Automattic/node-canvas

Black CMYK JEPGs in PDF with MIME data mode

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#1,183 建立於 2018年6月21日

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BugHelp wantedImages & Formats: JPEG

描述

Bug

I want to embed cmyk images in pdf using img.dataMode = Image.MODE_MIME. That should take the image and embed it into pdf without any painting or editing. But all cmyk images are black.

JPG img

PDF

Files img.jpg.zip out.pdf

Related issue https://github.com/Automattic/node-canvas/issues/425

Steps to Reproduce

const { createCanvas, Image } = require("canvas")
const { writeFileSync, readFileSync } = require("fs")

const img = new Image()
img.dataMode = Image.MODE_MIME
img.src = readFileSync("img.jpg")

const canvas = createCanvas(200, 200, "pdf")
const ctx = canvas.getContext("2d")
ctx.drawImage(img, 50, 50, 100, 100)
writeFileSync("out.pdf", canvas.toBuffer())

Your Environment

  • Version of node-canvas: 2.0.0-alpha.12
  • Environment: node 10.1.0, macOS 10.13.5

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。
4
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。
1-2 days
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
Node.jsnode canvas 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。
25
研究方向
Investigate the MODE MIME handling for JPEG images in node canvas, particularly the color space conversion from CMYK to device dependent colors. Examine the native code in src/Image.cc and src/JPEGMarker.h for how JPEG data is passed to Cairo and PDF backend. Also look at the PDF generation logic in src/PDFStream.h. The related issue #425 (https://github.com/Automattic/node canvas/issues/425) may provide background on similar issues. Check if the CMYK JPEG needs a color space transformation before embedding in PDF, or if the MODE MIME path is missing a color space tag.