Automattic/node-canvas

Black CMYK JEPGs in PDF with MIME data mode

Open

#1183 opened on Jun 21, 2018

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BugHelp wantedImages & Formats: JPEG

Description

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

Contributor guide

Tech stack
javascriptnodejs
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Node.jsnode canvas basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
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.