We use `Math.ceil()` at 2 places in BMPImageWriter and both of them are under encodeRLE4() function. Also they are used only under absolute mode of encoding.
First usage `(int)Math.ceil((absVal-1)/2)` is while encoding data in each scanline. Here absVal always starts with 3 and increments by 2, so `Math.ceil()` is basically a no-op here and its usage can be removed. Second usage `(int)Math.ceil((absVal+1)/2)` is while encoding end of scanline data. Here absVal can be even and we need to use `Math.ceil()` properly otherwise padding will not be added properly. I have added regression test which actually identifies this issue and it creates a corrupt encoded BMP image. In this regression test we have odd number of distinct pixels at the end of scanline and encoding without proper padding corrupts next scanline of data. --------- - [x] I confirm that I make this contribution in accordance with the [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). ------------- Commit messages: - Update test message - Add test, remove ceil() and floating point usage - 8384512: BMPImageWriter uses integer division before Math.ceil causing incorrect calculation Changes: https://git.openjdk.org/jdk/pull/31447/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=31447&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8384512 Stats: 114 lines in 2 files changed: 112 ins; 0 del; 2 mod Patch: https://git.openjdk.org/jdk/pull/31447.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/31447/head:pull/31447 PR: https://git.openjdk.org/jdk/pull/31447
