C# and Python OpenCV Image Data Share (Memory Mapped File)

C#과 Python 프로그램간 이미지 데이터를 공유해 보자.

 

1) Python 프로그램 데이터를 C# 프로그램에 공유.

mmap

 

import time
import mmap
import cv2
 
frame = cv2.imread("image.jpg", cv2.IMREAD_COLOR)
h, w, c = frame.shape
buffer_size = h * w * c
 
# 3개의 4바이트(12바이트) 데이터를 위한 추가 공간 확보
#buffer_size = h * w * c + 12
 
# Open a memory-mapped file.
mm = mmap.mmap(-1, buffer_size, "Local\\MySharedMemory")
 
try:
    # 만약 3개의 4바이트 데이터를 저장하고 싶다면 아래와
    # 같이 한다.
    #mm.write(h.to_bytes(4))
    #mm.write(w.to_bytes(4))
    #mm.write(c.to_bytes(4))
 
    mm.write(frame.tobytes())
    
    # Keep the Python script running for demonstration.
    while True:
        time.sleep(1000)  # Sleep to prevent busy waiting.
finally:
    mm.close()

 

 

using OpenCvSharp;
using System.IO.MemoryMappedFiles;
using System.Runtime.InteropServices;
 
public class Program
{
    public static void Main()
    {
        int width = 396;
        int height = 495;
        int channels = 3;
 
        using (MemoryMappedFile mmf = MemoryMappedFile.OpenExisting("MySharedMemory"))
        {
            using (MemoryMappedViewAccessor accessor = mmf.CreateViewAccessor())
            {
                byte[] buffer = new byte[width * height * channels];
                accessor.ReadArray(0, buffer, 0, buffer.Length);
 
                // 만약 buffer 앞 부분에 3개의 4바이트 int 데이터가 저장되어 있다면 아래와 같이 읽는다.
                // (물론 위에서 buffer[] 생성시 12바이트의 추가 공간 확보가 필요하다)
                //int h = ((buffer[0] << 24) +  (buffer[1] << 16) + (buffer[2] << 8) + (buffer[3]));
                //Console.WriteLine(h);
                //int w = ((buffer[4] << 24) + (buffer[5] << 16) + (buffer[6] << 8) + (buffer[7]));
                //Console.WriteLine(w);
                //int c = ((buffer[8] << 24) + (buffer[9] << 16) + (buffer[10] << 8) + (buffer[11]));
                //Console.WriteLine(c);
 
                // When buffer[] represents encoded image data (ex. JPEG, PNG, etc.), you can use
                // FromImageData or ImDecode.
                //buffer = System.IO.File.ReadAllBytes("image.jpg");
                //Mat mat = Mat.FromImageData(buffer, ImreadModes.Color);                
                //Mat mat = Cv2.ImDecode(buffer, ImreadModes.Color);
 
                // When buffer[] represens pixel data (BGRBGR...) , you need to hard-code copying operation.
                //Mat mat = new Mat(height, width, MatType.CV_8UC3);
                //Mat.Indexer<Vec3b> indexer = mat.GetGenericIndexer<Vec3b>();
                //for (int y = 0; y < height; y++)
                //{
                //    for (int x = 0; x < width; x++)
                //    {
                //        int pos = y * width * channels + x * channels;
                //        byte blue = buffer[pos + 0];
                //        byte green = buffer[pos + 1];
                //        byte red = buffer[pos + 2];
                //        Vec3b newValue = new Vec3b(blue, green, red);
                //        indexer[y, x] = newValue;
                //    }
                //}
 
                // If buffer[]'s step length is equal to the Mat's, there is a more effective way.
                Mat mat = new Mat(height, width, MatType.CV_8UC3);
                int length = height * width * channels;
                Marshal.Copy(buffer, 0, mat.Data, length);
 
                Cv2.ImShow("image", mat);
                Cv2.WaitKey(0);
                Cv2.DestroyAllWindows();
            }
        }
    }
}

 

 

Python 프로그램을 먼저 실행하고 C# 프로그램을 실행한다.

 

2) C# 프로그램 데이터를 Python 프로그램에 공유.

 

using System;
using System.IO.MemoryMappedFiles;
using System.Runtime.InteropServices;
using OpenCvSharp;
 
public class Program
{
    public static void Main()
    {   
        Mat image = Cv2.ImRead("image.jpg", ImreadModes.Color);
        int width = image.Width;
        int height = image.Height;
        int channels = image.Channels();
        int buffer_size = width * height * channels;
 
        using (MemoryMappedFile mmf = MemoryMappedFile.CreateNew("MySharedMemory", buffer_size))
        {
            using (MemoryMappedViewAccessor accessor = mmf.CreateViewAccessor())
            {
                byte[] buffer = new byte[buffer_size];
                Marshal.Copy(image.Data, buffer, 0, buffer_size);
                accessor.WriteArray<byte>(0, buffer, 0, buffer_size);
            }
            
            Console.WriteLine("waiting...");
            Console.ReadLine();
        }        
    }
}

 

 

import mmap
import numpy as np
import cv2
 
height = 495
width = 396
channels = 3
buffer_size = height * width * channels
 
mm = mmap.mmap(-1, buffer_size, "Local\\MySharedMemory")
 
try:    
    buffer = mm.read(buffer_size)
    image_arr = np.frombuffer(buffer, np.ubyte)
    image = image_arr.reshape(height, width, channels)
    
    cv2.imshow("image", image)
    cv2.waitKey(0)
finally:
    mm.close()
    cv2.destroyAllWindows()

 

결과는 같다.

 

※ 참고

2025.02.23 - [OpenCV] - C and Python OpenCV Image Data Share (Memory Mapped File)