A deterministic text layout and rendering engine for Go. This library provides consistent, cross-platform text wrapping, alignment, and spacing, with output support for ASCII, SVG, and bitmap (PNG) formats.

• Deterministic Layout: Produces identical output across all platforms
• Text Wrapping: Automatic word-wrapping to fit specified width
• Multiple Alignments: Left, center, right, and justify alignment
• Line Spacing: Configurable spacing between lines
• Tab Expansion: Consistent tab-to-space conversion
• Multiple Output Formats:
  • ASCII text with optional decorative borders
  • SVG (Scalable Vector Graphics)
  • PNG (bitmap images)
• CLI Tool: Command-line interface for easy text rendering
• Library API: Use as a Go library in your projects

go get github.com/BaseMax/go-text-render

go install github.com/BaseMax/go-text-render/cmd/go-text-render@latest

Or build from source:

git clone https://github.com/BaseMax/go-text-render.git
cd go-text-render
go build -o go-text-render ./cmd/go-text-render

# Basic usage with default settings (80 columns, left-aligned)
echo "Hello World" | go-text-render

# Center-aligned text with custom width
echo "Hello World" | go-text-render -width 40 -align center

# Add a decorative border
go-text-render -border -border-style double < input.txt

# Generate SVG output
go-text-render -format svg -width 60 input.txt -output output.svg

# Generate PNG image
go-text-render -format png -width 80 input.txt -output output.png

# Justify text with line spacing
go-text-render -align justify -spacing 1 -width 70 < input.txt

• -format: Output format (ascii, svg, or png) - default: ascii
• -width: Maximum text width in characters - default: 80
• -align: Text alignment (left, center, right, or justify) - default: left
• -spacing: Extra lines between text lines - default: 0
• -tab: Tab width in spaces - default: 4
• -border: Add border (ASCII format only) - default: false
• -border-style: Border style (single, double, or ascii) - default: single
• -output: Output file (default: stdout)
• -help: Show help message

package main

import (
    "fmt"
    "github.com/BaseMax/go-text-render"
)

func main() {
    text := "This is a long line of text that will be wrapped to fit within the specified width."
    
    options := textrender.LayoutOptions{
        Width:       40,
        Alignment:   textrender.AlignLeft,
        LineSpacing: 0,
        TabWidth:    4,
    }
    
    layout := textrender.Layout(text, options)
    fmt.Println(layout.String())
}

renderer := &textrender.ASCIIRenderer{
    Border:      true,
    BorderStyle: "double",
}

layout := textrender.Layout(text, options)
output := renderer.Render(layout)
fmt.Println(output)

options := textrender.LayoutOptions{
    Width:     60,
    Alignment: textrender.AlignCenter,
}

svgOutput := textrender.RenderSVG(text, options)
os.WriteFile("output.svg", []byte(svgOutput), 0644)

layout := textrender.Layout(text, options)
renderer := textrender.DefaultBitmapRenderer()

file, _ := os.Create("output.png")
defer file.Close()

renderer.RenderToPNG(layout, file)

renderer := &textrender.SVGRenderer{
    FontFamily: "Arial",
    FontSize:   16,
    LineHeight: 1.5,
    Padding:    20,
    Background: "#f0f0f0",
    TextColor:  "#333333",
}

layout := textrender.Layout(text, options)
svgOutput := renderer.Render(layout)

Text alignment options:

• AlignLeft - Left-aligned text
• AlignCenter - Center-aligned text
• AlignRight - Right-aligned text
• AlignJustify - Justified text (evenly distributed)

Configuration for text layout:

type LayoutOptions struct {
    Width       int       // Maximum width in characters
    Alignment   Alignment // Text alignment
    LineSpacing int       // Extra lines between text lines (0 = single spacing)
    TabWidth    int       // Number of spaces for tab character (default: 4)
}

• Layout(text string, options LayoutOptions) *TextLayout - Create a text layout
• DefaultLayoutOptions() LayoutOptions - Get default layout options
• RenderASCII(text string, options LayoutOptions, border bool, borderStyle string) string - Quick ASCII rendering
• RenderSVG(text string, options LayoutOptions) string - Quick SVG rendering
• RenderBitmap(text string, options LayoutOptions) image.Image - Quick bitmap rendering

See the examples directory for complete examples:

cd examples/basic
go run main.go

• Document Engines: Generate consistent text layouts for PDF or document generation
• Visual Diff Testing: Compare text layouts across different versions or platforms
• ASCII Art: Create bordered text boxes and formatted output
• Report Generation: Format text reports with proper alignment and spacing
• Web Graphics: Generate SVG text for web applications
• Image Generation: Create text-based images programmatically

This library is designed to produce identical output across all platforms by:

• Using consistent algorithms for text wrapping and alignment
• Avoiding platform-specific font rendering (for ASCII output)
• Using fixed-width calculations for layout
• Normalizing line endings and whitespace handling
• Providing explicit tab expansion

Run the test suite:

go test -v ./...

Run benchmarks:

go test -bench=. ./...

MIT License - see LICENSE file for details.

Contributions are welcome! Please feel free to submit a Pull Request.

BaseMax