UNO image manipulation example

This repo contains example extension for LibreOffice. It shows how to use UNO and Python to extract and manipulate images in LibreOffice Writer document.

This plugin is self contained in that it contains the full source to build itself. To do so, unpack the oxt-extension with any program able to read the zip format. Running the script './build' in the unpacked source tree, will then recreate the extension (and possible modifications).

Running

How to run extension and how to change its behavior.

Current state

Extension adds a new button to LibreOffice toolbar, which looks like this: For now, when user press this button, extension will export all images from current document to /tmp folder. See file Addons.xcu for "URL" property (it sets argument to ImageExample service).

Changing behavior

Extension can send all images from current document to remote server, get them back, and replace them in document. If remote server does some processing of pixels (for example, makes them grayscale), it is possible to apply some effect to all images in document at once.

To enable this behavior user needs to change argument passed to ImageExample service (Addons.xcu: change "export_images" in "URL" property to "grayscale_images") and set remote server address and port (uno_image.py: look for "TODO", set IP address of a server and its port). After that, it is needed to build extension (run ./build) and install it to LibreOffice again.

Limitations

• Extension assumes it is run on UNIX system with /tmp path. It is easy to fix this limitation by changing code in generate_tmp_path().
• There is no any config to set server address and port to send images.
• Extension is dumb. It sends to server raw pixel values instead of original image, assuming that server will not change image size or format.

Files

Following below is a description of all the files in this extension and how LibreOffice learns what to do with them.

Extension entry points

• ./description.xml - This file (and those that it references) describes the extension, its license in a human readable form.
• ./META-INF/manifest.xml - This file explains the contents of the extension for LibreOffice to inject.

Files referenced from description.xml

• ./description/license.txt - License shown to the user on installation.
• ./description/description_en.txt - Human readable description to show e.g. in the extension manager.
• ./description/extensionicon.png - Icon to show e.g. in the extension manager
• ./description/icon.xcf - Icon source image from GIMP

Files referenced from manifest.xml

• ./uno_image.py - Python script that implements a service called org.libreoffice.imageexample.ImageExample
• ./Addons.xcu - Describes how this extension wants to modify the toolbar. It adds an icon "Grayscale images" that triggers the org.libreoffice.imageexample.ImageExample service with "export_images" argument.
• ./images/ - Images in this folder used by Addons.xcu to add icon to new button.

Files not referenced anywhere and ignored at runtime

• ./build - A simple python script that packs the extension from the unpacked source.
• ./extensionname.txt - A file hinting ./build how to name the produced .oxt file.
• ./README.md - This file.
• ./test_server.py - Example server for extension. It fills all received pixels with \x00 value and sends them back.