String conversions to EncapsulateMetaData should attempt to be lossless.

[hjmjohnson]

Description

@seanm noted in #3242

Lossless would indeed be better. Searching the codebase, I see things like itk::EncapsulateMetaData(metaDict, "TestDouble", metaDataDouble); elsewhere... I was mostly copying nearby code, I wonder why itkNiftiImageIO is only using strings...?

Expected coding style

Avoid binary to string lossy behavior when using the meta data dictionary.

Actual coding style

Some places convert without using NumberToString{}(value).

Versions

It appears to be present from the origin of ITK.

[hjmjohnson]

@kian-weimer This is a nice issue that you could address after the python typehints are fixed.

[seanm]

@hjmjohnson are you suggesting to:

1. continue to encode as strings, but at least make them lossless
2. encode them directly as floats, not as strings at all.

The second choice would of course have backwards compatibility issues... but would probably be better if we were starting from scratch...

[hjmjohnson]

I would prefer that we encode them directly as primitive types (floats/double/ints...). In cases where strings might be necessary, we should use NumberToString{}(value).

[seanm]

If we go that route, what's the backwards compatibility plan?

[hjmjohnson]

I would recommend changing the key words for the meta data dictionary, and adding both a string version (in the present form) and the primitive stored version.

[seanm]

Right; seems reasonable.