What is the process of MNN :: CV :: ImageProcess module processing images?

[TCBocean]

My expected processing flow is to first reduce the picture to the input size of the network, then divide by 255.0, subtract mean, and divide by std.
My code is:

    auto input = interpreter->getSessionInput(session, nullptr);
    int width = 1436;
    int height = 1920;
    MNN::CV::ImageProcess::Config config_data;
    config_data.filterType = MNN::CV::BILINEAR;
    const float mean_vals[3] = {140.97361f, 129.48639f, 125.60532f};
    const float norm_vals[3] = {68.57847f, 66.457595f, 65.706699f};
    ::memcpy(config_data.mean, mean_vals, sizeof(mean_vals));
    ::memcpy(config_data.normal, norm_vals, sizeof(norm_vals));
    config_data.sourceFormat = MNN::CV::RGB;
    config_data.destFormat = MNN::CV::ImageFormat::RGB;
    std::unique_ptr<MNN::CV::ImageProcess> process(MNN::CV::ImageProcess::create(config_data));
    MNN::CV::Matrix matrix;
    matrix.setIdentity();
    matrix.postScale(width/352.0, height/352.0);
    process->setMatrix(matrix);

    jbyte *bufferData = env->GetByteArrayElements(jbufferData, NULL);
    if (bufferData == NULL) {
        MNN_ERROR("Error Buffer Null!\n");
        return JNI_FALSE;
    }
    process->convert((const unsigned char *)bufferData, width, height, 0, input); 
    env->ReleaseByteArrayElements(jbufferData, bufferData, 0);

The mean and std here are the result of multiplying by 255, because my mean and std are obtained in the range of 0 ~ 1.
I am not sure if the processing flow of MNN :: CV :: ImageProcess module is divided by 255.

    auto inputtensor = new MNN::Tensor(input, MNN::Tensor::TENSORFLOW);
    float * temp = inputtensor->host<float>();
    jbyte *bufferData = env->GetByteArrayElements(jbufferData, NULL);
    if (bufferData == NULL) {
        MNN_ERROR("Error Buffer Null!\n");
        return JNI_FALSE;
    }
    detector_component->normalization_source_image((uint8_t const*)bufferData, temp,3, 0, 1);
    input->copyFromHostTensor(inputtensor);

I used the interface I wrote and processed it according to the process I mentioned before, and I can get the correct results.
So I guess that my code can't be executed according to my expectations. Can someone teach me how to configure MNN :: CV :: ImageProcess module before resize, then reduce maen, and then divide std?
Thank you very much~

[jxt1234]

You should div normal by 255
68.57847f, 66.457595f, 65.706699f -> (68.57847f, 66.457595f, 65.706699f) / 255.0f

[TCBocean]

@jxt1234
Do you mean the processing flow of MNN::CV::ImageProcess module is as follows?
((img - mean) / 255) / norm

[jxt1234]

no. It's dst = (img - mean) * normal

[TCBocean]

I understand