relabel blobs after cvFilterByArea (feature request) about cvblob HOT 2 OPEN

I've implemented cvRelabel and it works well for me:

void cvRelabel(CvBlobs blobs, IplImage* imgLabel) {
    int i=1;
    int stepLbl = imgLabel->widthStep/(imgLabel->depth/8);
    for (CvBlobs::const_iterator it=blobs.begin(); it!=blobs.end(); ++it, i++) {
        CvBlob* blob = it->second;
        if(blob->label != i) {            
            for(int y=0; y<imgLabel->height; y++ ) {
                CvLabel *label = (CvLabel *) imgLabel->imageData + y * stepLbl;
                for(int x=0; x<imgLabel->width; x++) {
                    if(*label == blob->label) {
                        *label = i;  
                    }
                    label++;
                }
            }
            blob->label = i;
        }
    }
}

Hi Pablo,

CvBlobs is not a `vector` but a `map`. This way the "indexes" don't change when 
you filter blobs. I used maps for that reason. For example, you have:

  blobs[0], blobs[1], blobs[2], blobs[3]

After filter you could have:

  blobs[1], blobs[3]

Of course, if you use iterators you'll see that the "first" blobs has 
`label=1`, and next blob has `label=3`, but their indexes are the same. If you 
need to know the "index" of a iterator you can use `it->first`, but it should 
be the equal to `it->second->label`.

So, do a relabel or something like that seems unnecessary to me :-S Can you 
overcome the problem in any other way?

I could refactor all the library and use only vector instead of maps (vector 
must be more efficient), but I find maps easier when you program.

Regards,

Cristóbal