public void ComputeGradient(Arr source, GradientOperator gradientOperator, double gradientThreshold)
{
// gaussian filtering
CV.Smooth(source, _smoothed, SmoothMethod.Gaussian, 5, 5, 1.0);
// calculate gradients
switch (gradientOperator)
{
case GradientOperator.Prewitt:
CV.Filter2D(_smoothed, _gradientX, PrewittX);
CV.Filter2D(_smoothed, _gradientY, PrewittY);
if (gradientThreshold < 0.0)
{
gradientThreshold = 6.0;
}
break;
case GradientOperator.Sobel:
CV.Sobel(_smoothed, _gradientX, 1, 0);
CV.Sobel(_smoothed, _gradientY, 0, 1);
break;
case GradientOperator.Scharr:
CV.Sobel(_smoothed, _gradientX, 1, 0, -1);
CV.Sobel(_smoothed, _gradientY, 0, 1, -1);
break;
default:
throw new Exception($"Unknown gradient operator: {gradientOperator}");
}
// calculate absolute values for gradients
CV.ConvertScaleAbs(_gradientX, _absGradientX);
CV.ConvertScaleAbs(_gradientY, _absGradientY);
// merge gradients
// d = 0.5 * abs(dx) + 0.5 * abs(dy)
CV.AddWeighted(_absGradientX, 0.5, _absGradientY, 0.5, 0.0, GradientMap);
// eliminate gradient weak pixels
CV.Threshold(GradientMap, GradientMap, gradientThreshold, 255, ThresholdTypes.ToZero);
// edge direction
// abs(dx) >= abs(dy) => VERTICAL
CV.Cmp(_absGradientX, _absGradientY, DirectionMap, ComparisonOperation.GreaterOrEqual);
}