jimp-dev/jimp

16 bit tiff does not convert properly

Open

#806 opened on Oct 19, 2019

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 (3 comments) (1 reaction) (0 assignees)JavaScript (13,218 stars) (785 forks)batch import
bughelp wanted

Description

Expected Behavior

one to one conversion from 16 bit tiff to (presumably) 8 bit jpg

Current Behavior

Images that look like this:

image

this is supposed to be an X-Rite color passport, a piece of equipment for color calibration, on a poorly lit but supposedly white background:

image

Failure Information (for bugs)

It seems like the 16 bit tiff data is getting processed as 8 bit data, I don't know if it's throwing away the top byte in each two-byte pair, or whether it's pretending a single 16 bit value is actually two consecutive single byte values, but it's definitely very wrong.

Steps to Reproduce

  1. Generate a 16 bit TIFF image in any random image editor (photoshop, gimp, what have you)
  2. Make Jimp convert it to jpeg (either with write or getBuffer etc)

Context

This might be an example of #664

  • Jimp Version: 0.8.5
  • Operating System: Win10 x64
  • Node version: 12

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.
half day
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.
needs investigation
Prerequisites
Node.jsJavaScriptImage processing concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Investigate the TIFF decoder in jimp, likely in the jimp/src/tiff or similar directory. The issue suggests that 16 bit data is truncated to 8 bit. Look for how the bit depth is read from the TIFF header and how pixel data is processed. Check if there is a conversion step that assumes 8 bit. Also review linked issue #664 for context. Ensure that for 16 bit TIFF, the data is properly reduced to 8 bit for JPEG output, or that the library handles higher bit depths correctly.