jimp-dev/jimp

Efficient clone + crop (or contain)

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#847 创建于 2020年2月24日

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 (0 评论) (0 反应) (0 负责人)JavaScript (13,218 star) (785 fork)batch import
enhancementhelp wanted

描述

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) ?

贡献者指南

技术栈
javascriptnodejs
领域
backend
议题类型
feature
难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。
3
预计时间有经验贡献者完成调查、实现、测试并准备 pull request 的粗略时间范围。
1-3 hours
活动状态议题当前的可参与程度：新鲜、活跃、陈旧、阻塞或等待维护者输入。
stale
清晰度议题是否清楚说明期望改动、验收标准和下一步。
clear
前置要求
Understanding of Jimp's image data structureFamiliarity with Buffer operations in Node.js
新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。
65
研究方向
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.