[Dcmlib] Fwd: Overlay in DataSet CompressedSamples^RG3

[Mathieu Malaterre]

---------- Forwarded message ----------
From: Mathieu Malaterre <mathieu.malate... at gmail.com>
Date: Jan 4, 3:15 pm
Subject: Overlay in DataSet CompressedSamples^RG3
To: comp.protocols.dicom


hi,

  Since the early beginning of GDCM we have always been 'cleaning up'
the unused bits of the Pixel Data just in case an overlay would be
found.
  This is extremely time consuming, and I was running some test to
check if I could simply run the cleanup only when a 0x60xx element was
to be found. It works on all but one gdcmData files we have been
gathering.

  the only exception is the Dataset CompressedSamples^RG3, from the
compressed jpeg in WG04, see file

 ftp://medical.nema.org/medical/dicom/DataSets/WG04/compsamples_jpeg.tar
  ->  IMAGES/JPLY/RG3_JPLY
(1.3.6.1.4.1.5962.1.1.11.1.5.20040826185059.5457)

  Clearly the DataSet does not declare any Overlay, but still one
cannot simply load the dataset without cleaning up the unused bit.
   When loading the image, the IJG (the jpeg lib used in GDCM) is
complaining about

  "Invalid SOS parameters for sequential JPEG"

  I am wondering if the artefact I am seeing is not simply due to a
poor jpeg encoding in which case I could detect that instead of
looping over the whole image in quest for a potential artefact.

* TomoVision is apparently using the PVRG jpeg lib and has the exact
same artefact as we do (a bright spot in the center right image).
* DicomWorks is not properly displaying the image, but does not show
the artefact.
* IrfanView is simply crashing.

Thanks for comments
-Mathieu