python cv2 img encode and call clib

shm_input.c

int shm_send_pic(char* buf,int size)
{
    if((buf == NULL) || (size <= 0))
    {
        printf("para error\n");
        return -1;
    }

    int shmid = shmget(SHM_KEY,SHM_SIZE,IPC_CREAT|0664);
    if(-1 == shmid)
    {
        printf("shmget fail\n");
        return -1;
    }

    void* ptr = shmat(shmid,NULL,0);
    if(((void*)-1) == ptr)
    {
        printf("shmat fail\n");
        return -1;
    }

    int* pi = ptr;
    *pi = size;

    memcpy(ptr+sizeof(int),buf,size);

    return 0;
}

gcc -o libc_send_pic.so -shared -fPIC shm_input.c

 

pytest.py

#!/usr/bin/python3

import cv2
import numpy as np
import ctypes

img = cv2.imread(picPath);
img_encode = cv2.imencode(".jpg" , img)[1];
data_encode = np.array(img_encode);
data_encode_c = data_encode.ctypes.data_as(ctypes.c_void_p);
data_len = len(data_encode);

loadLibrary = ctypes.cdll.LoadLibrary;
cLib = loadLibrary("./libc_send_pic.so");
cLib.shm_send_pic(data_encode_c , data_len);

 

1.the first sizeof(int) bytes of the data should be the length of the follow data,and the rest of them are the data of the picture

2.you can write a ctest.c to get the share memory and write the data into a file , then change the file externsion to "jpg" to verify the method