c# - 优化从 opencv mat/Array 到 OnnxRuntime Tensor 的转换？

Question

我正在使用 ONNXRuntime 来推断 UNet 模型，作为预处理的一部分，我必须将 EMGU OpenCV 矩阵转换为 OnnxRuntime.Tensor。

我使用两个嵌套的 for 循环实现了它，不幸的是速度很慢:

            var data = new DenseTensor<float>(new[] { 1, 3, WIDTH, HEIGHT});

            for (int y = 0; y < HEIGHT; y++)
            {
                for (int x = 0; x < WIDTH; x++)
                {
                    data[0, 0, x, y] = image.GetValue(2, y, x)/255.0;
                    data[0, 1, x, y] = image.GetValue(1, y, x)/255.0;
                    data[0, 2, x, y] = image.GetValue(0, y, x)/255.0;
                }
            } 

然后我发现有一个方法可以将Array转换为DenseTensor。我想按如下方式使用此方法:

        var imgToPredictFloat = new Mat(image.Height, image.Width, DepthType.Cv32F, 3);
        image.ConvertTo(imgToPredictFloat, DepthType.Cv32F, 1/255.0);
        CvInvoke.CvtColor(imgToPredictFloat, imgToPredictFloat, ColorConversion.Bgra2Rgb);

        var data = image.GetData().ToTensor<float>;
        var reshaped = data.Reshape(new int[] { 1, 3, WIDTH, HEIGHT});

这将极大地提高性能，但是输出张量的布局不正确(与 for 循环相同)并且模型显然无法工作。有什么建议如何将数组 reshape 为正确的布局吗？

代码中还执行了将 int 0-255 转换为 float 0-1 以及将 BGR 布局转换为 RGB 布局。

Answer 1

这就是我将 cv::Mat 与 ONNX Runtime (C++) 结合使用的方式:

const wchar_t* model_path = L"C:/data/DNN/ONNX/ResNet/resnet152v2/resnet152-v2-7.onnx";

printf("Using Onnxruntime C++ API\n");
Ort::Session session(env, model_path, session_options);


//*************************************************************************
// print model input layer (node names, types, shape etc.)
Ort::AllocatorWithDefaultOptions allocator;

size_t num_output_nodes = session.GetOutputCount();
std::vector<char*> outputNames;
for (size_t i = 0; i < num_output_nodes; ++i)
{
    char* name = session.GetOutputName(i, allocator);
    std::cout << "output: " << name << std::endl;
    outputNames.push_back(name);
}


// print number of model input nodes
size_t num_input_nodes = session.GetInputCount();
std::vector<const char*> input_node_names(num_input_nodes);
std::vector<int64_t> input_node_dims;  // simplify... this model has only 1 input node {1, 3, 224, 224}.
                                       // Otherwise need vector<vector<>>

printf("Number of inputs = %zu\n", num_input_nodes);

// iterate over all input nodes
for (int i = 0; i < num_input_nodes; i++) {
    // print input node names
    char* input_name = session.GetInputName(i, allocator);
    printf("Input %d : name=%s\n", i, input_name);
    input_node_names[i] = input_name;

    // print input node types
    Ort::TypeInfo type_info = session.GetInputTypeInfo(i);
    auto tensor_info = type_info.GetTensorTypeAndShapeInfo();

    ONNXTensorElementDataType type = tensor_info.GetElementType();
    printf("Input %d : type=%d\n", i, type);

    // print input shapes/dims
    input_node_dims = tensor_info.GetShape();
    printf("Input %d : num_dims=%zu\n", i, input_node_dims.size());
    for (int j = 0; j < input_node_dims.size(); j++)
        printf("Input %d : dim %d=%jd\n", i, j, input_node_dims[j]);
}


cv::Size dnnInputSize;
cv::Scalar mean;
cv::Scalar std;
bool rgb = true;

//cv::Mat inputImage = cv::imread("C:/TestImages/kitten_01.jpg");
cv::Mat inputImage = cv::imread("C:/TestImages/slug_01.jpg");

rgb = true;
dnnInputSize = cv::Size(224, 224);
mean[0] = 0.485;
mean[1] = 0.456;
mean[2] = 0.406;
std[0] = 0.229;
std[1] = 0.224;
std[2] = 0.225;

cv::Mat blob;
// ONNX: (N x 3 x H x W)
cv::dnn::blobFromImage(inputImage, blob, 1.0 / 255.0, dnnInputSize, mean, rgb, false);

size_t input_tensor_size = blob.total();

std::vector<float> input_tensor_values(input_tensor_size);
for (size_t i = 0; i < input_tensor_size; ++i)
{
    input_tensor_values[i] = blob.at<float>(i);
}
std::vector<const char*> output_node_names = { outputNames.front() };

// create input tensor object from data values
auto memory_info = Ort::MemoryInfo::CreateCpu(OrtArenaAllocator, OrtMemTypeDefault);
Ort::Value input_tensor = Ort::Value::CreateTensor<float>(memory_info, input_tensor_values.data(), input_tensor_size, input_node_dims.data(), 4);
assert(input_tensor.IsTensor());

// score model & input tensor, get back output tensor
auto output_tensors = session.Run(Ort::RunOptions{ nullptr }, input_node_names.data(), &input_tensor, 1, output_node_names.data(), 1);
assert(output_tensors.size() == 1 && output_tensors.front().IsTensor());

// Get pointer to output tensor float values
float* floatarr = output_tensors.front().GetTensorMutableData<float>();
assert(abs(floatarr[0] - 0.000045) < 1e-6);

cv::Mat1f result = cv::Mat1f(1000, 1, floatarr);

cv::Point classIdPoint;
double confidence = 0;
minMaxLoc(result, 0, &confidence, 0, &classIdPoint);
int classId = classIdPoint.y;
std::cout << "confidence: " << confidence << std::endl;
std::cout << "class: " << classId << std::endl;

您需要的实际转换部分是恕我直言(根据您的网络调整大小和平均值/标准差):

cv::Mat inputImage = cv::imread("C:/TestImages/slug_01.jpg");

rgb = true;
dnnInputSize = cv::Size(224, 224);
mean[0] = 0.485;
mean[1] = 0.456;
mean[2] = 0.406;
std[0] = 0.229;
std[1] = 0.224;
std[2] = 0.225;

cv::Mat blob;
// ONNX: (N x 3 x H x W)
cv::dnn::blobFromImage(inputImage, blob, 1.0 / 255.0, dnnInputSize, mean, rgb, false);