How to have Imagemagick make use of Ghostscript

[chamby]

Additional Info

• I am using Windows Subsystem for Linux

Output of brew config

HOMEBREW_VERSION: 4.6.4
ORIGIN: https://github.com/Homebrew/brew
HEAD: 160af073a53fcb23331d70d79785d17d13da41e7
Last commit: 4 days ago
Branch: stable
Core tap JSON: 21 Aug 14:28 UTC
HOMEBREW_PREFIX: /home/linuxbrew/.linuxbrew
HOMEBREW_CASK_OPTS: []
HOMEBREW_FORBID_PACKAGES_FROM_PATHS: set
HOMEBREW_MAKE_JOBS: 32
Homebrew Ruby: 3.4.5 => /home/linuxbrew/.linuxbrew/Homebrew/Library/Homebrew/vendor/portable-ruby/3.4.5/bin/ruby
CPU: 32-core 64-bit zen3
Clang: N/A
Git: 2.34.1 => /bin/git
Curl: 7.81.0 => /bin/curl
Kernel: Linux 5.15.0-144-generic x86_64 GNU/Linux
OS: Ubuntu 22.04.3 LTS (jammy)
Host glibc: 2.35
/usr/bin/gcc: 11.4.0
/usr/bin/ruby: N/A
glibc: N/A
gcc@11: N/A
gcc: N/A
xorg: N/A

Output of brew doctor

Your system is ready to brew.

Description of issue

Running magick --version reports:

Version: ImageMagick 7.1.2-1 Q16-HDRI aarch64 23308 https://imagemagick.org
Copyright: (C) 1999 ImageMagick Studio LLC
License: https://imagemagick.org/script/license.php
Features: Cipher DPC HDRI Modules OpenMP(4.5) 
Delegates (built-in): bzlib fontconfig freetype heic jng jp2 jpeg jxl lcms lqr ltdl lzma openexr png raw tiff webp x xml zlib zstd
Compiler: gcc (11.4)

The installation of Imagemagick reports the following:

==> Caveats
Ghostscript is not installed by default as a dependency.
If you need PS or PDF support, ImageMagick will still use the ghostscript formula if installed directly.

My interpretation of that statement is that installing Ghostscript via Homebrew will allow Imagemagick to dynamically link to the Ghostscript library. I did install Ghostscript via Homebrew as well. Apparently, more is required, but I am not sure how to proceed.

The core formula is built without gslib by default.

https://github.com/Homebrew/homebrew-core/blob/6b4b884f8b777c20027d223c4edc7a69b2dbe18d/Formula/i/imagemagick.rb#L80

#4308 indicates that:

Options were removed from Homebrew/core 5 years ago. If you need modifications to a formula you need to maintain your own tap.

Does this mean I should edit the formula and built with --with-gslib instead, or is there a simpler way to have Imagemagick make use of Ghostscript dynamically?

[carlocab]

Per Homebrew/homebrew-core#220197, you don't need imagemagick to link dynamically with ghostscript in order to use imagemagick with ghostscript. You just need to have ghostscript installed. But CC @Bo98 in case there are additional caveats here.

What are you trying to do, exactly?

[Bo98]

Without gslib (i.e. no MAGICKCORE_GS_DELEGATE), it should just execute gs via command line: https://github.com/ImageMagick/ImageMagick/blob/d0db80477e14ee04cc73a006a78ab6892b07a369/coders/ghostscript-private.h#L200, https://github.com/ImageMagick/ImageMagick/blob/d0db80477e14ee04cc73a006a78ab6892b07a369/MagickCore/delegate.c#L120-L121 (see also: https://www.imagemagick.org/discourse-server/viewtopic.php?p=86404&sid=3ba465f8932a6e6ae4278d805a2b00c8#p86404).

Not being reported by --version is intentional. The delegate list is not a list of supported formats.

[Bo98]

One thing maybe to check is if the PATH is getting passed through correctly. If not, we could update the delegate map (https://github.com/ImageMagick/ImageMagick/blob/d0db80477e14ee04cc73a006a78ab6892b07a369/config/delegates.xml.in, https://github.com/ImageMagick/ImageMagick/blob/d0db80477e14ee04cc73a006a78ab6892b07a369/configure.ac#L3366) to use absolute paths.

[chamby]

This is not a Homebrew issue. I apologize for not describing my use case. It was an oversight.

I was attempting the simple command

identify -format '%m' test.ai
identify: attempt to perform an operation not allowed by the security policy `PDF' @ error/module.c/OpenModule/1268.
identify: no decode delegate for this image format `PDF' @ error/constitute.c/ReadImage/746.

My policy.xml file was configured as follows to allow read access

<policy domain="delegate" rights="none" pattern="*" />
<policy domain="module" rights="read" pattern="{PS,PS2,PS3,EPS,PDF,XPS}"/>

which I thought would be sufficient. When I change the policy to allow read+write access

<-- <policy domain="delegate" rights="none" pattern="*" /> -->
<policy domain="module" rights="read | write" pattern="{PS,PS2,PS3,EPS,PDF,XPS}"/>
                                       ^^^^^

I can decode the file format.

If I leave the delegate rights restriction in place the error is slightly different.

identify: attempt to perform an operation not allowed by the security policy `gs' @ error/delegate.c/ExternalDelegateCommand/396.

I do not know the correct way to fix the gs security policy restriction without removing it entirely from the policy. I'd prefer to have a more secure deployment and whitelist the delegate, but I can't figure out the correct configuration.