Decode leica barcode

[malaterre]

It would be nice if the barcode from leica (*.scn) would be decoded (much easier to read).

Eg:

$ tiffinfo Leica-1.scn| grep barcode
MDQwNTA2MjlD
$ echo MDQwNTA2MjlD | base64 -d
04050629C%

The following line would need to be adapted:

// Get barcode as stored in 2010/10/01 namespace
collection->barcode = _openslide_xml_xpath_get_string(ctx, "/d:scn/d:collection/d:barcode/text()");

Thanks !

[bgilbert]

Argh, I hadn't realized the barcode was a Base64-encoded string. Thanks for the report.

Fixing this will break compatibility with applications using that property. The alternatives are worse (adding leica.decoded-barcode, or documenting the property as Base64-encoded), but perhaps we need to make it easier for applications to implement compatibility workarounds for particular versions of OpenSlide.

Also, update the website to document that older versions Base64-encode the property.

[malaterre]

I personnally like the leica.decoded-barcode solution, what if tomorrow a vendor start storing a barcode as QR code. It would make sense for openslide to provide both the barcode and the decoded one.

my 2cts

[bgilbert]

I'm not sure I understand your point. If the QR code is stored as pixels, we would expose it in the label associated image, as we do now for several formats. If the contents of the QR code are stored, we would expose them as a string or numeric property. How would a Base64-encoded property help anyone?

In any event, leica.barcode is a vendor-specific property, so we don't need to be concerned with other vendors here.

[bgilbert]

Also, you said:

The following line would need to be adapted:

// Get barcode as stored in 2010/10/01 namespace
collection->barcode = _openslide_xml_xpath_get_string(ctx, "/d:scn/d:collection/d:barcode/text()");

Do you have evidence that the 2010/03/10 namespace doesn't also Base64-encode the barcode?

[malaterre]

Without specifications or actual dataset I cannot answer. I simply assumed that barcode was encoded in base64 (which proved correct so far for the 2010 ns one).

[malaterre]

The terminology I used for decoded was an opaque transformation from the stored representation to a human readable representation (eg. QR code string -> QR decoded string, or base64 -> decoded string). It is very vague and mostly academic debate since it was only a (poor) example to find a solution to the leica.barcode vs leica.decoded-barcode initial issue.

[bgilbert]

OK, thanks for the clarifications.

[bgilbert]

Fixed for 2010/10/01 namespace only. The 2010/03/10 namespace puts the barcode in a different place and I don't have any evidence on whether it is also Base64-encoded, so I haven't changed how those slides are handled. If anyone has a 2010/03/10 slide with a barcode and can verify whether or not the barcode attribute is Base64-encoded, please comment here.