public static Contour TraceContour(int a_iStartingPixelIndex, NeighborDirection a_eStartingDirection, int a_iContourLabel, BinarizedImage a_rBinarizedImage, int[] a_rLabelMap)
{
int iPixelIndexTrace;
NeighborDirection eDirectionNext = a_eStartingDirection;
FindNextPoint(a_iStartingPixelIndex, a_eStartingDirection, a_rBinarizedImage, a_rLabelMap, out iPixelIndexTrace, out eDirectionNext);
Contour oContour = new Contour(a_iContourLabel);
oContour.AddFirst(a_rBinarizedImage.PixelIndex2Coords(iPixelIndexTrace));
int iPreviousPixelIndex = a_iStartingPixelIndex;
int iCurrentPixelIndex = iPixelIndexTrace;
bool bDone = (a_iStartingPixelIndex == iPixelIndexTrace);
// Choose a bias factor
// The bias factor points to exterior if tracing an outer contour
// The bias factor points to interior if tracing an inner contour
float fOrthoBiasFactor;
if (a_eStartingDirection == NeighborDirection.DirectionUpRight) // inner contour
{
fOrthoBiasFactor = -0.2f;
}
else // outer contour
{
fOrthoBiasFactor = 0.2f;
}
while (bDone == false)
{
a_rLabelMap[iCurrentPixelIndex] = a_iContourLabel;
NeighborDirection eDirectionSearch = (NeighborDirection)(((int)eDirectionNext + 6) % 8);
int iNextPixelIndex;
FindNextPoint(iCurrentPixelIndex, eDirectionSearch, a_rBinarizedImage, a_rLabelMap, out iNextPixelIndex, out eDirectionNext);
iPreviousPixelIndex = iCurrentPixelIndex;
iCurrentPixelIndex = iNextPixelIndex;
bDone = (iPreviousPixelIndex == a_iStartingPixelIndex && iCurrentPixelIndex == iPixelIndexTrace);
if (bDone == false)
{
// Apply some bias to inner and outer contours to avoid them overlap
// Use the orthogonal vector to direction
NeighborDirection eOrthoBiasDirection = (NeighborDirection)(((int)eDirectionNext + 6) % 8); // == direction - 2 % 8 but easier to compute (always positive)
Vector2 f2Bias = fOrthoBiasFactor * BinarizedImage.GetDirectionVector(eOrthoBiasDirection);
// Add bias to pixel pos
Vector2 f2BiasedPos = f2Bias + a_rBinarizedImage.PixelIndex2Coords(iNextPixelIndex);
// Add biased pos to contour
oContour.AddFirst(f2BiasedPos);
}
}
return(oContour);
}