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Posted to dev@tika.apache.org by "dschmidt (via GitHub)" <gi...@apache.org> on 2026/10/07 17:24:39 UTC
[PR] TIKA-4936: write the largest image of an icon group first [tika]
dschmidt opened a new pull request, #3309:
URL: https://github.com/apache/tika/pull/3309
Follow-up to the PE icon extraction in TIKA-4936.
An `.ico` holds several images of the same icon at different sizes, and a reader that takes it for a multi-page image hands out the first entry. The order a resource compiler wrote carries no meaning - Windows looks up the size it needs via `LookupIconIdFromDirectoryEx` rather than reading in order - so whoever renders the first entry gets an arbitrary size. Of the four binaries I looked at, two list their icons ascending and two descending:
```
snoretoast.exe 16x16 24x24 32x32 48x48 96x96 256x256
opencloud.exe 16x16 24x24 32x32 48x48 64x64 128x128 256x256
mfc140.dll 32x32 16x16
mfc140u.dll 32x32 16x16
```
A thumbnailer that asks a generic image library for the extracted icon therefore renders a 16 pixel image and scales it up, even though the group carries a 1024 pixel PNG.
`buildIco` now writes the entries by descending pixel count, then colour depth. The size comes from the image itself rather than from its directory entry: an entry holds one byte per side and reads 0 for 256 or above, so a 1024 pixel PNG and a 256 pixel bitmap are indistinguishable there. The images themselves are copied verbatim as before.
The round-trip tests compared the rebuilt file to the `.ico` the resources were compiled from, which no longer holds byte for byte. They now compare against `-rebuilt.ico` fixtures that hold the same images in the new order, and `testLargestIconComesFirst` pins the order itself.
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Re: [PR] TIKA-4936: write the largest image of an icon group first [tika]
Posted by "tballison (via GitHub)" <gi...@apache.org>.
tballison commented on PR #3309:
URL: https://github.com/apache/tika/pull/3309#issuecomment-6044507708
My :robot: says :+1:
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Re: [PR] TIKA-4936: write the largest image of an icon group first [tika]
Posted by "dschmidt (via GitHub)" <gi...@apache.org>.
dschmidt commented on PR #3309:
URL: https://github.com/apache/tika/pull/3309#issuecomment-6045935651
Great! Thanks for dealing with all my weird oddly specific PRs 😄
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Re: [PR] TIKA-4936: write the largest image of an icon group first [tika]
Posted by "tballison (via GitHub)" <gi...@apache.org>.
tballison merged PR #3309:
URL: https://github.com/apache/tika/pull/3309
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Re: [PR] TIKA-4936: write the largest image of an icon group first [tika]
Posted by "dschmidt (via GitHub)" <gi...@apache.org>.
dschmidt commented on PR #3309:
URL: https://github.com/apache/tika/pull/3309#issuecomment-6044597033
> My 🤖 says 👍
good guy 🤖
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