void FilterLed::FindStar	(	std::vector< Led > &	leds,
		int	xc,
		int	yc,
		bool	circle = false
	)		const

Definition at line 396 of file FilterLed.cc.

References mag.

Referenced by MStarguider::ProcessFrame(), and SetCut().

{
    // fBox: radius of the inner (signal) box
    // Radius of the outer box is fBox*sqrt(2)

    //
    // Define inner box in which to search the signal
    //
    const int x0 = max(xc-fBoxX, 0);
    const int y0 = max(yc-fBoxY, 0);
    const int x1 = min(xc+fBoxX, fW);
    const int y1 = min(yc+fBoxY, fH);

    //
    // Define outer box (excluding inner box) having almost
    // the same number of pixels in which the background
    // is calculated
    //
    const double sqrt2 = sqrt(2.);

    const int xa = max(xc-(int)nearbyint(fBoxX*sqrt2), 0);
    const int ya = max(yc-(int)nearbyint(fBoxY*sqrt2), 0);
    const int xb = min(xc+(int)nearbyint(fBoxX*sqrt2), fW);
    const int yb = min(yc+(int)nearbyint(fBoxY*sqrt2), fH);

    //
    // Calculate average and sdev for a square
    // excluding the inner part were we expect
    // the signal to be.
    //
    double sum = 0;
    double sq  = 0;

    int n=0;
    for (int x=xa; x<xb; x++)
        for (int y=ya; y<yb; y++)
        {
            if (x>=x0 && x<x1 && y>=y0 && y<y1)
                continue;

            uint8_t &b = fImg[y*fW+x];

            sum += b;
            sq  += b*b;
            n++;
        }

    sum /= n;
    sq  /= n;

    // 254 because b<=max and not b<max
    const double sdev = sqrt(sq-sum*sum);
    const uint8_t   max  = sum+fCut*sdev>254 ? 254 : (uint8_t)(sum+fCut*sdev);

    //
    // clean image from noise
    // (FIXME: A lookup table could accelerate things...
    //
    n=0;
    for (int x=x0; x<x1; x++)
        for (int y=y0; y<y1; y++)
        {
            uint8_t &b = fImg[y*fW+x];
            if (b<=max)
                b = 0;
            else
                n++;
        }

    //
    // Mark the background region
    //
    for (int x=xa; x<xb; x+=2)
    {
        fImg[ya*fW+x]=0xf0;
        fImg[yb*fW+x]=0xf0;
    }
    for (int y=ya; y<yb; y+=2)
    {
        fImg[y*fW+xa]=0xf0;
        fImg[y*fW+xb]=0xf0;
    }

    //
    // Check if any pixel found...
    //
    if (n<5)
        return;

    //
    // Get the mean position of the star
    //
    float mx, my;
    unsigned int mag;
    int pos = box ? GetMeanPositionBox(xc, yc, fBoxX-1, fBoxY-1, mx, my, mag)
        : GetMeanPosition(xc, yc, fBoxX-1, fBoxY-1, mx, my, mag);

    if (pos<0 || pos>=fW*fH || fImg[pos]<sum+fCut*sdev)
        return;

    //    cout << "Mean=" << sum << "  SDev=" << sdev << "  :  ";
    //    cout << "Sum/n = " << sum << "/" << n << " = " << (n==0?0:mag/n) << endl;

    leds.push_back(Led(mx, my, 0, -2.5*log10((float)mag)+13.7));
}

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