Install Alpha Manager plugin to CKEditor

After installing the add-on will be available from the standard "Image properties" dialog.

CKEditor AlphaManager screenshot
  1. Unpack archived files directly to ckeditor/plugins.
  2. Turn on the plugin in ckeditor/config.js:
    config.extraPlugins = 'alphamanager';
  3. Now you can use your installed plugins. Do not forget to sure that browser cache was cleared.