Serializing image stream using protobuf

Question

I have two programs in Ubuntu: a C++ program (TORCS game) and a python program. The C++ program always generates images. I want to transfer these real-time images into python(maybe the numpy.ndarray format). So I think that maybe using Google protobuf to serialize the image to string and send string to python client by ZMQ is a feasible method.

Question: which value type is suitable for the image(a pointer) in .proto file? In another words, which value type I should use to replace string type in the below example?

message my_image{
     repeated string image = 1
     }

This is the way I write image to memory (uint8_t* image_data):

glReadPixels(0, 0, width, height, GL_RGB, GL_UNSIGNED_BYTE, (GLvoid*)image_data);

At last, maybe there is a better way to transfer image (in the memory) to a python client?

Any suggestions are appreciated.

Answer 1

If I had to do this, I would use one of:

message image {
    int width = 1;
    int height = 2;
    bytes image_data = 3;
}

message image {
    int width = 1;
    int height = 2;
    bytes red_data = 3;
    bytes green_data = 4;
    bytes blue_data = 5;
}

Or possibly use an intermediate ScanRow message, composed either of interleaved R, G, B bytes or separated R, G, B bytes. The first version is likely going to be fastest to generate and display.