All values are shifted

beginners
#1

I have a method where i find blobs and calculate a angle.
In that method i output using:

  
printf("a: %.3f\t%.3f\t\t%.3f\n", tang.angle, tang.centroid.x, tang.boundingRect.x);

Which gives this:

  
a: -1.585	689.356		605.000  
a: 0.001	446.873		362.000  
a: 2.858	1118.321		1036.000  
a: -2.417	301.964		221.000  
a: 0.778	805.566		729.000  
a: -0.790	729.381		657.000  
a: -1.571	185.957		111.000  
a: -0.781	383.021		309.000  
a: 0.097	989.214		915.000  
a: 2.288	534.049		466.000

Then directly after that method i excecute:

  
        vector<ofxDTangible> &tan = tangibleFinder->getTangibles();  
        for(int i = 0; i < tan.size(); i++ ) {  
           ofxDTangible &t = tan[i];  
              
            printf("i: %.3f\t%.3f\t\t%.3f\n", t.angle, t.centroid.x, t.boundingRect.x);  
              
             t.draw();  
        }

which gives me:

  
  
i: 0.000	689.356		605.000  
i: -1.585	446.873		362.000  
i: 0.001	1118.321		1036.000  
i: 2.858	301.964		221.000  
i: -2.417	805.566		729.000  
i: 0.778	729.381		657.000  
i: -0.790	185.957		111.000  
i: -1.571	383.021		309.000  
i: -0.781	989.214		915.000  
i: 0.097	534.049		466.000

Note that all angles (the first column) are shifted one row lower!
Please help me on this, it’s driving me nuts.

Here is the method that sets the angle:
(once more, directly after this the code from above is executed).

  
int ofxDTangibleFinder::findTangibles(ofxCvGrayscaleImage& input) {  
      
    if(!checkForSetupCorrect()) {  
        return 0;  
    }  
      
    _tangibles.clear();  
      
    contourFinder.findContours(input, getMinRectArea(), getMaxRectArea(), getMaxTangibles(), false);  
      
    // from the blobs we found  
    // we need to check if the aspect ratio is about to be correct  
  
    for(int i = 0; i < contourFinder.nBlobs; i++) {  
        ofxCvBlob &blob = contourFinder.blobs.at(i);  
          
        float aspectRatio = min(blob.boundingRect.getWidth(), blob.boundingRect.getHeight()) / max(blob.boundingRect.getWidth(), blob.boundingRect.getHeight());  
          
        //printf("aspectRatio: %f\n", aspectRatio);  
          
        if (1 - aspectRatio < getMaxAspectDeviation()) {  
              
            ofxDTangible tang = ofxDTangible(blob);  
            _tangibles.push_back(tang);  
              
            // find the angle  
            if (_detectKnobs) {  
                ofRectangle &r = tang.boundingRect;  
                bool knobResult = knobAngleDetector->detect(input, r.getX(), r.getY(), r.getWidth(), r.getHeight());  
                if(knobResult) {  
                    tang._isKnob = true;  
                    //printf("angle: %f\n", knobAngleDetector->angle());  
                    tang.angle = knobAngleDetector->angle();  
                      
                    printf("a: %.3f\t%.3f\t\t%.3f\n", tang.angle, tang.centroid.x, tang.boundingRect.x);  
                      
                    tang.draw();  
                      
                }  
            }  
              
        }  
    }  
    printf("\n");  
      
    //printf("%lu\n", _tangibles.size());  
    return _tangibles.size();  
}
#2

when you insert an object in a vector you are making a copy of it so in your last code you need to push_back after the if(detectKnobs) code or it won’t have any effect

#3

Thanks. That’s different from java so it’s quite a easy mistake for me :slight_smile:
I already fixed it by making a new method to figure out the knob. But it’s good that i also know now what was causing the problem.