DicomImageReader and 12-bit monochrome images

[David Maffitt]

I am puzzled by org.dcm4che3.imageio.plugins.dcm.DicomImageReader's handling of Monochrome images (5.18.1)

In BufferedImage read(int frameIndex, ImageReadParam param), there is the fragment

        ColorModel cm;
        if (pmi.isMonochrome()) {
            int[] overlayGroupOffsets = getActiveOverlayGroupOffsets(param);
            byte[][] overlayData = new byte[overlayGroupOffsets.length][];
            for (int i = 0; i < overlayGroupOffsets.length; i++) {
                overlayData[i] = extractOverlay(overlayGroupOffsets[i], raster);
            }
            cm = createColorModel(8, DataBuffer.TYPE_BYTE);
            SampleModel sm = createSampleModel(DataBuffer.TYPE_BYTE, false);
            raster = applyLUTs(raster, frameIndex, param, sm, 8);
            for (int i = 0; i < overlayGroupOffsets.length; i++) {
                applyOverlay(overlayGroupOffsets[i],
                        raster, frameIndex, param, 8, overlayData[i]);
            }
        } else {
            cm = createColorModel(bitsStored, dataType);
        }
        return new BufferedImage(cm, raster , false, null);

This forces the data into 8-bits regardless of bitsStored.  Is this necessary/intentional?  We lose the original DataBuffer.TYPE_USHORT. This is a surprise for downstream pixel editing.

Dave

[Gunter Zeilinger]

You may use DicomImageReader.readRaster(..) instead DicomImageReader.read(..) and apply the Grayscale Transformations (Modality & VOI LUT) yourself.

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