/// <summary>
/// Creates a mask from an image. All light sources are detected via a hysteresis algorithm and flagged in the mask.
/// </summary>
/// <param name="Input">Input image data.</param>
/// <param name="Position">Data position in the image.</param>
/// <param name="Properties">Bag of mask data.</param>
static void GenerateMask(double[,] Input, ImageSegmentPosition Position, MaskProperties Properties)
{
int Width = Input.GetLength(1);
int Height = Input.GetLength(0);
int i, j;
PixelPoint pxp = new PixelPoint();
/* Compute masking thresholds */
double UpperThreshold = Properties.UTM * Properties.StDev + Properties.Mean;
double LowerThreshold = Properties.LTM * Properties.StDev + Properties.Mean;
for (i = 0; i < Height; i++)
{
for (j = 0; j < Width; j++)
{
pxp.X = j + Position.Alignment.X;
pxp.Y = i + Position.Alignment.Y;
if (pxp.Y >= Properties.MaskData.Length)
{
break;
}
if (pxp.X >= Properties.MaskData[(int)pxp.Y].Length)
{
break;
}
if (Properties.MaskData[(int)pxp.Y][(int)pxp.X])
{
continue;
}
if (Input[i, j] > UpperThreshold)
{
BitmapFill(Properties.MaskData, Input, Position.Alignment, pxp, LowerThreshold, Properties.MaskRadiusMultiplier, Properties.ExtraMaskRadius, out Filtering.Star? Star);
if (Star != null)
{
Filtering.Star S = Star.Value; S.EqCenter = Position.WCS.GetEquatorialPoint(S.PixCenter); lock (Properties.StarList) Properties.StarList.FixedStarList.Add(S);
}
}
}
}
}
/// <summary>
/// Runs the hysteresis connected component detection algorithm for light sources. At the end also applies the extra circular masking.
/// </summary>
/// <param name="Mask">Mask array.</param>
/// <param name="MaskData">Masking image data.</param>
/// <param name="Alignment">Position of data in the image.</param>
/// <param name="DPoint">Starting point for the connected component algorithm.</param>
/// <param name="LowerThreshold">Lower hysteresis threshold.</param>
/// <param name="RadiusMultiplier">Ratio between extra masking circle radius and light source radius.</param>
/// <param name="ExtraRadius">Extra radius for the masking circle.</param>
/// <param name="Star">The potential output star.</param>
static void BitmapFill(BitArray[] Mask, double[,] MaskData, PixelPoint Alignment, PixelPoint DPoint, double LowerThreshold, double RadiusMultiplier, double ExtraRadius, out Filtering.Star?Star)
{
Queue <PixelPoint> PointQ = new Queue <PixelPoint>();
PointQ.Enqueue(DPoint);
double XMean = 0, YMean = 0, XSquare = 0, YSquare = 0, XY = 0;
int PCount = 0;
double Flux = 0;
while (PointQ.Count > 0)
{
PixelPoint pt = PointQ.Dequeue();
if (pt.X < 0 || pt.X >= Mask[0].Length)
{
continue;
}
if (pt.Y < 0 || pt.Y >= Mask.Length)
{
continue;
}
if (Mask[(int)pt.Y][(int)pt.X])
{
continue;
}
double dX = pt.X - Alignment.X;
double dY = pt.Y - Alignment.Y;
dX = Math.Round(dX); dY = Math.Round(dY);
if (dX < 0 || dX >= MaskData.GetLength(1))
{
continue;
}
if (dY < 0 || dY >= MaskData.GetLength(0))
{
continue;
}
if (MaskData[(int)dY, (int)dX] > LowerThreshold)
{
Mask[(int)pt.Y][(int)pt.X] = true;
PointQ.Enqueue(new PixelPoint()
{
X = pt.X - 1, Y = pt.Y
});
PointQ.Enqueue(new PixelPoint()
{
X = pt.X + 1, Y = pt.Y
});
PointQ.Enqueue(new PixelPoint()
{
X = pt.X, Y = pt.Y - 1
});
PointQ.Enqueue(new PixelPoint()
{
X = pt.X, Y = pt.Y + 1
});
XMean += pt.X; YMean += pt.Y;
XSquare += pt.X * pt.X; YSquare += pt.Y * pt.Y;
XY += pt.X * pt.Y;
PCount++;
Flux += MaskData[(int)dY, (int)dX];
}
}
/* Computes size of and shape of the light source */
XMean /= PCount;
YMean /= PCount;
XSquare /= PCount;
YSquare /= PCount;
XY /= PCount;
XSquare -= XMean * XMean;
YSquare -= YMean * YMean;
XY -= XMean * YMean;
double Radius = Math.Sqrt(XSquare + YSquare);
SourceEllipse Shape = new SourceEllipse(XSquare, XY, YSquare);
/* If not to irregular, suppose it is a star and apply extra masking. */
if (Shape.SemiaxisMajor < 3 * Shape.SemiaxisMinor)
{
FillMarginsExtra(Mask, new PixelPoint()
{
X = XMean, Y = YMean
}, Radius * RadiusMultiplier + ExtraRadius);
Star = new Filtering.Star()
{
Shape = Shape, PixCenter = new PixelPoint()
{
X = XMean, Y = YMean
}, PixRadius = Radius, Flux = Flux
};
}
else
{
Star = null;
}
}
