PlantUML Image Generator

When to Apply

• When the user asks "draw a diagram for me" or "I need an architecture/flowchart/sequence/state-machine diagram".
• When the user requires inserting an illustration of business processes or structural diagrams into development documents, READMEs, or any Markdown files.
• When you need to visually explain complex code logic to the user for better understanding.

Execution Rules

1. Requirement Analysis & Code Generation:

   • Extract the elements and relationships that need visualization based on the user's context.
   • Write standard PlantUML syntax code (must start with @startuml and end with @enduml).

2. Core Encoding Logic (URL Generation): Convert the generated PlantUML code into ENCODED_TEXT using specific encoding rules:

   • First, encode the PlantUML source code into UTF-8.
   • Compress it using the zlib / Deflate algorithm.
   • Re-encode the compressed result using PlantUML's specialized Base64 dictionary (variant: 0-9, A-Z, a-z, -, _).

3. URL Assembly: Append the generated ENCODED_TEXT to the official main service URL, supporting two mainstream formats:

   • PNG Raster Image: http://www.plantuml.com/plantuml/png/{ENCODED_TEXT}
   • SVG Vector Image (Recommended, scales without distortion): http://www.plantuml.com/plantuml/svg/{ENCODED_TEXT}

4. Rendering & Insertion:

   • Wrap the assembled URL using standard Markdown image syntax: ![Image Description/Alt](URL)
   • Reply directly to the user with this Markdown line, or use file editing tools to insert it into the appropriate location in the document.

Code Reference (Auto-Helper Script / Python Example)

If you need to write a script to quickly verify the encoding process, refer to the following conversion logic:

import zlib
import base64

def generate_plantuml_url(uml_text: str, output_format: str = "svg") -> str:
    utf8_data = uml_text.encode('utf-8')
    compressor = zlib.compressobj(9, zlib.DEFLATED, -zlib.MAX_WBITS)
    compressed_data = compressor.compress(utf8_data) + compressor.flush()
    b64_str = base64.b64encode(compressed_data)
    trans = bytes.maketrans(
        b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/",
        b"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-_"
    )
    encoded_str = b64_str.translate(trans).decode('utf-8').rstrip('=')
    return f"http://www.plantuml.com/plantuml/{output_format}/{encoded_str}"

Input/Output Example (Edge Cases & Examples)

Input Context: "Boss: Add a sequence diagram to the README explaining the user login process."

Internal Execution (PlantUML Source):

@startuml
User -> Server: Send username and password
Server -> Database: Validate credentials
Database --> Server: Return UserID and Token
Server --> User: Login successful
@enduml

Your Final Output (Written directly in the document or feedback message):

![User Login Sequence Diagram](http://www.plantuml.com/plantuml/svg/SoWkIImgAStDuKfCoKnELT2rKt3CJJ58I2nAp5K8I2rEBajCJbNmN4h5iKj2hG0uW55nWgIWHXyWDB4PqEIgvWhGgfE2Kz2rKt240000)