From cff796a4b7bfe72530e43ecc3e9288fc0dc57dee Mon Sep 17 00:00:00 2001
From: Joao Carreira <jfmcarreira@gmail.com>
Date: Tue, 12 Mar 2019 02:18:11 +0000
Subject: [PATCH] Add different interpolation techniques to the ERP to NxN
 conversion

---
 modules/ThreeSixtyDownsampling.cpp | 36 +++++++++++++++++++++++++-----
 modules/ThreeSixtyDownsampling.h   |  3 ++-
 2 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/modules/ThreeSixtyDownsampling.cpp b/modules/ThreeSixtyDownsampling.cpp
index 098e76b..a79a207 100644
--- a/modules/ThreeSixtyDownsampling.cpp
+++ b/modules/ThreeSixtyDownsampling.cpp
@@ -44,11 +44,19 @@ ThreeSixtyDownsampling::ThreeSixtyDownsampling()
   m_uiNumberOfFrames = 1;
   m_uiModuleRequirements = CLP_MODULE_REQUIRES_SKIP_WHILE_PLAY | CLP_MODULE_REQUIRES_OPTIONS;
 
-  m_cModuleOptions.addOptions() /**/
-      ( "Downsampling", m_bDownsampling, "ERP to NxN [true]" );
+  m_cModuleOptions.addOptions()                                /**/
+      ( "Downsampling", m_bDownsampling, "ERP to NxN [true]" ) /**/
+      ( "Interpolation", m_iInterpolation, "Interpolation method (1-5) [1]" );
+
+  //    INTER_NEAREST - a nearest-neighbor interpolation
+  //    INTER_LINEAR - a bilinear interpolation (used by default)
+  //    INTER_AREA - resampling using pixel area relation. It may be a preferred method for image decimation, as it gives moire’-free results. But when the image is zoomed, it is similar to the INTER_NEAREST method.
+  //    INTER_CUBIC - a bicubic interpolation over 4x4 pixel neighborhood
+  //    INTER_LANCZOS4 - a Lanczos interpolation over 8x8 pixel neighborhood
+  m_bDownsampling = true;
+  m_iInterpolation = 1;
 
   m_pcOutputFrame = NULL;
-  m_bDownsampling = true;
 }
 
 bool ThreeSixtyDownsampling::create( std::vector<CalypFrame*> apcFrameList )
@@ -56,6 +64,24 @@ bool ThreeSixtyDownsampling::create( std::vector<CalypFrame*> apcFrameList )
   _BASIC_MODULE_API_2_CHECK_
   m_pcOutputFrame = new CalypFrame( apcFrameList[0]->getWidth(), apcFrameList[0]->getHeight(), CLP_GRAY );
   m_isOdd = !( m_pcOutputFrame->getHeight() % 2 );
+
+  switch( m_iInterpolation )
+  {
+  case 2:
+    m_iInterpolation = cv::INTER_LINEAR;
+    break;
+  case 3:
+    m_iInterpolation = cv::INTER_AREA;
+    break;
+  case 4:
+    m_iInterpolation = cv::INTER_CUBIC;
+    break;
+  case 5:
+    m_iInterpolation = cv::INTER_LANCZOS4;
+    break;
+  default:
+    m_iInterpolation = cv::INTER_NEAREST;
+  }
   return true;
 }
 
@@ -92,14 +118,14 @@ CalypFrame* ThreeSixtyDownsampling::process( std::vector<CalypFrame*> apcFrameLi
       // resize
       if( m_bDownsampling )
       {
-        cv::resize( cvIn.row( ypos ), cvDownsample, cvDownsample.size() );
+        cv::resize( cvIn.row( ypos ), cvDownsample, cvDownsample.size(), 0, 0, m_iInterpolation );
         cvOutput = cvDownsample;
       }
       else
       {
         Mat cvauxin = cvIn.row( ypos ).colRange( xpos, xpos + lineWidth );
         cvauxin.copyTo( cvDownsample );
-        cv::resize( cvDownsample, cvUpsample, cvUpsample.size() );
+        cv::resize( cvDownsample, cvUpsample, cvUpsample.size(), 0, 0, m_iInterpolation );
         cvOutput = cvUpsample;
       }
 
diff --git a/modules/ThreeSixtyDownsampling.h b/modules/ThreeSixtyDownsampling.h
index 0319f39..c7d838e 100644
--- a/modules/ThreeSixtyDownsampling.h
+++ b/modules/ThreeSixtyDownsampling.h
@@ -32,8 +32,9 @@ class ThreeSixtyDownsampling : public CalypModuleIf
 {
   REGISTER_CLASS_FACTORY( ThreeSixtyDownsampling )
 private:
-  bool m_bDownsampling;
   bool m_isOdd;
+  bool m_bDownsampling;
+  int m_iInterpolation;
 
 public:
   ThreeSixtyDownsampling();