8000 Respect Buffer view bounds in fromBitmap and quantize by Shrusti-pk · Pull Request #1419 · jimp-dev/jimp · GitHub
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Respect Buffer view bounds in fromBitmap and quantize - #1419

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Shrusti-pk:buffer-view-bounds
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Respect Buffer view bounds in fromBitmap and quantize#1419
Shrusti-pk wants to merge 1 commit into
jimp-dev:mainfrom
Shrusti-pk:buffer-view-bounds

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@Shrusti-pk
@Shrusti-pk Shrusti-pk commented Oct 29, 2026
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What's Changing and Why

Jimp.fromBitmap() and the quantize plugin read data.buffer and ignore byteOffset/byteLength. Node serves small Buffers (under 4 KiB, from Buffer.from() or Buffer.allocUnsafe()) as slices of a shared 8 KiB pool, so .buffer is the whole pool, not the image.

  • fromBitmap: a Buffer also matches the Uint8Array branch, which overwrites the copy made just above it with Buffer.from(data.buffer). The bitmap then aliases the pool: pixels come from unrelated Buffers in the process, and writes to the image overwrite them.
  • quantize: image-q's PointContainer.fromUint8Array reads .buffer itself, so a bounded view is not enough and it now gets a copy. After a small crop() (which uses Buffer.allocUnsafe), quantize() built its palette from pool memory and returned an 8 KiB bitmap.

Repro on Node 22 before this change:

const secret = Buffer.from("SECRET-API-TOKEN-0123456789abcdef");
const pixels = Buffer.from([
  0xff, 0, 0, 0xff, 0xff, 0, 0, 0xff,
  0xff, 0, 0, 0xff, 0xff, 0, 0, 0xff,
]);
const image = Jimp.fromBitmap({ data: pixels, width: 2, height: 2 });

image.bitmap.data.length; // 8192, expected 16
image.bitmap.data.includes("SECRET-API-TOKEN"); // true
image.bitmap.data.fill(0x41);
secret.toString(); // "AAAAAAAA..."

What else might be affected

A Buffer passed to fromBitmap is now actually copied, as that branch intended, so editing the image no longer writes back into the caller's Buffer. Uint8Array/Uint8ClampedArray input is still wrapped without a copy, limited to the view's own bytes.

Tasks

  • Add tests
  • Update Documentation
  • Update jimp.d.ts
  • Add SemVer Label

The new tests fail before the change and pass after. pnpm build, pnpm lint, pnpm test and pnpm test:browser pass locally.

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