Modify pixel data of an existing DICOM file by writing some text over it using ImageSharp

Program.cs

using DcmPixelData;
using FellowOakDicom;
using FellowOakDicom.Imaging;
using FellowOakDicom.Imaging.NativeCodec;
using FellowOakDicom.IO.Buffer;
using SixLabors.Fonts;
using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Processing;
using SixLabors.ImageSharp.Drawing.Processing;
using SixLabors.ImageSharp.PixelFormats;

// Configure SixLabors Fonts
var fontCollection = new FontCollection();
fontCollection.Add("Roboto-Regular.ttf");
var fontFamily = fontCollection.Get("Roboto");
var font = fontFamily.CreateFont(36, FontStyle.Bold);

// Configure Fellow Oak DICOM
new DicomSetupBuilder().RegisterServices(x =>
{
    x.AddFellowOakDicom();
    x.AddImageManager<ImageSharpImageManager>();
    x.AddTranscoderManager<NativeTranscoderManager>();
    
}).Build();

var directory = @"C:\Users\a.moerman\Downloads\DOPA-3608\St1b";
var files = Directory.EnumerateFiles(directory);

foreach (var adaptedFile in Directory.EnumerateFiles(directory, "*-lic.dcm"))
{
    Console.WriteLine("Deleting " + adaptedFile);
    File.Delete(adaptedFile);
}

foreach (var file in files)
{
    var dicomFile = DicomFile.Open(file);
    
    var frame = 0;
    var dicomImage = new DicomImage(dicomFile.Dataset) { OverlayColor = 0xFFFFFF };

    Console.WriteLine("Rendering " + file);
    using var imageSharpImage = (dicomImage.RenderImage(frame) as ImageSharpImage)!;
                
    // dicomFile.Save(dicomFile.File.Name.Replace(".dcm", "-adapted.dcm"));

    using Image image = imageSharpImage.RenderedImage.CloneAs<L16>()!;
    
    image.Mutate(x =>
    {
        x.DrawText("LOCAL IMAGE CACHE", font, Color.White, new PointF(10, 10));
    });
    
    using var ms = new MemoryStream();
    
    image.Save(ms, new RawEncoder());
    
    var dicomPixelData = DicomPixelData.Create(dicomFile.Dataset, true);
    dicomPixelData.AddFrame(new MemoryByteBuffer(ms.ToArray()));
    
    dicomFile.Dataset.AddOrUpdate(DicomTag.PhotometricInterpretation, PhotometricInterpretation.Monochrome2.Value);
    dicomFile.Dataset.AddOrUpdate(DicomTag.BitsAllocated, (ushort)16);
    dicomFile.Dataset.AddOrUpdate(DicomTag.BitsStored, (ushort)16);
    dicomFile.Dataset.AddOrUpdate(DicomTag.HighBit, (ushort)15);
    dicomFile.Dataset.AddOrUpdate(DicomTag.RescaleSlope, (decimal)1.0);
    dicomFile.Dataset.AddOrUpdate(DicomTag.RescaleIntercept, (decimal)0);
    dicomFile.Dataset.AddOrUpdate(DicomTag.WindowWidth, (decimal)ushort.MaxValue);
    dicomFile.Dataset.AddOrUpdate(DicomTag.WindowCenter, (decimal)(ushort.MaxValue - 1) / 2);
    dicomFile.Dataset.AddOrUpdate(DicomTag.SamplesPerPixel, (ushort)1);

    var adaptedFileName = dicomFile.File.Name.Replace(".dcm", "-lic.dcm");

    Console.WriteLine("Writing " + adaptedFileName);
    
    dicomFile.Save(adaptedFileName);
    
    Console.WriteLine("Done");
}
Console.WriteLine("All done");