jimp-dev/jimp

when rotate, the width and height of pic gets larger

Open

#808 建立於 2019年10月25日

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

描述

When I call roatet serval on the same object, the width and height of pic gets larger. after call rotate about 10 times, the pic will have a quiet obvious black border.

The follwoing code:

Jimp.read('https://s3-us-west-2.amazonaws.com/s.cdpn.io/123941/koala.jpg', (error, lenna) => {
        if (error) throw error;
        lenna
          .rotate(90)
          .rotate(90)
          .rotate(90)
          .rotate(90)
          .rotate(90)
          .rotate(90)
          .rotate(90)
          .getBase64(Jimp.AUTO, (err, base64) => {
            this.imageRef.setAttribute('src', base64);
          });
      });

Expected Behavior

The pic rotate with the original width and height.

Current Behavior

the pic will have black border ,the width and height of pic will grow evey time.

Context

  • Jimp Version: ^0.8.5
  • Operating System: win10
  • Node version: v10.16.3

貢獻者指南

技術棧
javascript
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。
2
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
JavaScriptJimp basics
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。
70
研究方向
Investigate the `rotate` method in Jimp's source code (likely in the image manipulation module). The issue suggests that successive rotations increase the image dimensions instead of preserving them. Look for how the rotation is implemented, especially the calculation of output dimensions and any cropping logic. Check if each rotation accumulates the black border due to off center rotation or incorrect dimension handling. Consider adding a fix that ensures the output size remains constant when rotating by multiples of 90 degrees, or cropping to original dimensions after rotation.