OpenCV DNN throws exception with Mask RCNN(Resnet 50) model

[qianyunw]

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System information (version)

• OpenCV => 4.0.0
• Operating System / Platform => Ubuntu 16.04 64 Bit
• Compiler => gcc (5.4)
• Cuda 9.0
• cudnn 7

Detailed description

I trained a Mask RCNN model(with Resnet50 backbone) by using a Tensorflow object detection API. I try to test the model with a C++ (OpenCV DNN) application and a c++ file(mask_rcnn.cpp)(https://github.com/spmallick/learnopencv/tree/master/Mask-RCNN), but the getConstBlob always drop this exception

~/mask-rcnn-cv$ ./mask_rcnn.out --image='/home/wangqianyun/mask-rcnn-cv/cars.jpg' ./mask_rcnn.outterminate called after throwing an instance of 'cv::Exception'
what(): OpenCV(4.0.0) /home/wangqianyun/opencv/modules/dnn/src/tensorflow/tf_importer.cpp:535: error: (-2:Unspecified error) Input [FirstStageFeatureExtractor/resnet_v1_50/resnet_v1_50/block3/unit_1/bottleneck_v1/conv2/Conv2D/paddings] for node [FirstStageFeatureExtractor/resnet_v1_50/resnet_v1_50/block3/unit_1/bottleneck_v1/conv2/SpaceToBatchND] not found in function 'getConstBlob'

Steps to reproduce

1. similiar to tf_text_graph_faster_rcnn.py - Assertion error #13237, modify a pipeline.config file:
   replace

height_stride: 8
weight_stride: 8
to
height_stride: 16
weight_stride: 16
```

2. use tf_text_graph_mask_rcnn.py() to produce .pbtxt from .pb and .config

3. compile and run

g++ -std=c++11 -ggdb mask_rcnn.cpp -o mask_rcnn.out pkg-config --cflags --libs /home/wangqianyun/opencv/build/unix-install/opencv4.pc
(cv) wangqianyun@wangqianyun-ThinkCentre-E73:~/mask-rcnn-cv$ ./mask_rcnn.out --image='/home/wangqianyun/mask-rcnn-cv/cars.jpg' ./mask_rcnn.out.cpp
//
```