dnn with custom layer: Assertion failed !empty() in function 'forward'

asked 2020-11-21 16:46:45 -0500

Joanne gravatar image

updated 2020-11-22 10:53:01 -0500

System information (version)

OpenCV => 4.5.0

Operating System / Platform => iOS 14.1

Compiler => :Xcode 12.1 (12A7403)

I'm getting this error:

libc++abi.dylib: terminating with uncaught exception of type cv::Exception: OpenCV(4.5.0) /Volumes/build-storage/build/master_iOS-mac/opencv/modules/dnn/src/dnn.cpp:3977: error: (-215:Assertion failed) !empty() in function 'forward'

This is triggered by net.forward() - see below please.

using namespace cv;
using namespace std;

class CropLayer : public cv::dnn::Layer


    CropLayer(const cv::dnn::LayerParams &params) : Layer(params) {}

static cv::Ptr<cv::dnn::Layer> create(cv::dnn::LayerParams& params) {
    return cv::Ptr<cv::dnn::Layer>(new CropLayer(params));

virtual bool getMemoryShapes(const std::vector<std::vector<int> > &inputs,
                             const int requiredOutputs,
                             std::vector<std::vector<int> > &outputs,
                             std::vector<std::vector<int> > &internals) const CV_OVERRIDE {
    CV_UNUSED(requiredOutputs); CV_UNUSED(internals);
    std::vector<int> outShape(4);
    outShape[0] = inputs[0][0];  // batch size
    outShape[1] = inputs[0][1];  // number of channels
    outShape[2] = inputs[1][2];
    outShape[3] = inputs[1][3];
    outputs.assign(1, outShape);
    return false;

virtual void forward(cv::InputArrayOfArrays inputs_arr,
                     cv::OutputArrayOfArrays outputs_arr,
                     cv::OutputArrayOfArrays internals_arr) CV_OVERRIDE {
    std::vector<cv::Mat> inputs, outputs;
    cv::Mat& inp = inputs[0];
    cv::Mat& out = outputs[0];
    int ystart = (inp.size[2] - out.size[2]) / 2;
    int xstart = (inp.size[3] - out.size[3]) / 2;
    int yend = ystart + out.size[2];
    int xend = xstart + out.size[3];
    const int batchSize = inp.size[0];
    const int numChannels = inp.size[1];
    const int height = out.size[2];
    const int width = out.size[3];
    int sz[] = { (int)batchSize, numChannels, height, width };
    out.create(4, sz, CV_32F);
    for(int i=0; i<batchSize; i++) {
        for(int j=0; j<numChannels; j++) {
            cv::Mat plane(inp.size[2], inp.size[3], CV_32F, inp.ptr<float>(i,j));
            cv::Mat crop = plane(cv::Range(ystart,yend), cv::Range(xstart,xend));
            cv::Mat targ(height, width, CV_32F, out.ptr<float>(i,j));
} };

cv::dnn::Net net;
net = cv::dnn::readNet("hed_pretrained_bsds.caffemodel" ,"deploy.prototxt");
void process(cv::Mat& img) {
  cv::Size reso(500,500);
  cv::Mat blob = cv::dnn::blobFromImage(img, 1.0, reso, cv::Scalar(104.00698793, 116.66876762, 122.67891434), false, false);
  cv::Mat out = net.forward(); //Runtime ERROR here 
  cv::resize(out.reshape(1, reso.height), out, img.size());
  img = out;

model: https://firebasestorage.googleapis.co... deploy.prototxt: https://firebasestorage.googleapis.co...

Thank you

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where and how are you calling this ?

cv::dnn::Net net;
net = cv::dnn::readNet("hed_pretrained_bsds.caffemodel" ,"deploy.prototxt");

the error complains, that your net does not have any layers

berak gravatar imageberak ( 2020-11-22 04:32:10 -0500 )edit

@berak - that code is called when an object of the class that the process() method belongs to is initialized. It runs before anyone can call process().

Joanne gravatar imageJoanne ( 2020-11-22 10:51:28 -0500 )edit

btw, if I call CV_DNN_REGISTER_LAYER_CLASS(Crop, CropLayer); twice, then the second time it complains that the layer is already registered.

Joanne gravatar imageJoanne ( 2020-11-22 12:14:39 -0500 )edit

^^ yep, that's expected behaviour

berak gravatar imageberak ( 2020-11-22 12:21:55 -0500 )edit

Right, and that would mean that the layer was registered successfully. Why is empty() true then?

Joanne gravatar imageJoanne ( 2020-11-22 14:59:03 -0500 )edit

registering a layer does not mean, your network contains any instances of anything

berak gravatar imageberak ( 2020-11-22 15:06:57 -0500 )edit

You think the model is wrong then? Sorry, I'm a newbie when it comes to ML. My understanding was that the network would use the registered layer. I've looked into the prototxt file and Crop is referenced there.

Joanne gravatar imageJoanne ( 2020-11-22 15:25:13 -0500 )edit

no, it looks more, like it wasn't correctly loaded.

unfortunately now, we cannot reproduce it, since your code is incomplete

berak gravatar imageberak ( 2020-11-23 02:32:58 -0500 )edit