LabVIEW
dll import gets 1097 Error or crash
Hi,
I'm looking for help on integrating in Labview 2022 Q3 64-bit a dll generated in C from Matlab Coder to elaborate a 2D_in array (image) and generate a 2D_out array.
The arr_in is an image of n x n points, where n is not predefined and can vary (typically between 200 and 1000).
I tried importing the dll both using the import wizard or doing it manually in a Call Library Function node.
I could find no way to set 2D arrays as for arr_in and arr_out parameters
The only possibility I could find is to set the arr_in and arr_out parameters in the Call Library Function node as numeric, pass by array, and fix a specific length (in my case I guess it should be the maximum expected length, i-.e 1E6 for a n=1000). In this case I have to pass 1D arrays, but I always get this 1097 error code or, worse, a crash(see below).
As an example, I compiled a testfunc_arr.dll (attached below) from the following matlab code
In Matlab this code generates arr_out adding +1 to all the elements of arr_in. It works whatever the dimensions or size of arr_in.
I attach here both the dll and the vi resulting from the import wizard procedure.
Can somebody help?
Thank you
Fabio
The LabVIEW Call Library Node is strictly standard C compatible. What you show is however Matlab code. The Matlab compiler does a rather elaborate translation from its trivial looking syntax to something which is compatible with C programming.
Basically the Matlab code you show is absolutely useless in determining how the whole thing will need to be interfaced when Matlab has compiled it to a C DLL. Instead you will need the actually generated C header file and painstakingly make the Call Library Node follow that. And yes that may not be always possible. LabVIEW doesn't (easily) deal with C pointers, even less easily with C structures containing such pointers.
Typically your arr_in and arr_out will be a double pointer to an mxArray datatype in C, which is a fairly involved C data structure that is NOT just a pointer. It's pretty much not possible to interface that directly with the LabVIEW Call Library Node, unless you feel very adventurous about playing low level C compiler yourself.
Instead you should work through this tutorial very painstakingly and understand all the specialties of this, including the creation of the intermediate DLL to translate between the Matlab mxArray and normal LabVIEW datatypes. And yes it involves C programming, but trying to avoid the intermediate DLL would only mean that you need to know even more about how a C compiler aligns data in the memory and how to do involved pointer arithmetic.
@pokelto3 wrote:
Probably the update. I'm having the exact same issue right now. Can't open anything. Ctrl alt del goes to a black screen. Already booted and rebooted so many times
Well, this is expected result (but such "freezing" is unusual, the Windows is more or less resistant for the exceptions).
Anyway, it is slightly a little bit more complicated than you expect.
Because of this — MATLAB: Use C Arrays in the Generated Function Interfaces.
Probably you noticed, that in the exported DLL is not only one single function, but a little bit more payload.
Something like that should work (created quick and dirty, I haven't checked thoroughly for memory leaks, etc):
In general you don't need arr_out as input, but I will leave it "as is" in your original VI.
Attached VI in LV2018.
You can do it for 2D as well (and your DLL from MATLAB is already "prepared" for that). Just modify it something like that:
If you will accurately strip down into SubVIs, then it will looks more accurately.
And it works:
On the other hand, if you need to rotate image by one degree and save it to video ("for free"), then I would like to recommend to take a look into OpenCV, it is really much easier than in MATLAB.
@FabioR wrote:By rotating the 2nd image of an angle between 0 and 360°, step 1°, you get 360 images as output that must become frames of a movie file.
If I'll do it with OpenCV, then it will be like this:
This is the code for rotation:
IMAGEROTATOR_API void fnImageRotator(ImageArrHdl src, ImageArrHdl dst, double angle, LVError* Error)
{
Mat M, Dst;
int width = (*(src))->dimSizes[0];
int height = (*(src))->dimSizes[1];
Size size(height, width); //rows, cols
if (!((*(src))->pixel)) { SetError(Error, true, OCV_NULL_POINTER, "Null pointer"); return; };
Mat Src(size, CV_8U, (*(src))->pixel, width);
//https://docs.opencv.org/4.x/da/d6e/tutorial_py_geometric_transformations.html
M = getRotationMatrix2D(Point((width - 1) / 2, (height - 1) / 2), angle, 1.0);
warpAffine(Src, Dst, M, Size(width, height));
MgErr err = NumericArrayResize(uL, 2, (UHandle*)&(dst), width * height);
(*(dst))->dimSizes[0] = width;
(*(dst))->dimSizes[1] = height;
uint8_t* pixel_out = (*(dst))->pixel;
uint8_t* pixel_in = Dst.data;
if (!pixel_in || !pixel_out) { SetError(Error, true, OCV_NULL_POINTER, "Null pointer"); return; };
// Copy,line by line, the image into the LabVIEW Arrray
for (int y = 0; y < height; ++y) {
memcpy_s(pixel_out, width, pixel_in, width);
pixel_out += width; pixel_in += width;
}
}
And this is how to write frames to the Video:
IMAGEROTATOR_API void CreateVideo(char* file, ImageArrHdl src, LVError* Error)
{
Size size = Size((*(src))->dimSizes[1], (*(src))->dimSizes[0]);
vid = new VideoWriter(file, VideoWriter::fourcc('m', 'p', '4', 'v'), 25, size, false); //False - Grays
if (!vid) SetError(Error, true, 5000, "Unable to open Video File");
}
IMAGEROTATOR_API void AddFrame(ImageArrHdl src, LVError* Error)
{
Size size((*(src))->dimSizes[1], (*(src))->dimSizes[0]); //rows, cols
Mat frame(size, CV_8U, (*(src))->pixel, (*(src))->dimSizes[0]);
vid->write(frame);
}
IMAGEROTATOR_API void VideoClose(LVError* Error)
{
vid->release();
}
And LabVIEW code:
I will leave code on GitHub, may be will be useful someday for someone.
Errors handling is minimal and I'm too lazy to pass vidfeowriter as parameter, therefore global var, but it is just an example.
Dear Andrey,
I see that here you don't use memory management like MoveBlock, but just send the 2D arry as an "Adapt to type" parameter . Is this due to the fact that you are not using matlab to build the dll? I'm no programmer, so please excuse silly questions.
Concerning your code on Github, it's not running because the dll is seemingly missing:
Finally, you suggested to use OpenCV. As far as I understood, one can use it in Python or in C/C++. Would it be the same if I want to build a dll to be imported in Labview? I'd prefer Python since it is seemingly simpler to learn than C/C++
Thank you
Fabio
