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dcmjs-org / dcmjs

Javascript implementation of DICOM manipulation
https://dcmjs.netlify.com/
MIT License
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ignorePixelData #181

Closed Ouwen closed 3 years ago

Ouwen commented 3 years ago

In some situations the user may be only interested in the metadata from a dicom and would like to ignore the values from a pixel data tag.

swederik commented 3 years ago

This might be another option: https://github.com/dcmjs-org/dcmjs/pull/134

pieper commented 3 years ago

Yes, I think I like the more general stopAfterTag and untilTag. PixelData is almost always the last tag, but in case it isn't is there a case for skipping past it?

Ouwen commented 3 years ago

I like the #134 API using untilTag for arbitrary tags.

The main use case I have is for users performing partial read of a dicom file over network. A 5kb request will likely read the DICOM metadata header and part of the pixel data. If no pixel data is found more bytes can be requested until some max size or the end of the file. In this case the pixel data byte stream will be cut at some arbitrary length. We would simply want to check for pixelDataTag existence as a stop, without needing to read the values.

In an ideal world, DICOM would have a metadata tag that points to when metadata bytes end. I'm not a dicom expert so I'm not sure if such a tag exists.

The two features for the network partial read use case would require the following:

  1. some flag for the user as to whether the untilTag option is triggered
  2. Avoid reading the values from the untilTag which may throw an error for an early stream termination and result in unnecessary work

Regarding 2. I think the readTag function would have to be intercepted to avoid doing work below: https://github.com/dcmjs-org/dcmjs/blob/b17ea9ab8205590d24f55374cf16dcd43c0b7f40/src/DicomMessage.js#L139-L197

pieper commented 3 years ago

That sounds like a reasonable scenario. Do you think you could integrate that with https://github.com/dcmjs-org/dcmjs/pull/149 to handle that use case?

Ouwen commented 3 years ago

Sure happy to help make a PR. Regarding #149, we could add an ignoreValue option in addition to the untilTag. Then the flag will be existence of the untilTag in the dicom dict.

Ouwen commented 3 years ago

Closing due to #134 thanks @whatwilliam @pieper