Python 把OpenCV 获取的图像传递到C
Python 把OpenCV 获取的图像传递到C
用OpenCV Python来开发,如果想要用到一些C/C++的图像处理库,就需要创建Python的C/C++扩展,然后把数据从Python传递到底层处理。这里分享下如何在C/C++层获取数据。
参考原文:How to Convert OpenCV Image Data from Python to C
作者:Xiao Ling
翻译:yushulx
开发环境
- Dynamsoft Barcode Reader 4.2
- Python version: 2.7.0
- OpenCV version: 2.4.10. Download cv2.pyd
- Windows 10
- USB webcam
Python C/C++扩展
把DynamsoftBarcodeReaderx86.dll和cv2.pyd拷贝到目录Python27\Lib\site-packages。
OpenCV Python获取的图像数据类型是numpy.ndarray:
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> rval, frame = vc.read();
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> print type(frame)
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> <type 'numpy.ndarray'>
在C层我们希望能获取到数据的指针。查看OpenCV源码文件opencv\modules\python\src2\cv2.cv.hpp可以找到方法:
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PyObject *o;
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if (!PyArg_ParseTuple(args, "O", &o))
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return NULL;
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PyObject *ao = PyObject_GetAttrString(o, "__array_struct__");
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PyObject *retval;
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if ((ao == NULL) || !PyCObject_Check(ao)) {
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PyErr_SetString(PyExc_TypeError, "object does not have array interface");
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return NULL;
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}
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PyArrayInterface *pai = (PyArrayInterface*)PyCObject_AsVoidPtr(ao);
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if (pai->two != 2) {
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PyErr_SetString(PyExc_TypeError, "object does not have array interface");
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Py_DECREF(ao);
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return NULL;
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}
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// Construct data with header info and image data
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char *buffer = (char*)pai->data; // The address of image data
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int width = pai->shape[1]; // image width
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int height = pai->shape[0]; // image height
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int size = pai->strides[0] * pai->shape[0]; // image size = stride * height
这样就可以了。现在可以用这个数据做点事情,比如调用barcode接口来做检测。我依然用Dynamsoft Barcode Reader SDK做示例。首先需要构建一下数据:
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char *total = (char *)malloc(size + 40); // buffer size = image size + header size
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memset(total, 0, size + 40);
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BITMAPINFOHEADER bitmap_info = {40, width, height, 0, 24, 0, size, 0, 0, 0, 0};
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memcpy(total, &bitmap_info, 40);
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// Copy image data to buffer from bottom to top
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char *data = total + 40;
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int stride = pai->strides[0];
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for (int i = 1; i <= height; i++) {
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memcpy(data, buffer + stride * (height - i), stride);
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data += stride;
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}
接下来就可以检测barcode了:
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// Dynamsoft Barcode Reader initialization
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__int64 llFormat = (OneD | QR_CODE | PDF417 | DATAMATRIX);
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int iMaxCount = 0x7FFFFFFF;
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ReaderOptions ro = {0};
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pBarcodeResultArray pResults = NULL;
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ro.llBarcodeFormat = llFormat;
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ro.iMaxBarcodesNumPerPage = iMaxCount;
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printf("width: %d, height: %d, size:%d\n", width, height, size);
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int iRet = DBR_DecodeBuffer((unsigned char *)total, size + 40, &ro, &pResults);
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printf("DBR_DecodeBuffer ret: %d\n", iRet);
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free(total); // Do not forget to release the constructed buffer
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// Get results
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int count = pResults->iBarcodeCount;
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pBarcodeResult* ppBarcodes = pResults->ppBarcodes;
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pBarcodeResult tmp = NULL;
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retval = PyList_New(count); // The returned Python object
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PyObject* result = NULL;
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for (int i = 0; i < count; i++)
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{
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tmp = ppBarcodes[i];
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result = PyString_FromString(tmp->pBarcodeData);
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printf("result: %s\n", tmp->pBarcodeData);
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PyList_SetItem(retval, i, Py_BuildValue("iN", (int)tmp->llFormat, result)); // Add results to list
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}
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// release memory
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DBR_FreeBarcodeResults(&pResults);
在Windows上构建Python扩展需要先设置一下,不然会出错。我使用Visual Studio 2015。命令行如下:
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SET VS90COMNTOOLS=%VS140COMNTOOLS%
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python setup.py build install
好了。现在可以用Python脚本来调用了。首先打开摄像头:
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import cv2
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from dbr import *
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import time
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vc = cv2.VideoCapture(0)
接下来读取一帧的数据:
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cv2.imshow(windowName, frame)
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rval, frame = vc.read();
现在可以实时检测barcode了:
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initLicense("<license>") # Invalid license is fine.
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results = decodeBuffer(frame)
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if (len(results) > 0):
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print "Total count: " + str(len(results))
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for result in results:
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print "Type: " + types[result[0]]
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print "Value: " + result[1] + "\n"
源码
https://github.com/yushulx/opencv-python-webcam-barcode-reader
文章来源: blog.csdn.net,作者:网奇,版权归原作者所有,如需转载,请联系作者。
原文链接:blog.csdn.net/jacke121/article/details/80281825
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