwork.libcamera.org/comment/35913/","msgid":"","date":"2025-09-19T04:15:31","subject":"Re: [PATCH v2 4/6] libcamera: simple: Avoid incorrect arithmetic in\n\tAWB","submitter":{"id":237,"url":"https://patchwork.libcamera.org/api/people/237/","name":"Maciej S. Szmigiero","email":"mail@maciej.szmigiero.name"},"content":"On 9/11/25 15:51, Milan Zamazal wrote:\n> The R/G/B sums computed in AWB simple IPA may be zero or perhaps even\n> negative. Let's make sure the sums are always positive, to prevent\n> division by zero or completely nonsense results.\n> \n> Signed-off-by: Milan Zamazal \n> ---\n> src/ipa/simple/algorithms/awb.cpp | 8 +++++---\n> 1 file changed, 5 insertions(+), 3 deletions(-)\n> \n> diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp\n> index cf567e894..9509129e9 100644\n> --- a/src/ipa/simple/algorithms/awb.cpp\n> +++ b/src/ipa/simple/algorithms/awb.cpp\n> @@ -7,6 +7,7 @@\n> \n> #include \"awb.h\"\n> \n> +#include \n> #include \n> #include \n> \n> @@ -69,9 +70,10 @@ void Awb::process(IPAContext &context,\n> \tconst uint64_t nPixels = std::accumulate(\n> \t\thistogram.begin(), histogram.end(), 0);\n> \tconst uint64_t offset = blackLevel * nPixels;\n> -\tconst uint64_t sumR = stats->sumR_ - offset / 4;\n> -\tconst uint64_t sumG = stats->sumG_ - offset / 2;\n> -\tconst uint64_t sumB = stats->sumB_ - offset / 4;\n> +\tconst uint64_t minValid = 1;\n> +\tconst uint64_t sumR = std::max(stats->sumR_ - offset / 4, minValid);\n> +\tconst uint64_t sumG = std::max(stats->sumG_ - offset / 2, minValid);\n> +\tconst uint64_t sumB = std::max(stats->sumB_ - offset / 4, minValid);\n\nIt looks like stats->sumR_ and offset are both unsigned integers so\nI guess they won't ever go negative?\n\nIn this case if (offset / 4) > stats->sumR_ the result will be a large\npositive value.\n\nThanks,\nMacoej","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 29F65C328C\n\tfor ;\n\tFri, 19 Sep 2025 04:15:37 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 0355D6B594;\n\tFri, 19 Sep 2025 06:15:36 +0200 (CEST)","from vps-ovh.mhejs.net (vps-ovh.mhejs.net [145.239.82.108])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 49B6369367\n\tfor ;\n\tFri, 19 Sep 2025 06:15:34 +0200 (CEST)","from MUA\n\tby vps-ovh.mhejs.net with esmtpsa (TLS1.3) tls TLS_AES_128_GCM_SHA256\n\t(Exim 4.98.2) (envelope-from )\n\tid 1uzSWz-00000002yUG-30aF; Fri, 19 Sep 2025 06:15:33 +0200"],"Message-ID":"","Date":"Fri, 19 Sep 2025 06:15:31 +0200","MIME-Version":"1.0","User-Agent":"Mozilla Thunderbird","Subject":"Re: [PATCH v2 4/6] libcamera: simple: Avoid incorrect arithmetic in\n\tAWB","To":"Milan Zamazal ","Cc":"pobrn@protonmail.com, libcamera-devel@lists.libcamera.org","References":"<20250911135144.56586-1-mzamazal@redhat.com>\n\t<20250911135144.56586-5-mzamazal@redhat.com>","Content-Language":"en-US","From":"\"Maciej S. Szmigiero\" ","Autocrypt":"addr=mail@maciej.szmigiero.name; keydata=\n\txsFNBFpGusUBEADXUMM2t7y9sHhI79+2QUnDdpauIBjZDukPZArwD+sDlx5P+jxaZ13XjUQc\n\t6oJdk+jpvKiyzlbKqlDtw/Y2Ob24tg1g/zvkHn8AVUwX+ZWWewSZ0vcwp7u/LvA+w2nJbIL1\n\tN0/QUUdmxfkWTHhNqgkNX5hEmYqhwUPozFR0zblfD/6+XFR7VM9yT0fZPLqYLNOmGfqAXlxY\n\tm8nWmi+lxkd/PYqQQwOq6GQwxjRFEvSc09m/YPYo9hxh7a6s8hAP88YOf2PD8oBB1r5E7KGb\n\tFv10Qss4CU/3zaiyRTExWwOJnTQdzSbtnM3S8/ZO/sL0FY/b4VLtlZzERAraxHdnPn8GgxYk\n\toPtAqoyf52RkCabL9dsXPWYQjkwG8WEUPScHDy8Uoo6imQujshG23A99iPuXcWc/5ld9mIo/\n\tEe7kN50MOXwS4vCJSv0cMkVhh77CmGUv5++E/rPcbXPLTPeRVy6SHgdDhIj7elmx2Lgo0cyh\n\tuyxyBKSuzPvb61nh5EKAGL7kPqflNw7LJkInzHqKHDNu57rVuCHEx4yxcKNB4pdE2SgyPxs9\n\t9W7Cz0q2Hd7Yu8GOXvMfQfrBiEV4q4PzidUtV6sLqVq0RMK7LEi0RiZpthwxz0IUFwRw2KS/\n\t9Kgs9LmOXYimodrV0pMxpVqcyTepmDSoWzyXNP2NL1+GuQtaTQARAQABzTBNYWNpZWogUy4g\n\tU3ptaWdpZXJvIDxtYWlsQG1hY2llai5zem1pZ2llcm8ubmFtZT7CwZQEEwEIAD4CGwMFCwkI\n\tBwIGFQoJCAsCBBYCAwECHgECF4AWIQRyeg1N257Z9gOb7O+Ef143kM4JdwUCZ7BxhgUJD0w7\n\twQAKCRCEf143kM4JdwHlD/9Ef793d6Q3WkcapGZLg1hrUg+S3d1brtJSKP6B8Ny0tt/6kjc2\n\tM8q4v0pY6rA/tksIbBw6ZVZNCoce0w3/sy358jcDldh/eYotwUCHQzXl2IZwRT2SbmEoJn9J\n\tnAOnjMCpMFRyBC1yiWzOR3XonLFNB+kWfTK3fwzKWCmpcUkI5ANrmNiDFPcsn+TzfeMV/CzT\n\tFMsqVmr+TCWl29QB3U0eFZP8Y01UiowugS0jW/B/zWYbWo2FvoOqGLRUWgQ20NBXHlV5m0qa\n\twI2Isrbos1kXSl2TDovT0Ppt+66RhV36SGA2qzLs0B9LO7/xqF4/xwmudkpabOoH5g3T20aH\n\txlB0WuTJ7FyxZGnO6NL9QTxx3t86FfkKVfTksKP0FRKujsOxGQ1JpqdazyO6k7yMFfcnxwAb\n\tMyLU6ZepXf/6LvcFFe0oXC+ZNqj7kT6+hoTkZJcxynlcxSRzRSpnS41MRHJbyQM7kjpuVdyQ\n\tBWPdBnW0bYamlsW00w5XaR+fvNr4fV0vcqB991lxD4ayBbYPz11tnjlOwqnawH1ctCy5rdBY\n\teTC6olpkmyUhrrIpTgEuxNU4GvnBK9oEEtNPC/x58AOxQuf1FhqbHYjz8D2Pyhso8TwS7NTa\n\tZ8b8o0vfsuqd3GPJKMiEhLEgu/io2KtLG10ynfh0vDBDQ7bwKoVlqC3It87AzQRaRrwiAQwA\n\txnVmJqeP9VUTISps+WbyYFYlMFfIurl7tzK74bc67KUBp+PHuDP9p4ZcJUGC3UZJP85/GlUV\n\tdE1NairYWEJQUB7bpogTuzMI825QXIB9z842HwWfP2RW5eDtJMeujzJeFaUpmeTG9snzaYxY\n\tN3r0TDKj5dZwSIThIMQpsmhH2zylkT0jH7kBPxb8IkCQ1c6wgKITwoHFjTIO0B75U7bBNSDp\n\tXUaUDvd6T3xd1Fz57ujAvKHrZfWtaNSGwLmUYQAcFvrKDGPB5Z3ggkiTtkmW3OCQbnIxGJJw\n\t/+HefYhB5/kCcpKUQ2RYcYgCZ0/WcES1xU5dnNe4i0a5gsOFSOYCpNCfTHttVxKxZZTQ/rxj\n\tXwTuToXmTI4Nehn96t25DHZ0t9L9UEJ0yxH2y8Av4rtf75K2yAXFZa8dHnQgCkyjA/gs0ujG\n\twD+Gs7dYQxP4i+rLhwBWD3mawJxLxY0vGwkG7k7npqanlsWlATHpOdqBMUiAR22hs02FikAo\n\tiXNgWTy7ABEBAAHCwXwEGAEIACYCGwwWIQRyeg1N257Z9gOb7O+Ef143kM4JdwUCZ7BxrgUJ\n\tD0w6ggAKCRCEf143kM4Jd55ED/9M47pnUYDVoaa1Xu4dVHw2h0XhBS/svPqb80YtjcBVgRp0\n\tPxLkI6afwteLsjpDgr4QbjoF868ctjqs6p/M7+VkFJNSa4hPmCayU310zEawO4EYm+jPRUIJ\n\ti87pEmygoN4ZnXvOYA9lkkbbaJkYB+8rDFSYeeSjuez0qmISbzkRVBwhGXQG5s5Oyij2eJ7f\n\tOvtjExsYkLP3NqmsODWj9aXqWGYsHPa7NpcLvHtkhtc5+SjRRLzh/NWJUtgFkqNPfhGMNwE8\n\tIsgCYA1B0Wam1zwvVgn6yRcwaCycr/SxHZAR4zZQNGyV1CA+Ph3cMiL8s49RluhiAiDqbJDx\n\tvoSNR7+hz6CXrAuFnUljMMWiSSeWDF+qSKVmUJIFHWW4s9RQofkF8/Bd6BZxIWQYxMKZm4S7\n\tdKo+5COEVOhSyYthhxNMCWDxLDuPoiGUbWBu/+8dXBusBV5fgcZ2SeQYnIvBzMj8NJ2vDU2D\n\tm/ajx6lQA/hW0zLYAew2v6WnHFnOXUlI3hv9LusUtj3XtLV2mf1FHvfYlrlI9WQsLiOE5nFN\n\tIsqJLm0TmM0i8WDnWovQHM8D0IzI/eUc4Ktbp0fVwWThP1ehdPEUKGCZflck5gvuU8yqE55r\n\tVrUwC3ocRUs4wXdUGZp67sExrfnb8QC2iXhYb+TpB8g7otkqYjL/nL8cQ8hdmg==","In-Reply-To":"<20250911135144.56586-5-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":35926,"web_url":"https://patchwork.libcamera.org/comment/35926/","msgid":"<85plbm4qq3.fsf@mzamazal-thinkpadp1gen7.tpbc.csb>","date":"2025-09-19T11:38:28","subject":"Re: [PATCH v2 4/6] libcamera: simple: Avoid incorrect arithmetic in\n\tAWB","submitter":{"id":177,"url":"https://patchwork.libcamera.org/api/people/177/","name":"Milan Zamazal","email":"mzamazal@redhat.com"},"content":"Hi Maciej,\n\nthank you for review.\n\n\"Maciej S. Szmigiero\" writes:\n\n> On 9/11/25 15:51, Milan Zamazal wrote:\n>> The R/G/B sums computed in AWB simple IPA may be zero or perhaps even\n>> negative. Let's make sure the sums are always positive, to prevent\n>\n>> division by zero or completely nonsense results.\n>> Signed-off-by: Milan Zamazal \n>> ---\n>> src/ipa/simple/algorithms/awb.cpp | 8 +++++---\n>> 1 file changed, 5 insertions(+), 3 deletions(-)\n>> diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp\n>> index cf567e894..9509129e9 100644\n>> --- a/src/ipa/simple/algorithms/awb.cpp\n>> +++ b/src/ipa/simple/algorithms/awb.cpp\n>> @@ -7,6 +7,7 @@\n>> #include \"awb.h\"\n>> +#include \n>> #include \n>> #include \n>> @@ -69,9 +70,10 @@ void Awb::process(IPAContext &context,\n>> \tconst uint64_t nPixels = std::accumulate(\n>> \t\thistogram.begin(), histogram.end(), 0);\n>> \tconst uint64_t offset = blackLevel * nPixels;\n>> -\tconst uint64_t sumR = stats->sumR_ - offset / 4;\n>> -\tconst uint64_t sumG = stats->sumG_ - offset / 2;\n>> -\tconst uint64_t sumB = stats->sumB_ - offset / 4;\n>> +\tconst uint64_t minValid = 1;\n>> +\tconst uint64_t sumR = std::max(stats->sumR_ - offset / 4, minValid);\n>> +\tconst uint64_t sumG = std::max(stats->sumG_ - offset / 2, minValid);\n>> +\tconst uint64_t sumB = std::max(stats->sumB_ - offset / 4, minValid);\n>\n> It looks like stats->sumR_ and offset are both unsigned integers so\n> I guess they won't ever go negative?\n>\n> In this case if (offset / 4) > stats->sumR_ the result will be a large\n> positive value.\n\nGood catch, I'll fix it in v3. (In theory, the sums shouldn't be below\nthe black level offset, but in practice they can.)\n\n> Thanks,\n> Macoej","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 7AEADC328C\n\tfor ;\n\tFri, 19 Sep 2025 11:38:37 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 3DA986B597;\n\tFri, 19 Sep 2025 13:38:36 +0200 (CEST)","from us-smtp-delivery-124.mimecast.com\n\t(us-smtp-delivery-124.mimecast.com [170.10.129.124])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 5EECB62C35\n\tfor ;\n\tFri, 19 Sep 2025 13:38:34 +0200 (CEST)","from mail-wr1-f72.google.com (mail-wr1-f72.google.com\n\t[209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS\n\t(version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id\n\tus-mta-133-H8FxQ8mIMduTQGzg59wabg-1; Fri, 19 Sep 2025 07:38:31 -0400","by mail-wr1-f72.google.com with SMTP id\n\tffacd0b85a97d-3ebc706ef7fso572367f8f.1\n\tfor ;\n\tFri, 19 Sep 2025 04:38:31 -0700 (PDT)","from mzamazal-thinkpadp1gen7.tpbc.csb\n\t(ip-77-48-47-2.net.vodafone.cz. 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Szmigiero\" ","Cc":"pobrn@protonmail.com, libcamera-devel@lists.libcamera.org","Subject":"Re: [PATCH v2 4/6] libcamera: simple: Avoid incorrect arithmetic in\n\tAWB","In-Reply-To":"\n\t(Maciej S. Szmigiero's message of \"Fri, 19 Sep 2025 06:15:31 +0200\")","References":"<20250911135144.56586-1-mzamazal@redhat.com>\n\t<20250911135144.56586-5-mzamazal@redhat.com>\n\t","Date":"Fri, 19 Sep 2025 13:38:28 +0200","Message-ID":"<85plbm4qq3.fsf@mzamazal-thinkpadp1gen7.tpbc.csb>","User-Agent":"Gnus/5.13 (Gnus v5.13)","MIME-Version":"1.0","X-Mimecast-Spam-Score":"0","X-Mimecast-MFC-PROC-ID":"C__ucHEsxMi9ZNsrO6jkswdRLMMg70u_36e3POYep84_1758281910","X-Mimecast-Originator":"redhat.com","Content-Type":"text/plain","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\" "}}]