Artwork from NSMetadataItem

General
1

I need to convert the NSData object from an NSMetadataItem object into a picture. The keyword is “artwork” and I can see the data as a MemoryBlock, but can’t figure out how to make that final conversion. Any clues?

This is what the data looks like:

2

The first part is a binary plist and then jpeg data at first glance.

3

That is, it looks like it’s a binary plist file with a child containing the image data in a jpeg data blob.

4

What did you do with NSMetadataItem to get that plist data?
Should the methods there not give you the NSData object of the JPEG directly?

5

Are you sure this isn’t an NSDictionary? Perhaps you’ve called valuesForAttributes (returns an NSDictionary) instead of valueForAttribute (returns am object)

6

Isn’t a plist an XML document?

7

I’ve implemented in MacOSLib both AVAsset and AVMetaDataItem. I create the AVAsset from the file, then get the metadata formats through availableMetadataFormats. For the first format (just to keep it simple), I get an array of AVMetadataItems using metadataForFormat.

For each AVMetadataItem in the array, I get the key (as string) and commonValue (as string). This works. If the key =“artwork”, I pull the dataValue (NSData). It’s that object that I posted above, and where I am stuck.

8

In this case, it’s a binary plist (bplist00). While it is a type of XML, it’s converted to binary to use less space.

@Kem Tekinay - It appears to be a JPEG, but there are elements of the first segment that do not match the JFIF spec. Scan through the rest of the data and see if you find the following sequence:

'FF', 'D8', 'FF', 'E0', <2 bytes to be skipped>, "JFIF", '00'
9

First I should mention that @Justin Elliott was right, it’s a plist, and I was able to extract its parts by converting it, ultimately, to a Dictionary. I’ll do it differently before I’m done, but for now I have four keys, data, identifier, picturetype, and MIME.

Tim, the data part starts with exactly those bytes, although, interestingly, picturetype is “other”. Now what?

(Keep in mind that I can’t use plugins for this.)

10

WAIT!! I had tried Picture.GetData and it didn’t work. BUT I forgot that I has hex-encoded the data for readability. I HAVE ARTWORK!!

Thanks to all for the help.