jimp-dev/jimp

Efficient clone + crop (or contain)

Open

#847 opened on Feb 24, 2020

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

Description

Expected Behavior

Working on a Video Stream at 15fps I need to crop a part of each frame then resize it into a canvas using crop() or contain() that use crop underlaying

Current Behavior

It works but it use about 100ms to process a 720P video.

Failure Information (for bugs)

Not sure if it's a bug or a feature.

Actually I have to perform img.clone().crop() whereas it might be more efficient to add an option to crop() into a new image (the code would gather only the relevant pixels) ?

Contributor guide

Tech stack
javascriptnodejs
Domain
backend
Issue type
feature
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.
clear
Prerequisites
Understanding of Jimp's image data structureFamiliarity with Buffer operations in Node.js
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65
Research direction
Examine the current crop() implementation in Jimp (likely in packages/core/src/image/crop.js). The goal is to add an option to crop() that directly creates a new image containing only the cropped pixels, avoiding the memory and time overhead of cloning the entire image first. Study how Jimp stores pixel data (RGBA buffer) and how the clone() method works to understand the current bottleneck. Then implement a modification that, when an optional parameter (e.g., 'clone: false') is provided, copies only the relevant pixel region into a new Jimp instance. Test performance with a sample 720p video frame.