RFR: 8356137: GifImageDecode can produce opaque image when disposal method changes [v3]

[Jeremy Wood]

On Wed, 7 May 2025 02:58:01 GMT, Jeremy Wood <duke at openjdk.org> wrote:

>> This resolves a gif parsing bug where an unwanted opaque rectangle could appear under these conditions:
>> 
>> 1. The disposal method for frames is 1 (meaning "do not dispose", aka "DISPOSAL_SAVE")
>> 2. The transparent pixel is non-zero
>> 3. There's more than one such consecutive frame
>> 
>> Previously: the GifImageDecoder would leave the saved_image pixels as zero when they were supposed to be transparent. This works great if the transparent pixel index is zero, but it flood fills the background of your frame with the zeroeth color otherwise.
>
> Jeremy Wood has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - 8356120: updating (c) year
>  - 8356137: cleaning up error message

Closing for now; I want to focus on one PR at a time. I can reopen this after #25076 .

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PR Comment: https://git.openjdk.org/jdk/pull/25044#issuecomment-2881794176