Tricks

To capture the rendered image from the virtual display (since the program itself doesn't save it), you can use a screen capture tool that works with virtual displays like Xvfb. Here's how you can achieve this:

Steps to Capture the Image from the Virtual Display

1. Install xwd (X Window Dump):

   • xwd is a utility that captures the contents of an X Window display (including virtual displays created by Xvfb).
   • Install x11-apps package, which includes xwd:

     sudo apt-get install x11-apps   # Debian/Ubuntu-based systems
     sudo yum install xorg-x11-apps  # RHEL/CentOS-based systems
     

2. Run Your Program with Xvfb:
   After setting up Xvfb as mentioned before, run the program in the virtual display:

   Xvfb :99 -screen 0 1024x768x24 &
   export DISPLAY=:99
   ./your_program
   

3. Capture the Screen Using xwd:
   Use xwd to capture the contents of the virtual display as an image:

   xwd -root -display :99 -out screenshot.xwd
   

   This will capture the entire virtual display and save it as a file named screenshot.xwd.

4. Convert the Captured Image (Optional):
   The output format (.xwd) might not be suitable for direct use. You can convert it to a more common format (like PNG or JPEG) using tools such as ImageMagick:

   • Install ImageMagick:

     sudo apt-get install imagemagick
     

   • Convert .xwd to .png:

     convert screenshot.xwd screenshot.png
     

5. View the Image:

   • Once the image is converted to a more common format like PNG, you can transfer the file back to your Mac and view it using any standard image viewer.
   • To transfer the file:

     scp user@yourserver.com:/path/to/screenshot.png /local/path/
     

Full Process Example:

# Start Xvfb
Xvfb :99 -screen 0 1024x768x24 &
export DISPLAY=:99

# Run your program
./your_program &

# Capture the virtual display
xwd -root -display :99 -out screenshot.xwd

# Convert to PNG format
convert screenshot.xwd screenshot.png

# (Optional) Transfer to local Mac
scp user@yourserver.com:/path/to/screenshot.png /local/path/

This process allows you to render the image in the virtual display, capture it, and then convert and view it locally.

Would this workflow work for you?