jimp-dev/jimp

Dark Diff

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#887 opened on May 15, 2020

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

Description

Expected Behavior

Dark backgrounds when diffing images together instead of the opaque light background

Current Behavior

The backgrounds still appear light

Failure Information (for bugs)

A diff with a white opaque background is produced

Steps to Reproduce

const snapshotA = await Jimp.read(fileA)
snapshotA.background(0x00000000)

const snapshotB = await Jimp.read(fileB)
snapshotB.background(0x00000000)

const diff = Jimp.diff(snapshotA, snapshotB, mismatchThreshold)

Screenshots

Context

  • Jimp Version: 0.10.3
  • Operating System: Mac OS Catalina 10.15.3
  • Node version: v10.18.1

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.
clear
Prerequisites
Familiarity with Jimp APIUnderstanding of image blending
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
The issue is about the background color in image diffs. Look at the `Jimp.diff` function implementation to understand how the diff image is composited. Check how the background color of input images is used in the diff result. The user provides images with transparent background but the diff overlay still uses white. Investigate the diff algorithm and see if it uses a hardcoded white background or if it should blend with the source images' backgrounds. Files to examine: likely in packages/diff/src/index.js or similar. Review any maintainer comments if present.