From 5ef06b0e921f2c3dd3f1c33f92845b14eddab123 Mon Sep 17 00:00:00 2001
From: Cris Luengo <cris.l.luengo@gmail.com>
Date: Mon, 13 May 2024 09:39:37 -0600
Subject: [PATCH] Real-to-Complex Fourier transform of size 2 failed. Fixes
 #158.

---
 src/linear/gauss.cpp      | 4 +++-
 src/transform/fourier.cpp | 8 +++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/linear/gauss.cpp b/src/linear/gauss.cpp
index f6b3b740..397c644e 100644
--- a/src/linear/gauss.cpp
+++ b/src/linear/gauss.cpp
@@ -389,7 +389,7 @@ void GaussFT(
       bool reuseInFT = false;
       if( inSpatial ) {
          real = !in.DataType().IsComplex();
-         inFT = FourierTransform( in );
+         DIP_STACK_TRACE_THIS( inFT = FourierTransform( in ));
          reuseInFT = true;
       } else {
          inFT = in;
@@ -417,6 +417,7 @@ void GaussFT(
          DIP_STACK_TRACE_THIS( FourierTransform( outFT, out, options ));
       }
    } else {
+      DIP_START_STACK_TRACE
       if( inSpatial == outSpatial ) {
          out = in;
       } else if( inSpatial ) {
@@ -424,6 +425,7 @@ void GaussFT(
       } else {
          FourierTransform( in, out, { S::INVERSE } );
       }
+      DIP_END_STACK_TRACE
    }
 }
 
diff --git a/src/transform/fourier.cpp b/src/transform/fourier.cpp
index bf998053..46381ee3 100644
--- a/src/transform/fourier.cpp
+++ b/src/transform/fourier.cpp
@@ -396,6 +396,9 @@ void DFT_R2C_1D_finalize(
    DIP_ASSERT( !process[ dimension ] ); // the R2C process dimension should not be a C2C process dimension
    // Input: pixels 0 to size/2 are set
    dip::uint size = img.Size( dimension );
+   if( size <= 2 ) {
+      return;  // We've got nothing to do here
+   }
    RangeArray leftWindow( nDims );
    if( !( size & 1u )) {
       // even size: pixels 0 and size/2 stay where they are
@@ -540,7 +543,10 @@ void FourierTransform(
          } else {
             DIP_THROW_IF( outSize[ ii ] > maximumDFTSize, "Image size too large for DFT algorithm" );
          }
-         if( !process[ optimalDimension ] || ( std::abs( out.Stride( ii )) < std::abs( out.Stride( optimalDimension )))) {
+         if( !process[ optimalDimension ] || (
+               ( outSize[ ii ] > 2 ) &&
+               ( std::abs( in.Stride( ii )) < std::abs( in.Stride( optimalDimension )))
+         )) {
             optimalDimension = ii;
          }
          scale /= static_cast< dfloat >( outSize[ ii ] );