Update README.md describing currently available functionality

README.md

@@ -1,24 +1,43 @@
 # Fotos
 
-TODO: Delete this and the text below, and describe your gem
-
-Welcome to your new gem! In this directory, you'll find the files you need to be able to package up your Ruby library into a gem. Put your Ruby code in the file `lib/fotos`. To experiment with that code, run `bin/console` for an interactive prompt.
+A Ruby gem for creating static HTML photo galleries from organized image directories. Fotos extracts EXIF data, generates thumbnails, and creates date-organized HTML galleries.
 
 ## Installation
 
-TODO: Replace `UPDATE_WITH_YOUR_GEM_NAME_IMMEDIATELY_AFTER_RELEASE_TO_RUBYGEMS_ORG` with your gem name right after releasing it to RubyGems.org. Please do not do it earlier due to security reasons. Alternatively, replace this section with instructions to install your gem from git if you don't plan to release to RubyGems.org.
+Install the gem locally:
 
-Install the gem and add to the application's Gemfile by executing:
+    $ bundle exec rake install
 
-    $ bundle add UPDATE_WITH_YOUR_GEM_NAME_IMMEDIATELY_AFTER_RELEASE_TO_RUBYGEMS_ORG
+    gem 'fotos', git: 'https://src.niebo.net/lukasz/fotos.git'
 
-If bundler is not being used to manage dependencies, install the gem by executing:
+## Usage
 
-    $ gem install UPDATE_WITH_YOUR_GEM_NAME_IMMEDIATELY_AFTER_RELEASE_TO_RUBYGEMS_ORG
+Fotos provides three main commands for processing images:
 
-## Usage
+### Extract Images from ZIP Files
+
+    $ fotos extract -z PATH_TO_ZIP [-d DESTINATION]
+
+Extracts images from a ZIP archive to a destination directory (defaults to current directory).
+
+### Organize Images by Date
+
+    $ fotos organize -s SOURCE_DIR -d DESTINATION_DIR
+
+Reads EXIF data from images and organizes them into date-named directories (DD-MM-YYYY format). Only supports JPEG/JPG files currently.
+
+### Generate HTML Gallery
+
+    $ fotos build -s SOURCE_DIR [-d OUTPUT_DIR] [-t]
+
+Creates an HTML photo gallery from organized image directories:
+- `-s` specifies the source directory containing date-organized subdirectories
+- `-d` specifies the output directory (defaults to current directory)
+- `-t` automatically generates missing thumbnails
 
-TODO: Write usage instructions here
+The gallery includes:
+- Date-based organization with Polish month names
+- Thumbnail navigation
 
 ## Development