Tracking Rectangles with Java/C++

[abrightwell]

Have you read through this whitepaper?

http://firstforge.wpi.edu/sf/docman/...n.root/doc1302

While it doesn't talk specifically to functions or specific library calls, it does talk about different techniques specifically related to this years game.

[Greg McKaskle]

Just so there is no misunderstanding, the vision libraries that LabVIEW uses are equally accessible from C/C++. The NI product for C development is called LabWindows CVI, so the vision documentation with the CVI suffix is all about the C/C++ entry points.

C:\Program Files\National Instruments\Vision\Documentation contains general documentation about vision processing and LV and C/C++ specific documents and others specific to Vision Assistant. It also has a calibration grid file if you need to correct the images for lens distortion.

The libraries are installed on the cRIO and if you have installed Vision Assistant, I believe you have them on the laptop as well.

It has been a while since I've looked at the WPI wrappers, and at least initially, they tended to hide the imaq entry point rather than simplify them. Perhaps the Examples for C based image processing will be helpful. They are located at C:\Program Files\National Instruments\Vision\Examples\MSVC.

NI doesn't have Java wrappers for the C libraries or for much else. I know some have been added to WPILib, but it is far from complete. If you are more familiar with OpenCV, that is certainly a good option. I wouldn't expect it to be that much difference in performance or capabilities, but both libraries have their specializations and benefits. If you search online, you can probably find some comparisons.

Once again, I'd also encourage you to take advantage of vision assistant, its code generation features and the vision concept manual.

Greg McKaskle

[basicxman]

Originally Posted by Greg McKaskle

Just so there is no misunderstanding, the vision libraries that LabVIEW uses are equally accessible from C/C++. The NI product for C development is called LabWindows CVI, so the vision documentation with the CVI suffix is all about the C/C++ entry points.

So I've spent the morning looking around nivision.h, the "NI Vision for LabWindows/CVI Function Reference Help", and the old ellipsis tracking code to figure out tracking rectangles in C++. Here's a snippet of [entirely untested as I don't currently have access to a cRio] code.

void Camera::FindRectangles() {
    HSLImage  *rawImage  = camera.GetImage();
    MonoImage *monoImage = rawImage->GetLuminancePlane();
    Image     *image     = monoImage->GetImaqImage();
    workingImageWidth  = monoImage->GetWidth();
    workingImageHeight = monoImage->GetHeight();
    delete monoImage;
    delete rawImage;

    RectangleDescriptor *rectangleDescriptor = new RectangleDescriptor;
    rectangleDescriptor->minWidth  = 0;
    rectangleDescriptor->minHeight = 0;
    rectangleDescriptor->maxWidth  = workingImageWidth;
    rectangleDescriptor->maxHeight = workingImageHeight;

    int numCurrentMatches;
    RectangleMatch *temp;
    temp = imaqDetectRectangles(image,
                                rectangleDescriptor,
                                NULL, // Default curve options as per manual.
                                NULL, // Default shape detection options.
                                NULL, // (ROI) Whole image should be searched.
                                &numCurrentMatches);
    matches->erase(matches->begin(), matches->end());
    matches = new vector<RectangleMatch>;
    for (int i = 0; i < numCurrentMatches; i++)
        matches->push_back(temp[i]);
    
    imaqDispose(temp);
}

EDIT: CVI manual located at C:\Program Files (x86)\National Instruments\Vision\Documentation\VDM_CVI_User_Manu al.pdf

[scottbot95]

Would I be correct in assuming that in your example code, Camera is a class you made?

[basicxman]

Originally Posted by scottbot95

Would I be correct in assuming that in your example code, Camera is a class you made?

Yes, once we have our tracking code working completely and performing as we'd like, I'll likely post the full source code and an accompanying whitepaper.

[basicxman]

Originally Posted by basicxman

Here's a snippet of [entirely untested as I don't currently have access to a cRio] code.

Do not use this snippet! After I finally got to experiment with the camera for a while today, I've fixed some flaws in that script and found a better way of doing it entirely.