jimp-dev/jimp

Resizing an image with transparency

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#442 opened on Apr 26, 2018

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 (4 comments) (4 reactions) (0 assignees)JavaScript (785 forks)batch import
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Description

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

Contributor guide

Research direction
Examine the resize functions in Jimp to understand how alpha transparency is handled during interpolation. Focus on the difference between nearest neighbor and other interpolations. Investigate if premultiplied alpha is used and adjust the resize algorithm accordingly.
Tech stack
javascript
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.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
JavaScriptGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70