imagemin — WebP Image Processing for SSR Modules

imagemin discovers images declared in ssr.go files of Go modules, converts them to WebP with responsive variants (L, M, S), and writes them to web/public/img/.

Features

• Responsive Variants: Automatically generates S (640px), M (1024px), and L (1920px) variants.
• WebP Optimized: Uses WebP for superior compression and quality.
• Stat-based Caching: Uses file modification times (mtime) to avoid redundant processing without extra state files.
• No Upscaling: Never enlarges images smaller than the target variant size.
• AST-based Extraction: Discovers images by parsing source code, no runtime execution required.

Documentation

For a detailed look at the internal workings and design decisions, see the Architecture Documentation.

Usage in ssr.go

Modules declare their images by implementing a RenderImages function:

//go:build !wasm

package mymodule

import "github.com/tinywasm/imagemin"

func RenderImages() []imagemin.Asset {
    return []imagemin.Asset{
        {
            Path: "img/logo.png",
            Variants: imagemin.VariantS | imagemin.VariantM,
            Alt: "Company Logo",
        },
        {
            Path: "img/hero.jpg",
            Variants: imagemin.AllVariants,
        },
    }
}

Architecture Overview

• types.go: Core types (Asset, Variant) shared across all contexts.
• extract.go: AST parser that finds RenderImages declarations in modules.
• convert.go: Image processing logic using imaging and nativewebp.
• loader.go: Module discovery and orchestration using go list.
• imagemin.go: Main Handler that implements the devwatch interfaces.

API

Configuration

type Config struct {
    RootDir   string // Project root (where go.mod is)
    OutputDir string // Output directory for WebP images (e.g., "web/public/img")
    Quality   int    // WebP quality (0-100)
}

Handler

handler := imagemin.New(&config)
handler.InitDefaultLoader() // Uses 'go list' for discovery
err := handler.LoadImages() // Initial load