Troubleshooting "Convert: Not Authorized" Error When Converting JPG to PDF in Ubuntu

Encountering errors while trying to convert JPG files to PDF on Ubuntu can be frustrating. One common issue is the "convert: not authorized pictures.pdf'" error, which arises when using the convert` command from ImageMagick. This article provides a detailed explanation of the cause and offers several solutions to resolve it.

Understanding the "Not Authorized" Error

The error message "convert: not authorized `pictures.pdf' @ error/constitute.c/WriteImage/1028" indicates a permission issue within ImageMagick's security policy. A security update in ImageMagick, specifically version 8:6.8.9.9-7ubuntu5.13, introduced restrictions on certain operations, including PDF conversion, to mitigate potential vulnerabilities. This update modified the default policy to restrict the reading and writing of PDF files, hence the "not authorized" error.

Solutions to Fix the Conversion Error

Here are several approaches to resolve the "convert: not authorized" error:

1. Modifying the ImageMagick Policy File (Temporary Fix)

Warning: While this is a quick fix reported by several users, modifying security settings can expose your system to risks. Proceed with caution.

1. Locate the policy.xml file: The file is typically located in /etc/ImageMagick-6/policy.xml.

2. Edit the file: Open the file with root privileges using a text editor like nano or vim.

   sudo nano /etc/ImageMagick-6/policy.xml
   

3. Change PDF rights: Find the line that restricts PDF rights. It usually looks like this:

   <policy domain="coder" rights="none" pattern="PDF" />
   

   Change rights="none" to rights="read|write":

   <policy domain="coder" rights="read|write" pattern="PDF" />
   

   Alternatively, you can comment out or remove the entire line.

   Note: Some users have stated " Change destination file format policy respectively .Usually they will be at the end .Thanks"

4. Save the file: Save the changes and exit the text editor.

This allows ImageMagick to read and write PDF files, resolving the error.

Automated Fix (using sed)

A one-liner using sed can automate the process:

sudo sed -i 's#<policy domain="coder" rights="none" pattern="PDF" />#<policy domain="coder" rights="read|write" pattern="PDF" />#' /etc/ImageMagick-6/policy.xml

2. Using img2pdf (Recommended Solution)

A safer and more recommended method is to use the img2pdf tool, which is specifically designed for converting images to PDF without relying on potentially insecure ImageMagick configurations.

1. Install img2pdf: If it's not already installed, install it using apt:

   sudo apt install img2pdf
   

2. Convert JPG to PDF: Use the following command:

   img2pdf --output out.pdf in.jpg
   

   Replace in.jpg with the name of your JPG file and out.pdf with the desired name for the output PDF file. You can also convert multiple JPG files at once:

   img2pdf image1.jpg image2.jpg -o output.pdf
   

img2pdf is considered safer because it doesn't require disabling security limitations within ImageMagick, respecting the intended security measures.

3. Using pdftoppm and ImageMagick

Another alternative involves using pdftoppm (from the poppler-utils package) to convert the PDF to a series of JPEG images, then use Imagemagick or another tool to convert those back to a PDF. This sounds counter-intuitive for converting JPG to PDF, but if you are having issues converting PDF to JPG, this is a valid solution.

1. Install poppler-utils:

   sudo apt-get install poppler-utils
   

2. Convert PDF to JPEG:

   pdftoppm -jpeg input.pdf output
   

   This will create output-01.jpg, output-02.jpg, etc., for each page of the PDF.

4. Considering Ghostscript Updates

If security implications are a concern, ensure Ghostscript is up to date. The Ghostscript Release Notes mention fixes to vulnerabilities. Updating ghostscript may resolve the underlying issue preventing ImageMagick from functioning correctly.

Choosing the Right Solution

• For a quick but potentially less secure fix, modifying the policy.xml file might suffice. Remember to revert after conversion if security is paramount.
• For a safer, more controlled approach, img2pdf is the preferred method.
• If the initial issue was converting PDF to JPG use pdftoppm

Always prioritize security when making system changes. Consider the implications before disabling security features. It's often best to utilize alternative tools designed to work within existing security constraints.