RFR: 8365467: Fix multiple issues in ExplodedImage

Wed Aug 13 12:26:55 UTC 2025

This PR addresses several issues found while adding unit tests for ExplodedImage.
I have added review comments for changes (some of which are a little preferential, but bring the code into line with things like ImageReader in terms of the name choices for variables).
Later it is likely that this code will be adapted for the up-coming preview mode support in Valhalla, so having it unit-testable is important.

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Commit messages:
 - Provisional fixes for ExplodedImage issues.

Changes: https://git.openjdk.org/jdk/pull/26757/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26757&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365467
  Stats: 371 lines in 5 files changed: 291 ins; 27 del; 53 mod
  Patch: https://git.openjdk.org/jdk/pull/26757.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26757/head:pull/26757

PR: https://git.openjdk.org/jdk/pull/26757