PlantUML ASCII Art Diagram Generator

Overview

Create text-based ASCII art diagrams using PlantUML. Perfect for documentation in terminal environments, README files, emails, or any scenario where graphical diagrams aren't suitable.

What is PlantUML ASCII Art?

PlantUML can generate diagrams as plain text (ASCII art) instead of images. This is useful for:

Terminal-based workflows
Git commits/PRs without image support
Documentation that needs to be version-controlled
Environments where graphical tools aren't available

Installation

# macOS
brew install plantuml

# Linux (varies by distro)
sudo apt-get install plantuml  # Ubuntu/Debian
sudo yum install plantuml      # RHEL/CentOS

# Or download JAR directly
wget https://github.com/plantuml/plantuml/releases/download/v1.2024.0/plantuml-1.2024.0.jar

Output Formats

Flag	Format	Description
`-txt`	ASCII	Pure ASCII characters
`-utxt`	Unicode ASCII	Enhanced with box-drawing characters

Basic Workflow

1. Create PlantUML Diagram File

@startuml
participant Bob
actor Alice

Bob -> Alice : hello
Alice -> Bob : Is it ok?
@enduml

2. Generate ASCII Art

# Standard ASCII output
plantuml -txt diagram.puml

# Unicode-enhanced output (better looking)
plantuml -utxt diagram.puml

# Using JAR directly
java -jar plantuml.jar -txt diagram.puml
java -jar plantuml.jar -utxt diagram.puml

3. View Output

Output is saved as diagram.atxt (ASCII) or diagram.utxt (Unicode).

Diagram Types Supported

Sequence Diagram

@startuml
actor User
participant "Web App" as App
database "Database" as DB

User -> App : Login Request
App -> DB : Validate Credentials
DB --> App : User Data
App --> User : Auth Token
@enduml

Class Diagram

@startuml
class User {
  +id: int
  +name: string
  +email: string
  +login(): bool
}

class Order {
  +id: int
  +total: float
  +items: List
  +calculateTotal(): float
}

User "1" -- "*" Order : places
@enduml

Activity Diagram

@startuml
start
:Initialize;
if (Is Valid?) then (yes)
  :Process Data;
  :Save Result;
else (no)
  :Log Error;
  stop
endif
:Complete;
stop
@enduml

State Diagram

@startuml
[*] --> Idle
Idle --> Processing : start
Processing --> Success : complete
Processing --> Error : fail
Success --> [*]
Error --> Idle : retry
@enduml

Component Diagram

@startuml
[Client] as client
[API Gateway] as gateway
[Service A] as svcA
[Service B] as svcB
[Database] as db

client --> gateway
gateway --> svcA
gateway --> svcB
svcA --> db
svcB --> db
@enduml

Use Case Diagram

@startuml
actor "User" as user
actor "Admin" as admin

rectangle "System" {
  user -- (Login)
  user -- (View Profile)
  user -- (Update Settings)
  admin -- (Manage Users)
  admin -- (Configure System)
}
@enduml

Deployment Diagram

@startuml
actor "User" as user
node "Load Balancer" as lb
node "Web Server 1" as ws1
node "Web Server 2" as ws2
database "Primary DB" as db1
database "Replica DB" as db2

user --> lb
lb --> ws1
lb --> ws2
ws1 --> db1
ws2 --> db1
db1 --> db2 : replicate
@enduml

Command-Line Options

# Specify output directory
plantuml -txt -o ./output diagram.puml

# Process all files in directory
plantuml -txt ./diagrams/

# Include dot files (hidden files)
plantuml -txt -includeDot diagrams/

# Verbose output
plantuml -txt -v diagram.puml

# Specify charset
plantuml -txt -charset UTF-8 diagram.puml

Ant Task Integration

<target name="generate-ascii">
  <plantuml dir="./src" format="txt" />
</target>

<target name="generate-unicode-ascii">
  <plantuml dir="./src" format="utxt" />
</target>

Tips for Better ASCII Diagrams

Keep it simple: Complex diagrams don't render well in ASCII
Short labels: Long text breaks ASCII alignment
Use Unicode (-utxt): Better visual quality with box-drawing chars
Test before sharing: Verify in terminal with fixed-width font
Consider alternatives: For complex diagrams, use Mermaid.js or graphviz

Example Output Comparison

Standard ASCII (-txt):

     ,---.          ,---.
     |Bob|          |Alice|
     `---'          `---'
      |   hello      |
      |------------->|
      |              |
      |  Is it ok?   |
      |<-------------|
      |              |

Unicode ASCII (-utxt):

┌─────┐        ┌─────┐
│ Bob │        │Alice│
└─────┘        └─────┘
  │   hello      │
  │─────────────>│
  │              │
  │  Is it ok?   │
  │<─────────────│
  │              │

Quick Reference

# Create sequence diagram in ASCII
cat > seq.puml << 'EOF'
@startuml
Alice -> Bob: Request
Bob --> Alice: Response
@enduml
EOF

plantuml -txt seq.puml
cat seq.atxt

# Create with Unicode
plantuml -utxt seq.puml
cat seq.utxt

Troubleshooting

Problem: Garbled Unicode characters

Solution: Ensure terminal supports UTF-8 and has proper font

Problem: Diagram looks misaligned

Solution: Use fixed-width font (Courier, Monaco, Consolas)

Problem: Command not found

Solution: Install PlantUML or use Java JAR directly

Problem: Output file not created

Solution: Check file permissions, ensure PlantUML has write access

plantuml-ascii

Preview