Fixed testing for imreadmulti on OpenCV < 3, added distanceTransform function to imgproc module.

src/Constants.cc

@@ -4,6 +4,9 @@
 #define CONST(C) \
   obj->Set(Nan::New<String>(#C).ToLocalChecked(), Nan::New<Integer>(C));
 
+#define CONST_INT(C) \
+  obj->Set(Nan::New<String>(#C).ToLocalChecked(), Nan::New<Integer>((int)C));
+
 #define CONST_DOUBLE(C) \
   obj->Set(Nan::New<String>(#C).ToLocalChecked(), Nan::New<Number>(C));
 
@@ -90,6 +93,14 @@ void Constants::Init(Local<Object> target) {
   CONST_ENUM(RETR_CCOMP);
   CONST_ENUM(RETR_TREE);
 
+  CONST_INT(CV_DIST_C);
+  CONST_INT(CV_DIST_L1);
+  CONST_INT(CV_DIST_L2);
+
+  CONST_INT(CV_DIST_MASK_3);
+  CONST_INT(CV_DIST_MASK_5);
+  CONST_INT(CV_DIST_MASK_PRECISE);
+
   target->Set(Nan::New("Constants").ToLocalChecked(), obj);
 }
 

src/ImgProc.cc

@@ -9,11 +9,44 @@ void ImgProc::Init(Local<Object> target) {
   Nan::SetMethod(obj, "undistort", Undistort);
   Nan::SetMethod(obj, "initUndistortRectifyMap", InitUndistortRectifyMap);
   Nan::SetMethod(obj, "remap", Remap);
+  Nan::SetMethod(obj, "distanceTransform", DistanceTransform);
   Nan::SetMethod(obj, "getStructuringElement", GetStructuringElement);
 
   target->Set(Nan::New("imgproc").ToLocalChecked(), obj);
 }
 
+// cv::distanceTransform
+NAN_METHOD(ImgProc::DistanceTransform) {
+  Nan::EscapableHandleScope scope;
+
+  try {
+    // Arg 0 is the image
+    Matrix* m0 = Nan::ObjectWrap::Unwrap<Matrix>(info[0]->ToObject());
+    cv::Mat inputImage = m0->mat;
+
+    // Arg 1 is the distance type (CV_DIST_L1, CV_DIST_L2, etc.)
+    int distType = info[1]->IntegerValue();;
+
+    // Make a mat to hold the result image
+    cv::Mat outputImage;
+
+    // Perform distance transform
+    cv::distanceTransform(inputImage, outputImage, distType, 0);
+
+    // Wrap the output image
+    Local<Object> outMatrixWrap = Nan::New(Matrix::constructor)->GetFunction()->NewInstance();
+    Matrix *outMatrix = Nan::ObjectWrap::Unwrap<Matrix>(outMatrixWrap);
+    outMatrix->mat = outputImage;
+
+    // Return the output image
+    info.GetReturnValue().Set(outMatrixWrap);
+  } catch (cv::Exception &e) {
+    const char *err_msg = e.what();
+    Nan::ThrowError(err_msg);
+    return;
+  }
+}
+
 // cv::undistort
 NAN_METHOD(ImgProc::Undistort) {
   Nan::EscapableHandleScope scope;

src/ImgProc.h

@@ -9,6 +9,7 @@
 class ImgProc: public Nan::ObjectWrap {
 public:
   static void Init(Local<Object> target);
+  static NAN_METHOD(DistanceTransform);
   static NAN_METHOD(Undistort);
   static NAN_METHOD(InitUndistortRectifyMap);
   static NAN_METHOD(Remap);

src/OpenCV.cc

@@ -68,6 +68,7 @@ NAN_METHOD(OpenCV::ReadImage) {
   return;
 }
 
+#if CV_MAJOR_VERSION >= 3
 NAN_METHOD(OpenCV::ReadImageMulti) {
   Nan::EscapableHandleScope scope;
 
@@ -111,3 +112,9 @@ NAN_METHOD(OpenCV::ReadImageMulti) {
 
   return;
 }
+#else
+NAN_METHOD(OpenCV::ReadImageMulti) {
+  info.GetReturnValue().Set(Nan::New<Boolean>(false));
+  return;
+}
+#endif

test/unit.js

@@ -217,6 +217,7 @@ test("Image read from file", function(assert){
 })
 
 test("Multi-page image read from file", function(assert){
+  if (parseInt(cv.version) >= 3) {
     cv.readImageMulti("./examples/files/multipage.tif", function(err, imgs){
       assert.ok(imgs);
       assert.equal(imgs.length, 10);
@@ -229,6 +230,22 @@ test("Multi-page image read from file", function(assert){
       }
       assert.end();
     })
+  } else {
+    console.log(cv.Constants);
+    assert.equal(cv.readImageMulti("./examples/files/multipage.tif"), false);
+    assert.end();
+  }
+})
+
+test("Distance transform", function(assert){
+  cv.readImage("./examples/files/distanceTransform.png", function(err, img){
+    assert.ok(img);
+
+    // 50px image with single black pixel on right side
+    var result = cv.imgproc.distanceTransform(img, cv.Constants.CV_DIST_L2, cv.Constants.CV_DIST_MASK_PRECISE);
+    assert.equal(result.get(0,0), 49);
+    assert.end();
+  })
 })
 
 test("read Image from buffer", function(assert){