jimp-dev/jimp

[Bug] Weird BMP load bug

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#802 opened on Oct 5, 2019

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 (9 comments) (2 reactions) (0 assignees)JavaScript (13,218 stars) (785 forks)batch import
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Description

Expected Behavior

The copied bmp file should be exactly the same as the original one.

Current Behavior

For some reason for this bmp file content gets moved/shifted. It does not happen for all the bmp files.

Failure Information (for bugs)

Steps to Reproduce

I've created minial reproducible repo:

git git@github.com:elderapo/jimp-bmp-bug.git
cd ./jimp-bmp-bug
yarn
yarn start

Screenshots from.bmp to.bmp

Context

  • Jimp Version: ^0.8.4
  • Operating System: Ubuntu 14.04
  • Node version: v11.10.0, v12.10.0

Failure Logs

The loading system for bmp files seems to be broken. Exact same thing happens when reading bmp file from disk, buffer. Even when file is saved to a different format it still gets shifted.

Contributor guide

Tech stack
javascriptnodejs
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
basic JavaScriptimage format basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Reproduce the bug using the provided minimal reproducible repo. Examine Jimp's BMP decoder, likely in packages/plugin bmp or similar. Compare the original BMP file's pixel data with the output to identify the shift. Check if the issue is due to incorrect handling of BMP padding or color table. Test with different BMP files to confirm affected cases.