将Opencv Mat返回到node.js v8

Question

How can I wrap an Opencv Mat and return it to node.js. Thank you. This is what I have.

void testFunc(const Nan::FunctionCallbackInfo<v8::Value>& info){
Mat img = imread("test.jpg");
do stuff...
return image "img"
}


void Init(v8::Local<v8::Object> exports) {  
exports->Set(Nan::New("pow").ToLocalChecked(),
             Nan::New<v8::FunctionTemplate>(testFunc)->GetFunction());
}

NODE_MODULE(pow, Init)

Answer 1

Depends on what you want to do with the Mat on the JavaScript side.

• If you just want to pass it around, you can return it as an "internal field" on some object; other C++ functions called with that object later can then retrieve it from there.
• If you want to work with it in JavaScript, you'll have to convert (eg copy pixel-by-pixel) it to some object that JavaScript understands -- a Uint8ClampedArray might serve the purpose, but it depends on your use case.
• You can also craft a JS-compatible object that uses indexed interceptors to access a Mat used as its backing store. Note, however, that crossing the API boundary is relatively slow, so for fast code, it typically makes more sense to pass lots of data at once (like the Array suggestion above), and then avoid API-crossing calls inside hot loops.