Add section on checking for offset table in remote blob

[CPBridge]

No description provided.

[fedorov]

Chris will review again if tag length should be checked https://dicom.nema.org/medical/dicom/current/output/chtml/part05/sect_A.4.html#table_A.4-2

[CPBridge]

@fedorov @dclunie I believe this is resolved now. Now the code:

• Uses dcmread with stop_before_pixels=True to read until the start of the pixel data tag
• Read the 4 byte pixel data tag, check it has the expected value
• Skip 8 bytes total for the VR (2 bytes), 2 reserved bytes, and pixel data length (4 bytes)
• Read 4 byte item tag, check it has the expected value
• Read next 4 bytes (offset table item length), check whether it is non-zero to determine the presence of a BOT

[CPBridge]

Just wanted to nudge on this @fedorov @dclunie so it doesn't get lost. If the above approach for determining whether an image has an offset table is correct, we can merge

[fedorov]

Thanks for the nudge! I added to the agenda to discuss tomorrow.

[fedorov]

Chris, @dclunie did not have any questions about this.

Can you add pointers to the samples that cover each of the cases so we can have it for the reference and make testing easier?

[CPBridge]

@fedorov I added three examples to the snippet, one with no offset table, one with a basic offset table, and one with an extended offset table