On Thu, 2 Jan 2025 06:49:19 GMT, Jeremy <d...@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 one additional commit 
> since the last revision:
> 
>   8160327: fixing typo so `thumbnailPos` can be zero
>   
>   The `thumbnailLength` cannot be zero, but the position can be.

> 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 [...].

Note that the `DateTime` value extracted by 
`ExifMarkerSegment.getImageCreationTime` is that of the primary image, not the 
thumbnail. This is included to support the `ImageCreationTime` element of the 
Image I/O Standard Metadata Format Specification `javax_imageio_1.0`.

For reference see the [Exif 3.0 
specification](https://iptc.org/news/exif-3-0-released-featuring-utf-8-support),
 although the code from 2016 was based on Exif 2.x. The sections most pertinent 
to thumbnails are:

- 4.5.8 Basic Structure of Thumbnail Data
- 4.6.9.2 Thumbnail (1st IFD) Support Levels

>From section 4.6.9.2 in particular, there does not appear to be any 
>thumbnail-specific metadata worth extracting.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/22898#issuecomment-2659934595
PR Comment: https://git.openjdk.org/jdk/pull/22898#issuecomment-2659938631

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