jimp-dev/jimp

BMP image changes colour when loaded by JIMP

Open

#844 opened on Feb 7, 2020

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

Description

Expected Behavior

Colour of BMP image shouldn't change.

Current Behavior

The reds turn to green, and the blues turn to red.

Failure Information (for bugs)

Seems related to the endian of the BMP perhaps?

Steps to Reproduce

I have a replication of this bug in a code sandbox. After reading the bmp and turning it into a base64 it changes the colours. I've included the image in the sandbox.

https://codesandbox.io/s/angry-gauss-nnd63?fontsize=14&hidenavigation=1&theme=dark

Screenshots image

Context

We have a part of our application where users can upload their own images and apply filters to them. Some user images may be in BMP format.

  • Jimp Version: codesandbox's
  • Operating System: Windows 10
  • Node version: codesandbox's

Failure Logs

n/a

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
BMP file formatendiannessNode.js buffer handling
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
Investigate the BMP decoder in the Jimp source code, likely in `src/image/bmp.js`. The issue suggests an endianness problem when reading the BMP header and pixel data. Use the provided sandbox (https://codesandbox.io/s/angry gauss nnd63) to test changes. Compare the byte order for red, green, blue channels and verify against BMP specification. Check if the BMP version (e.g., BITMAPINFOHEADER) affects the color order.