RFR: 8160327: Support for thumbnails present in APP1 marker for JPEG [v3]

[Brian Burkhalter]

On Fri, 21 Feb 2025 02:31:42 GMT, Jeremy <duke at openjdk.org> wrote:

>> This adds support for parsing thumbnails in an APP1 Exif marker.
>> 
>> This builds on an unfinished proposal by Brian Burkhalter (around 2016). In that previous work the only additional meta info he parsed was the image creation time; this PR similarly includes the same property. (I can't speak to why he included that property, but it looks like he has a lot of experience with ImageIO so I trust his judgment.)
>> 
>> The test addresses the original images attached to the ticket plus a few extra images I found on my computer that include unusual properties. (Possibly those images are malformed, but if they exist in the wild and other platforms support them then I'd prefer to support them too.)
>
> Jeremy has updated the pull request incrementally with four additional commits since the last revision:
> 
>  - 8160327: alphabetize imports
>    
>    This is in response to:
>    https://github.com/openjdk/jdk/pull/22898#discussion_r1956718373
>  - 8160327: fallback to using MarkerSegment if ExifMarkerSegment fails
>    
>    This is in response to:
>    https://github.com/openjdk/jdk/pull/22898#discussion_r1955194737
>    
>    "I would have supposed that if there's an Exif segment we don't like it would be best to just act like the segment isn't there."
>  - 8160327: include support for JFIF *and* EXIF thumbnails together
>    
>    This is in response to:
>    https://github.com/openjdk/jdk/pull/22898#issuecomment-2666324177
>    
>    As mentioned here ( https://github.com/openjdk/jdk/pull/22898#issuecomment-2666949882 ) we'll need to update some documentation about thumbnails.
>  - 8160327: moving test + resources to separate directory
>    
>    This is in response to:
>    https://github.com/openjdk/jdk/pull/22898#issuecomment-2657721887

The code changes now look good. I've not looked at the test yet but I see that it's been put in its own directory along with the images which is good. I don't think that the images need the `jdk_8160327` prefix however.

Has it been determined which of these images can legitimately be included, aside from SV650?

Also, as I mentioned before, I think that the JPEG metadata specification will need to slightly updated to cover the modified thumbnail behavior. This change will require a CSR.

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PR Comment: https://git.openjdk.org/jdk/pull/22898#issuecomment-2675396159