Command Line Tool which is included in Astah installation folder enables you to export images and compare projects from Command-Line.

Export image files

By using -image option with astah-commandw.exe (for Windows) or astah-command.sh (For Mac or Linux),
you can export diagram images as PNG, JPEG, EMF or SVG.
If you do not specify the image format, it exports in PNG format automatically.

[Windows] Export all the diagrams in the C:\input\hoge.asta.file to C:\output in PNG

astah-commandw.exe -image er -f C:\input\hoge.asta -o C:\output

[Mac/Linux] Export all the diagrams in ~/input/hoge.asta file to ~/output in JPEG

astah-command.sh -image all -f ~/input/hoge.asta -o ~/output -t jpg