imageProcessing: check opencv availability

* imageProcessing: guard OpenCV-dependent filters behind ALICEVISION_HAVE_OPENCV

* Apply suggestion from @fabiencastan

Co-authored-by: Fabien Castan <fabcastan@gmail.com>

* fix(imageProcessing): fix guard placement for bilateralFilter and nlmFilter OpenCV checks

The `#if ALICEVISION_HAVE_OPENCV` guards were incorrectly placed
*before* the
`if (pParams.*.enabled)` runtime checks, causing the entire block
(including
the enabled-check) to be silently skipped at compile time when OpenCV is
absent.

- Move the preprocessor guard *inside* the runtime `if` block for
  bilateralFilter
  and nlmFilter, so the enabled-check is always compiled and evaluated
- Add an `#else` branch for nlmFilter that logs an explicit error when
  OpenCV
  is unavailable and the filter is requested, instead of silently bypassing it

---------

Co-authored-by: Sylvain Maziere <sylvain.maziere@technicolor.com>
Co-authored-by: Fabien Castan <fabcastan@gmail.com>

Author: 3 people

src/software/utils/main_imageProcessing.cpp

@@ -524,11 +524,19 @@ void setupSteps(std::list<std::unique_ptr<ImageProcess>> & steps, const Processi
     }
     if (pParams.bilateralFilter.enabled)
     {
+#if ALICEVISION_IS_DEFINED(ALICEVISION_HAVE_OPENCV)
         steps.push_back(std::make_unique<BilateralFilterProcess>(pParams.bilateralFilter.distance, pParams.bilateralFilter.sigmaColor, pParams.bilateralFilter.sigmaSpace));
+#else
+        ALICEVISION_LOG_ERROR("OpenCV support is not enabled in this AliceVision build. Bilateral filter processing is unavailable and will be bypassed.");
+#endif
     }
     if (pParams.claheFilter.enabled)
     {
+#if ALICEVISION_IS_DEFINED(ALICEVISION_HAVE_OPENCV)
         steps.push_back(std::make_unique<ClaheFilterProcess>(pParams.claheFilter.tileGridSize, pParams.claheFilter.clipLimit));
+#else
+        ALICEVISION_LOG_ERROR("OpenCV support is not enabled in this AliceVision build. Clahe filter processing is unavailable and will be bypassed.");
+#endif
     }
     if (pParams.fillHoles)
     {
@@ -539,9 +547,13 @@ void setupSteps(std::list<std::unique_ptr<ImageProcess>> & steps, const Processi
         steps.push_back(std::make_unique<NoiseProcess>(ENoiseMethod_enumToString(pParams.noise.method), pParams.noise.A, pParams.noise.B, pParams.noise.mono));
     }
     if (pParams.nlmFilter.enabled)
+#if ALICEVISION_IS_DEFINED(ALICEVISION_HAVE_OPENCV)
     {
         steps.push_back(std::make_unique<NlmFilterProcess>(pParams.nlmFilter.filterStrength, pParams.nlmFilter.filterStrengthColor, pParams.nlmFilter.templateWindowSize, pParams.nlmFilter.searchWindowSize));
     }
+#else
+        ALICEVISION_LOG_ERROR("OpenCV support is not enabled in this AliceVision build. Nlm filter processing is unavailable and will be bypassed.");
+#endif
     if (pParams.applyDcpMetadata || pParams.enableColorTempProcessing)
     {
         steps.push_back(std::make_unique<ColorTemperatureProcess>(pParams.applyDcpMetadata, pParams.useDCPColorMatrixOnly, pParams.enableColorTempProcessing, pParams.correlatedColorTemperature));