jimp-dev/jimp

16 bit tiff does not convert properly

Open

#806 建立於 2019年10月19日

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 (3 留言) (1 反應) (0 負責人)JavaScript (13,218 star) (785 fork)batch import
bughelp wanted

描述

Expected Behavior

one to one conversion from 16 bit tiff to (presumably) 8 bit jpg

Current Behavior

Images that look like this:

image

this is supposed to be an X-Rite color passport, a piece of equipment for color calibration, on a poorly lit but supposedly white background:

image

Failure Information (for bugs)

It seems like the 16 bit tiff data is getting processed as 8 bit data, I don't know if it's throwing away the top byte in each two-byte pair, or whether it's pretending a single 16 bit value is actually two consecutive single byte values, but it's definitely very wrong.

Steps to Reproduce

  1. Generate a 16 bit TIFF image in any random image editor (photoshop, gimp, what have you)
  2. Make Jimp convert it to jpeg (either with write or getBuffer etc)

Context

This might be an example of #664

  • Jimp Version: 0.8.5
  • Operating System: Win10 x64
  • Node version: 12

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。
needs investigation
前置要求
Node.jsJavaScriptImage processing concepts
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。
40
研究方向
Investigate the TIFF decoder in jimp, likely in the jimp/src/tiff or similar directory. The issue suggests that 16 bit data is truncated to 8 bit. Look for how the bit depth is read from the TIFF header and how pixel data is processed. Check if there is a conversion step that assumes 8 bit. Also review linked issue #664 for context. Ensure that for 16 bit TIFF, the data is properly reduced to 8 bit for JPEG output, or that the library handles higher bit depths correctly.