public static void PencilSketch(
InputArray src, OutputArray dst1, OutputArray dst2,
float sigmaS = 60, float sigmaR = 0.07f, float shadeFactor = 0.02f)
{
if (src == null)
throw new ArgumentNullException(nameof(src));
if (dst1 == null)
throw new ArgumentNullException(nameof(dst1));
if (dst2 == null)
throw new ArgumentNullException(nameof(dst2));
src.ThrowIfDisposed();
dst1.ThrowIfNotReady();
dst2.ThrowIfNotReady();
NativeMethods.photo_pencilSketch(
src.CvPtr, dst1.CvPtr, dst2.CvPtr, sigmaS, sigmaR, shadeFactor);
GC.KeepAlive(src);
dst1.Fix();
dst2.Fix();
}