First attempt for adding threshold.

gocv/gocv.swigcxx

@@ -2,3 +2,4 @@
 
 %include "gocv_core.i"
 %include "gocv_calib3d.i"
+%include "gocv_imgproc.i"

gocv/gocv_imgproc.cpp

@@ -0,0 +1,16 @@
+#include <opencv2/opencv.hpp>
+#include <opencv2/core/core.hpp>
+#include <iostream>
+
+#include "gocv_imgproc.hpp"
+
+double GcvThreshold_(cv::Mat src, cv::Mat& dst, double thresh, double maxval, int type) {
+        std::cout << "src " << std::endl << src << std::endl;
+        std::cout << "thresh " << std::endl << thresh << std::endl;
+        std::cout << "maxval " << std::endl << maxval << std::endl;
+        std::cout << "type " << std::endl << type << std::endl;
+
+        double rtn;
+        rtn = cv::threshold(src, src, 1.0, 3.0, 0);
+        return rtn;
+}

gocv/gocv_imgproc.go

@@ -0,0 +1,17 @@
+package gocv
+
+// #cgo CXXFLAGS: -std=c++11
+// #cgo darwin pkg-config: opencv
+// #cgo linux  pkg-config: opencv
+import "C"
+import "github.com/gonum/matrix/mat64"
+
+// GcvThreshold takes a 3D column vector, and apply cv::Threshold to it.
+func GcvThreshold(src *mat64.Dense) (dst *mat64.Dense, rtn float64) {
+	gcvSrc := Mat64ToGcvMat(src)
+	gcvDst := NewGcvMat()
+	rtn = GcvThreshold_(gcvSrc, gcvDst, 1.0, 2.0, 0)
+	dst = GcvMatToMat64(gcvDst)
+
+	return dst, rtn
+}

gocv/gocv_imgproc.hpp

@@ -0,0 +1,3 @@
+#include <opencv2/opencv.hpp>
+
+double GcvThreshold_(cv::Mat src, cv::Mat& dst, double thresh, double maxval, int type);

gocv/gocv_imgproc.i

@@ -0,0 +1,5 @@
+%{
+#include "gocv_imgproc.hpp"
+%}
+
+%include "gocv_imgproc.hpp"

gocv/gocv_imgproc_test.go

@@ -0,0 +1,24 @@
+package gocv
+
+import (
+	"testing"
+
+	"github.com/gonum/matrix/mat64"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGcvThreshold(t *testing.T) {
+	rvec := mat64.NewDense(3, 1, []float64{
+		3,
+		-0.3,
+		0.2,
+	})
+	rmat, _ := GcvThreshold(rvec)
+
+	assert.InDeltaSlice(t, []float64{0.59922526, 0.57799222, -0.55394411},
+		rmat.Row(nil, 0), 1e-5)
+	assert.InDeltaSlice(t, []float64{0.20413818, 0.558743, 0.80382452},
+		rmat.Row(nil, 1), 1e-5)
+	assert.InDeltaSlice(t, []float64{0.77411672, -0.5947531, 0.21682264},
+		rmat.Row(nil, 2), 1e-5)
+}