/// <summary>
/// Returns the coordinates of the pixels that lie on the sampling line, which is defined by the
/// <paramref name="startingPosition"/> and its <paramref name="angle"/> to the edge of the
/// <paramref name="image"/>. The <paramref name="startingPosition"/> will not be returned in the
/// result set.
/// </summary>
/// <remarks>
/// <example>
/// Here's an example using the angle of 45 degrees.
/// <![CDATA[
/// ^
/// | E E = edge of the image
/// | \ \ = sampling line
/// | \ c = center
/// | \
/// | \
/// | \
/// | c
/// |
/// .
/// .
/// . --------------------------->
/// ]]>
/// </example>
/// </remarks>
internal static SamplingLine GetSamplingLineForAngle(
BinaryImage image,
MatrixPosition startingPosition,
int angle)
{
const int MaxIterationLimit = 50000;
var samplingLine = new SamplingLine();
MatrixPosition nextPosition;
double phi = (angle + 180d) * Math.PI / 180d;
int r = 1;
do
{
var deltaN = (int)Math.Round(r * Math.Cos(phi), 0, MidpointRounding.ToZero);
var deltaM = (int)Math.Round(r * Math.Sin(phi), 0, MidpointRounding.ToZero);
nextPosition = new MatrixPosition(startingPosition.M + deltaM, startingPosition.N + deltaN);
if (nextPosition != startingPosition
// ReSharper disable once SimplifyLinqExpressionUseAll
&& !samplingLine.ContainsPosition(nextPosition) &&
IsPositionWithinImage(image, nextPosition))
{
var pointOfInterest = new SamplingPoint(nextPosition, r);
samplingLine.Add(pointOfInterest);
}
r++;
} while (IsPositionWithinImage(image, nextPosition) && r < MaxIterationLimit);
return(samplingLine);
}
private static IEnumerable <int> FindAllBlackPixelsOnSamplingLine(
BinaryImage image,
SamplingLine samplingLine)
{
return(from samplingPoints in samplingLine.SamplingPoints
where image[samplingPoints.Position] == BinaryImage.Black
select samplingPoints.Radius);
}
internal static IReadOnlyCollection <SamplingLine> GetSamplingLines(BinaryImage image, int numberOfSamplingLines)
{
CheckNumberOfSamplingLinesIsInRange(numberOfSamplingLines);
double angleIncrement = 360d / numberOfSamplingLines;
var samplingLines = new SamplingLine[numberOfSamplingLines];
var center = GetCenterOfObjectIn(image);
for (int samplingIndex = 0; samplingIndex < numberOfSamplingLines; samplingIndex++)
{
// value of the angle, at which the sampling from the center will be taken.
int angle = (int)Math.Round(samplingIndex * angleIncrement, 0, MidpointRounding.ToZero);
var samplingLine = GetSamplingLineForAngle(image, center, angle);
samplingLines[samplingIndex] = samplingLine;
}
return(samplingLines);
}
