/// <summary>
/// Fills the <see cref="OverlayData"/> property with the overlay(s) that had been encoded
/// in the <see cref="DicomTags.PixelData"/> of the SOP Instance. If the image is a
/// multi-frame, overlay data is extracted from all the frames.
/// </summary>
/// <param name="pd">The pixel data that contains the encoded overlay(s).</param>
/// <exception cref="DicomException">Thrown if <paramref name="pd"/> is not a valid source of embedded overlay data.</exception>
/// <returns>True if the <see cref="OverlayData"/> was populated with data encoded in the pixel data; False if <see cref="OverlayData"/> is not empty.</returns>
public unsafe bool ExtractEmbeddedOverlay(DicomUncompressedPixelData pd)
{
byte[] overlayData = this.OverlayData;
if (overlayData != null && overlayData.Length > 0)
{
return(false);
}
// General sanity checks
if (pd.SamplesPerPixel > 1)
{
throw new DicomException("Unable to convert embedded overlays when Samples Per Pixel > 1");
}
if (pd.BitsStored == 8 && pd.BitsAllocated == 8)
{
throw new DicomException("Unable to remove overlay with 8 Bits Stored and 8 Bits Allocated");
}
if (pd.BitsStored == 16 && pd.BitsAllocated == 16)
{
throw new DicomException("Unable to remove overlay with 16 Bits Stored and 16 Bits Allocated");
}
if (OverlayBitPosition <= pd.HighBit && OverlayBitPosition >= pd.LowBit)
{
throw new DicomException(String.Format("Invalid overlay bit position ({0}); overlay would be in the middle of the pixel data.", OverlayBitPosition));
}
int frameSize = pd.UncompressedFrameSize;
int overlayDataLength = (int)Math.Ceiling((frameSize * pd.NumberOfFrames) / (pd.BitsAllocated * 1d));
int frameLength = frameSize / pd.BytesAllocated;
// Ensure even length overlay
if (overlayDataLength % 2 == 1)
{
overlayDataLength++;
}
overlayData = new byte[overlayDataLength];
int overlayOffset = 0;
byte overlayMask = 0x01;
if (pd.BitsAllocated <= 8)
{
var embeddedOverlayMask = ((byte)(0x1 << OverlayBitPosition));
// Embededded overlays must exist for all frames, they can't be for a subset
for (int i = 0; i < pd.NumberOfFrames; i++)
{
byte[] frameData = pd.GetFrame(i);
ExtractEmbeddedOverlay(frameData, frameLength, embeddedOverlayMask, overlayData, ref overlayOffset, ref overlayMask);
pd.ReplaceFrame(i, frameData);
}
}
else
{
var embeddedOverlayMask = ((ushort)(0x1 << OverlayBitPosition));
// Embededded overlays must exist for all frames, they can't be for a subset
for (int i = 0; i < pd.NumberOfFrames; i++)
{
byte[] frameData = pd.GetFrame(i);
ExtractEmbeddedOverlay(frameData, frameLength, embeddedOverlayMask, overlayData, ref overlayOffset, ref overlayMask);
pd.ReplaceFrame(i, frameData);
}
}
// Assign the new overlay tags
this.OverlayBitPosition = 0;
this.OverlayBitsAllocated = 1;
if (this.IsBigEndianOW)
{
// Just do a bulk swap, performance isn't much of an issue.
ByteBuffer buffer = new ByteBuffer(overlayData, Endian.Little);
buffer.Swap2();
this.OverlayData = buffer.ToBytes();
}
else
{
this.OverlayData = overlayData;
}
// Cleanup Rows/Columns if necessary
if (this.OverlayColumns == 0)
{
this.OverlayColumns = pd.ImageWidth;
}
if (this.OverlayRows == 0)
{
this.OverlayRows = pd.ImageHeight;
}
return(true);
}