OpenImg Go

A Go image processing service that provides image transformation, metadata retrieval, and placeholder generation with caching support.

Features

• Image Transformation
  • Resize with width/height parameters
  • Format conversion (JPEG, PNG, AVIF, WebP)
  • High-quality AVIF compression
  • Quality control for lossy formats
  • Multiple fit modes (cover, contain)
• Image Metadata
  • Dimensions (width, height)
  • Format detection
  • MIME type
• Placeholder Generation
  • Base64 encoded low-quality previews
  • Configurable dimensions and quality
• Performance
  • In-memory caching
  • Efficient metadata extraction
  • Optimized image processing

Getting Started

Prerequisites

Install Go (1.21 or later)

System dependencies:

• macOS:

  brew install aom  # Required for AVIF support

• Ubuntu/Debian:

  sudo apt-get install libaom-dev  # Required for AVIF support

Installation

1. Clone the repository

   git clone https://github.com/deyshin/openimg-go
   cd openimg-go

2. Install dependencies

   go mod download

3. Install Air for hot reloading (optional)

   go install github.com/cosmtrek/air@latest

Running the Server

Run with hot reloading:

air

Or run normally:

go run main.go

API Endpoints

Images

GET /api/image?url=<image_url>&w=<width>&h=<height>&fmt=<format>&q=<quality>&fit=<fit>
http://localhost:8080/api/image?url=https://example.com/image.jpg&w=800&h=600&fmt=jpeg&q=80&fit=cover

Metadata

GET /api/image?url=<image_url>&metadata=true

Example Response:

{
"width": 800,
"height": 600,
"format": "jpeg",
"mimeType": "image/jpeg"
}

Placeholder

GET /api/image?url=<image_url>&placeholder=true&w=<width>&h=<height>&q=<quality>

Structure

.
├── main.go # Server and handler implementation
├── internal/
│ ├── cache/ # Caching implementation
│ ├── devserver/ # Development server utilities
│ ├── metadata/ # Image metadata handling
│ ├── transform/ # Image transformation logic
│ ├── validate/ # Input validation
│ └── testdata/ # Test files and examples
└── .air.toml # Air configuration for hot reloading

Running Tests

# Run all tests
CGO_CFLAGS="-Wno-xor-used-as-pow" go test -v ./...
# Run tests for specific package
CGO_CFLAGS="-Wno-xor-used-as-pow" go test -v ./internal/transform
go test -v ./internal/metadata
go test -v ./internal/validate
go test -v ./internal/cache

Running the Server

GO_ENV=development go run main.go