For grayscale images, fo-dicom by default applies the rendering options available in the DICOM dataset when rendering the actual image with DicomImage.RenderImage. By default, the rendering options identifies whether the colors should be displayed using the Monochrome1 or Monochrome2 color tables. To override this color scheme, the following workarounds are available.

The Color32[] property GrayscaleColorMap has been added to the DicomImage class. By default, the color map is selected based on the Photometric Interpretation of the associated dataset (Monochrome 1 or 2), but it can be set to any 256 item Color32 array prior to rendering the image.

Example of applying arbitrary color map and then render image:

    var di = new DicomImage(dicomFileName);
    di.GrayscaleColorMap = ColorTable.LoadLUT(lutFileName);
    var image = di.RenderImage();

The lutFileName has to reference a binary file, with 768 bytes length. It has to contain the 3 bytes (red, green blue) for all 256 possible values.

By default, grayscale images are rendered via the Monochrome1 or Monochrome2 color tables:

To override this selection upon rendering, for example using a color table loaded from file via ColorTable.LoadLUT or by composing a 256 item Color32 array, the following helper method can be applied to create an LUT that simultaneously accounts for the image properties specified in the dataset:

    public static ILUT CreateFromDataset(DicomDataset dataset, Color32[] colorTable)
    {
      var options = GrayscaleRenderOptions.FromDataset(dataset, 0);

      var composite = new CompositeLUT();
      OutputLUT output;

      if (options.RescaleIntercept != 0.0 || options.RescaleSlope != 1.0)
      {
        composite.Add(new ModalityLUT(options));
      }

      composite.Add(VOILUT.Create(options));
      composite.Add(
        output =
        new OutputLUT(colorTable ?? (options.Monochrome1 ? ColorTable.Monochrome1 : ColorTable.Monochrome2)));

      if (options.Invert)
      {
        composite.Add(new InvertLUT(output.MinimumOutputValue, output.MaximumOutputValue));
      }

      return new PrecalculatedLUT(composite, options.BitDepth.MinimumValue, options.BitDepth.MaximumValue);
    }

Creating a composite LUT using a non-monochrome color table such as the "green-fire-blue" color scheme and rendering the same image via the ImageGraphic.RenderImage(ILUT) method would then yield the following result: