[sift] removed support for a narrow Gaussian filter width computation

* Soft failing if someone uses the old parameter --gauss-mode=opencv

---------

Co-authored-by: Carsten Griwodz <[email protected]>

Author: griwodz

CHANGES.md

@@ -20,7 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Removed
 
 - Removed option to create top level of every octave from input image [PR](https://github.com/alicevision/popsift/pull/178)
-- Removed option to compute very narrow Gaussian filters called opencv [PR]
+- Removed option to compute very narrow Gaussian filters called opencv [PR](https://github.com/alicevision/popsift/pull/179)
 
 ## [0.10.0] - 2025-10-14
 

src/popsift/sift_conf.cu

@@ -115,7 +115,10 @@ void Config::setGaussMode( const std::string& m )
         setGaussMode( Config::Fixed9 );
     else if( m == "fixed15" )
         setGaussMode( Config::Fixed15 );
-    else
+    else if( m == "opencv" ) {
+        POP_WARN( string("Gauss mode 'opencv' has been deprecated. Using mode vlfeat instead.\n") );
+        setGaussMode( Config::VLFeat_Compute );
+    } else
         POP_FATAL( string("Bad Gauss mode.\n") + getGaussModeUsage() );
 }