python 调用C的DLL案例

前言： python不能直接调用C++只能调用纯C的DLL

此处案例是python模仿opencv的cv2包，但是用c的DLL调用

import os
import csv
import time
import ctypes
from ctypes import *
opencv = CDLL("opencv_world310.dll")

class IplTileInfo(Structure):
        _fields_ = []

    class IplROI(Structure):
        _fields_ =[
            ('coi', c_int),
            ('xOffset', c_int),
            ('yOffset', c_int),
            ('width', c_int),
            ('height', c_int)
        ]
    class IplImage(Structure):
        def __repr__(self):
            res = []
            for field in self._fields_:
                if field[0] in ['imageData', 'imageDataOrigin']:
                    continue
                res.append('%s=%s' % (field[0], repr(getattr(self, field[0]))))
            return self.__class__.__name__ + '(' + ','.join(res) + ')'

    IplImage._fields_ = [
    ("nSize",c_int),
    ("ID",c_int),
    ("nChannels",c_int),
    ("alphaChannel",c_int),
    ("depth",c_int),
    ("dataOrder",c_int),
    ("origin",c_int),
    ("align",c_int),
    ("width",c_int),
    ("height",c_int),
    ("imageSize",c_int),
    ("widthStep",c_int),
    ("BorderMode",c_int*4),
    ("BorderConst",c_int*4),
    ("colorModel",c_char*4),
    ("channelSeq",c_char*4),
    ("imageData",c_void_p),
    ("imageDataOrigin",c_char_p),
    ("imageId",c_void_p),
    ("roi", POINTER(IplROI)),
    ("maskROI", POINTER(IplImage)),
    ("tileInfo", POINTER(IplTileInfo))]

    loadimageFunc=opencv.cvLoadImage
    loadimageFunc.argtypes  =[c_char_p,c_int]
    loadimageFunc.restype = POINTER(IplImage)
    cvimage = loadimageFunc(mpath,2).contents

    pt=POINTER(c_char)
    data=ctypes.cast(cvimage.imageData,pt)   # 这里的转换非常重要

等同于

import os
import csv
import time
import cv2   #python opencv
import ctypes
from cv2 import *
from ctypes import *   

cvimage = cv2.imread(mpath, cv2.IMREAD_ANYDEPTH)
data=cvimage.ctypes.data_as(ctypes.POINTER(ctypes.c_char))