[rayne]

Tiled data is like this:

[LeoDraco]

That would be a base64-encoded number, which is to say, that Tiled stores its data in a "safe" binary format: its data is converted such that its bytes, when interpreted by any program as ASCII text, fit within the normal ASCII character set. So, all that you would need to do is decode the base64 string, and properly interpret the resulting binary data.
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"...LeoDraco is a pompus git..." -- Mandrake

[rayne]

Thanks, I'll try it ASAP. After base64-decoding, should I gunzip it? Or is it raw tile ID array?

[white_door]

In the past tiled would default to compressing the layer data with gzip then base64ing it. Now I think it leaves it uncompressed and just base64s it by default.

Also you can now gzip the whole file, by saving with the .tmx.gz format. I found this to give better compression and was easier to decode when using zlib in C.

[Bjorn]

A reason for using layer data gzip compression would be to keep down the size of this part of the file, so that it remains easier to edit the file in a text editor or to keep it under version control in its basic form. You can do this in addition to using .tmx.gz.

Using the .tmx.gz scheme has the advantage of reducing file size even more as white_door pointed out. Loading it with libxml2 is very easy since it has built in support for gzip encoded files (though only when loading from disk as far as I know).