jimp-dev/jimp

Resizing an image with transparency

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#442 建立於 2018年4月26日

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 (4 留言) (4 反應) (0 負責人)JavaScript (13,218 star) (785 fork)batch import
bughelp wantedsolution in issue

描述

Hy guys ! I have a little problem and I can not find answers. When I try to resize a picture with transparency I get a border between transparency and the other color. On white you can see the border really clear on other colors not so much, but is there.

If I use RESIZE_NEAREST_NEIGHBOR the transparent image looks okay, but the quality of other pictures is poor. If I use the other ones I end up with a picture with a border between transparency and color. Do you have any idea ? Any advices ? Thank you !

Original picture: label

Resized picture with RESIZE_BEZIER logo-1083

貢獻者指南

技術棧
javascriptnodejs
領域
backend
議題類型
bug
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
3
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
half day
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
stale
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
clear
前置要求
Understanding of image resizing algorithmsFamiliarity with alpha compositingJavaScript knowledgeBasic usage of jimp
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
35
研究方向
Investigate the resizing methods in jimp (likely in src/image/resize.js or similar). The issue arises because interpolation algorithms like Bezier or bilinear blend pixel values without considering the alpha channel, causing a dark/light border. A common fix is to premultiply alpha before resizing and then reverse. Check existing comments for any hints from maintainers. Test with the provided images to confirm the fix.