Update link INRIA, improve style RecursiveGaussianImageFilter and RecursiveSeparableImageFilter#5687
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thewtex merged 6 commits intoInsightSoftwareConsortium:mainfrom Dec 15, 2025
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Following MISRA-C++ Rule "If a member function can be made static then it shall be made static" and Clang-Tidy `readability-convert-member-functions-to-static`, https://clang.llvm.org/extra/clang-tidy/checks/readability/convert-member-functions-to-static.html
Following C++ Core Guidelines, Jul 8, 2025, "Don’t define a default constructor that only initializes data members; use default member initializers instead", https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c45-dont-define-a-default-constructor-that-only-initializes-data-members-use-default-member-initializers-instead
Removed the member initializer list from the default-constructor, used default member initializers in the class definition instead.
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N-Dekker
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Dec 14, 2025
Comment on lines
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| A1[0] = static_cast<ScalarRealType>(1.3530); | ||
| B1[0] = static_cast<ScalarRealType>(1.8151); | ||
| W1 = static_cast<ScalarRealType>(0.6681); | ||
| L1 = static_cast<ScalarRealType>(-1.3932); | ||
| A2[0] = static_cast<ScalarRealType>(-0.3531); | ||
| B2[0] = static_cast<ScalarRealType>(0.0902); | ||
| W2 = static_cast<ScalarRealType>(2.0787); | ||
| L2 = static_cast<ScalarRealType>(-1.3732); | ||
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| A1[1] = static_cast<ScalarRealType>(-0.6724); | ||
| B1[1] = static_cast<ScalarRealType>(-3.4327); | ||
| A2[1] = static_cast<ScalarRealType>(0.6724); | ||
| B2[1] = static_cast<ScalarRealType>(0.6100); | ||
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| A1[2] = static_cast<ScalarRealType>(-1.3563); | ||
| B1[2] = static_cast<ScalarRealType>(5.2318); | ||
| A2[2] = static_cast<ScalarRealType>(0.3446); | ||
| B2[2] = static_cast<ScalarRealType>(-2.2355); |
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For the record, it appears that these "magic numbers" were originally introduced with commit ef006d2, Luis Ibanez, Jan 17, 2005. They are also presented in Table 3. "Proposed new parameters in the approximation of the Gaussian and its derivatives...", in "Improving Deriche-style Recursive Gaussian Filters", by Gunnar Farnebäck & Carl-Fredrik Westin, Nov 30 2006.
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Is it worth documenting in the code the source of these numbers?
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@blowekamp Good suggestion, thanks! As follows?
// Parameters of exponential series.
// These numbers correspond with Table 3. "Proposed new parameters in the approximation of the Gaussian and its
// derivatives..." of "Improving Deriche-style Recursive Gaussian Filters" [farneback2006].I hope it's clear enough that [farneback2006] refers to our bib entry at
ITK/Documentation/Doxygen/doxygen.bib
Lines 374 to 384 in 53158e3
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Yes, it is to me as it's in the class documentation.
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To be added to a follow-up 😃
Aims to clarify the code of `RecursiveSeparableImageFilter::FilterDataArray`.
The FTP site ftp.inria.fr appears to be replaced with https://inria.hal.science
Removed unnecessary `static_cast<ScalarRealType>`s.
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blowekamp
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Dec 15, 2025
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The style improvements look good to me.
Comment on lines
-93
to
-110
| A1[0] = static_cast<ScalarRealType>(1.3530); | ||
| B1[0] = static_cast<ScalarRealType>(1.8151); | ||
| W1 = static_cast<ScalarRealType>(0.6681); | ||
| L1 = static_cast<ScalarRealType>(-1.3932); | ||
| A2[0] = static_cast<ScalarRealType>(-0.3531); | ||
| B2[0] = static_cast<ScalarRealType>(0.0902); | ||
| W2 = static_cast<ScalarRealType>(2.0787); | ||
| L2 = static_cast<ScalarRealType>(-1.3732); | ||
|
|
||
| A1[1] = static_cast<ScalarRealType>(-0.6724); | ||
| B1[1] = static_cast<ScalarRealType>(-3.4327); | ||
| A2[1] = static_cast<ScalarRealType>(0.6724); | ||
| B2[1] = static_cast<ScalarRealType>(0.6100); | ||
|
|
||
| A1[2] = static_cast<ScalarRealType>(-1.3563); | ||
| B1[2] = static_cast<ScalarRealType>(5.2318); | ||
| A2[2] = static_cast<ScalarRealType>(0.3446); | ||
| B2[2] = static_cast<ScalarRealType>(-2.2355); |
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Is it worth documenting in the code the source of these numbers?
thewtex
approved these changes
Dec 15, 2025
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The INRIA report by Rachid Deriche, "Recursively Implementing The Gaussian and Its Derivatives", 1993, appears to be moved to https://inria.hal.science/inria-00074778
This pull request also proposes various style improvements to
RecursiveGaussianImageFilterand its base classRecursiveSeparableImageFilter.