Update README.md: Add CLI usage examples and new features

Author: ciwga

README.md

@@ -2,7 +2,7 @@
 <p align="center">
     <img src="assets/pdftoolkit.png" alt="PDF Toolkit" width="142"/>
 </p>
-PDF Toolkit is a Python application that provides a graphical user interface (GUI) for performing various operations on PDF files, such as editing metadata, extracting pages, and extracting images. The application is built using `tkinter` for the GUI and `PyPDF2` for PDF operations.
+PDF Toolkit is a Python application that provides both a graphical user interface (GUI) and a command-line interface (CLI) for performing various operations on PDF files. These operations include editing metadata, extracting pages and images, merging PDFs, and creating PDFs from images.
 
 ## Features
 
@@ -11,31 +11,86 @@ PDF Toolkit is a Python application that provides a graphical user interface (GU
 - **Save and Load Metadata**: Save metadata to a JSON file and load metadata from a JSON file.
 - **Page Operations**: Extract specific pages from a PDF file and save them as a new PDF.
 - **Image Operations**: Extract images from a PDF file and save them to a specified directory.
+- **PDF Merging**: Combine multiple PDF files into a single document.
+- **Image to PDF Conversion**: Convert image files to PDF with customizable page settings.
 - **Drag and Drop**: Drag and drop PDF files directly into the application for easy loading.
 - **Window Centering**: The application window opens centered on the screen.
+- **CLI Interface**: Use all features via command-line for batch operations.
 
 ## Requirements
 
 - Python 3.7+
 - `PyPDF2` library
 - `tkinterdnd2` library
+- `pillow` library
 
 You can install the required library using the following command:
 
-```sh
+```
 pip install -r requirements.txt
 ```
 
 ## Usage
-**Running the Application**
+### **Running the Application (GUI)**
 
-To run the application, execute the following command:
-```bash
+To launch the graphical user interface, execute the following command:
+```
 python pdftoolkit.py
 ```
 
-### User Interface
+### **Command-Line Interface (CLI)**
+
+The PDF Toolkit CLI supports various operations on PDF files. Below are some usage examples:
+#### Read PDF Metadata
+```
+pdftoolkit_cli.py read example.pdf
+```
+This command reads the metadata of the specified PDF file.
+#### Validate a PDF File
+```
+pdftoolkit_cli.py validate example.pdf
+```
+This command checks whether the provided PDF file is valid.
+#### Extract Specific Pages
+```
+pdftoolkit_cli.py extract-pages example.pdf "1-3,5" extracted.pdf
+```
+Extracts pages 1-3 and page 5 from the PDF and saves them to a new file.
+#### Merge Multiple PDFs
+```
+pdftoolkit_cli.py merge file1.pdf file2.pdf merged.pdf
+```
+Merges the listed PDF files into a single PDF.
+#### Create a PDF from Images
+You can specify margins either individually or as a sequence of four values.
+
+**Using Individual Margin Arguments:**
+```
+pdftoolkit_cli.py create-from-images img1.jpg img2.png output.pdf \
+    --margin-left 0 --margin-right 0 --margin-top 0 --margin-bottom 0 \
+    --page-size A4 --orientation portrait --scaling "scale to fit"
+```
+
+**Using Sequential Margin Values:**
+```
+pdftoolkit_cli.py create-from-images img1.jpg img2.png output.pdf \
+    --margins 0 0 0 0 --page-size A4 --orientation portrait --scaling 1
+```
+Default margin values (left, right, top, bottom) are 10.
+
+The ```--scaling``` option accepts both text values (e.g., "scale to fit", "stretch to fit", "actual size", "stretch to fill") and integer values (1-4) mapping to these options.
+
+
+## User Interface
 
 The following image shows the graphical user interface of the PDF Toolkit:
 
-![PDF Toolkit GUI](assets/gui.png)
+<div align="center">
+  <table>
+    <tr>
+      <td><img src="assets/gui.png" width="900" alt="PDF Operations Tab"></td>
+      <td><img src="assets/gui_merger_tab.png" width="900" alt=" PDF Merger Tab"></td>
+      <td><img src="assets/gui_image_to_pdf_tab.png" width="900" alt="Image to PDF Tab"></td>
+    </tr>
+  </table>
+</div>