ImageMagick Mac/Linux 版本之间的行为不一致。 Linux 上的 CMYK 文件损坏

Question

I am bulk converting PDF's to TIFF images.

bash scripts are written on and tested on a Mac, then pushed to a Ubuntu box for production runs. (it has better spec)

Strangely, some pages (1 in 100 or so) exported images are corrupted. after multiple runs, image corruption happens on the same pages, suggesting this is not a random runtime error.

Pages are exported from Adobe InDesign CC2020 using the same PDF/X4 profile. All follows similar composition of text with styles, placed over monochrome images.

Left: Correct / Right: Corrupted

Just for completeness, I tried im6 (ubuntu20.4 default) convert command, but resulted with the same result.

This is the options I run my batch (via GNU Parallel). Is there something wrong I may be doing, in my script?

    convert \
        -verbose \
        -alpha off \
        -colorspace Gray \
        -contrast-stretch 0 \
        -depth 8 \
        -compress zip \
        -units PixelsPerInch \
        -density 1200  \
        ${1} \
        ${1%.*}.tiff

From searching I found that there may be issues between im6 and im7 and how they handle colour profiles, but they are version matched as below:

versions as shown by magick --version :

Mac (homebrew):
Version: ImageMagick 7.0.11-14 Q16 x86_64 2021-05-31 https://imagemagick.org
Copyright: (C) 1999-2021 ImageMagick Studio LLC
License: https://imagemagick.org/script/license.php
Features: Cipher DPC HDRI Modules OpenMP(5.0)
Delegates (built-in): bzlib fontconfig freetype gslib heic jng jp2 jpeg lcms lqr ltdl lzma openexr png ps tiff webp xml zlib

Ubuntu20.04 (v7 installed with https://github.com/SoftCreatR/imei/ )
Version: ImageMagick 7.0.11-14 Q32 x86_64 2021-05-17 https://imagemagick.org
Copyright: (C) 1999-2021 ImageMagick Studio LLC
License: https://imagemagick.org/script/license.php
Features: Cipher DPC HDRI Modules OpenMP(4.5)
Delegates (built-in): bzlib cairo djvu fftw fontconfig freetype gslib gvc heic jbig jng jp2 jpeg jxl lcms lqr ltdl lzma openexr pangocairo png ps raqm raw rsvg tiff webp wmf x xml zip zlib

And here are identify command result from PDF files:

identify result: PDF file with export problems

Image:
  Filename: 05.pdf
  Format: PDF (Portable Document Format)
  Mime type: application/pdf
  Class: DirectClass
  Geometry: 380x533+0+0
  Resolution: 72x72
  Print size: 5.27778x7.40278
  Units: Undefined
  Colorspace: CMYK
  Type: ColorSeparation
  Endianness: Undefined
  Depth: 16/8-bit
  Channel depth:
    Cyan: 1-bit
    Magenta: 1-bit
    Yellow: 1-bit
    Black: 8-bit

identify result: PDF file without problems:

Image:
  Filename: 06.pdf
  Format: PDF (Portable Document Format)
  Mime type: application/pdf
  Class: DirectClass
  Geometry: 380x533+0+0
  Resolution: 72x72
  Print size: 5.27778x7.40278
  Units: Undefined
  Colorspace: sRGB
  Type: PaletteAlpha
  Base type: Undefined
  Endianness: Undefined
  Depth: 16/8-bit
  Channel depth:
    Red: 8-bit
    Green: 8-bit
    Blue: 8-bit
    Alpha: 8-bit

I noticed that I seem to have problems with files in CMYK colourspace and not sRGB.

However, that to me does not explain why it works on a Mac, but not on Ubuntu.

Perhaps Ubuntu build, contain CMYK library different to Mac build? Is there a way to confirm my suspicion?

Answer 1

I may have arrived at a work around.

the issue seemed to arise from this part:

  Channel depth:
    Cyan: 1-bit
    Magenta: 1-bit
    Yellow: 1-bit
    Black: 8-bit

Original image is for print in monochrome. Such that all channels of CMY except K contains no data, stored as bit depth of 1.

Still not yet clear why it works on a Mac, but here's a version that works on Linux build too:

    convert \
        -verbose \
        -alpha off \
        -colorspace CMYK \
        -contrast-stretch 0 \
        -depth 8 \
        -channel black -negate -separate \
        -compress zip \
        -units PixelsPerInch \
        -density 1200  \
        ${1} \
        ${1%.*}.tiff

The key was to render in CMYK first, as original PDFs are intended for.

Then strip CMY channels, to create a pure Grayscale image. (note K channels need to be negated)

Snippet above works consistently for both Mac/Linux.