/// <inheritdoc />
public Bitmap Filter(Bitmap bitmap, BitMatrix kernel)
{
if (bitmap is null)
{
throw new ArgumentNullException(nameof(bitmap));
}
if (kernel is null)
{
throw new ArgumentNullException(nameof(kernel));
}
if (bitmap.PixelFormat != PixelFormat.Format32bppArgb)
{
throw new NotSupportedException(Errors.NotSupported);
}
var destination = new Bitmap(bitmap);
var source = bitmap.AdjustBorder(kernel.ColumnCount / 2, Color.Black);
var sourceBitmapData = source.LockBits(
new Rectangle(0, 0, source.Width, source.Height),
ImageLockMode.ReadOnly, source.PixelFormat);
var destinationBitmapData = destination.LockBits(
new Rectangle(0, 0, source.Width, source.Height),
ImageLockMode.WriteOnly, destination.PixelFormat);
var size = source.Size;
var step = Image.GetPixelFormatSize(PixelFormat.Format32bppArgb) / 8;
unsafe
{
var sourceStartPtr = (byte *)sourceBitmapData.Scan0.ToPointer();
var destinationStartPtr = (byte *)destinationBitmapData.Scan0.ToPointer();
var kernelOffset = (byte)(kernel.ColumnCount / 2);
var options = new ParallelOptions()
{
MaxDegreeOfParallelism = Environment.ProcessorCount - 1
};
var mask = kernel.To2DArray();
Parallel.For(kernelOffset, size.Height - kernelOffset, options, y =>
{
//get the address of a new line, considering a kernel offset
var sourcePtr = sourceStartPtr + y * sourceBitmapData.Stride + kernelOffset * step;
var destinationPtr = destinationStartPtr + y * destinationBitmapData.Stride + kernelOffset * step;
//a pointer, which gets addresses of the elements in the radius of a structured element
byte *elementPtr;
for (int x = kernelOffset; x < size.Width - kernelOffset; ++x, sourcePtr += step, destinationPtr += step)
{
for (int kernelRow = -kernelOffset; kernelRow <= kernelOffset; ++kernelRow)
{
for (int kernelColumn = -kernelOffset; kernelColumn <= kernelOffset; ++kernelColumn)
{
//get the address of a current element
elementPtr = sourcePtr + kernelColumn * step + kernelRow * sourceBitmapData.Stride;
if (mask[kernelRow + kernelOffset, kernelColumn + kernelOffset] && elementPtr[0] == 255)
{
destinationPtr[0] = destinationPtr[1] = destinationPtr[2] = 255;
goto IsDilated;
}
}
}
IsDilated:;
}
});
}
source.UnlockBits(sourceBitmapData);
destination.UnlockBits(destinationBitmapData);
source.Dispose();
return(destination);
}
