img

img

Functions for optimizing, resizing, and converting images using libvips.

Table of Contents

• Features
• Prerequisites
• Installation
• Usage
• Supported Formats
• Performance Notes
• Sponsorship
• License

Features

• Parallel processing for batch operations
• Automatic format detection based on file content
• Preserves original if optimization does not reduce file size
• Stripped metadata
• Compress images with format-specific settings tuned for web

Prerequisites

• Go 1.25 or later
• libvips

Arch Linux:

sudo pacman -S libvips

macOS:

brew install vips

Ubuntu/Debian:

sudo apt install libvips-dev

See libvips install instructions for other platforms.

Installation

go get github.com/andmitr/pkg/img

Usage

func Optimize

func Optimize(file string, outDir string) error

Optimize compresses a single image and saves it as filename_min.ext in outDir.

Parameters:

• file - path to input image
• outDir - directory for output file

Returns error if file cannot be read or processed.

Example

err := img.Optimize("inputDir/photo.jpg", "outputDir")
// Creates: outputDir/photo_min.jpg

The function applies format-specific compression:

• JPEG: quality 70, interlaced
• PNG: compression 6, palette mode, quality 85
• WebP: quality 80
• AVIF: quality 70, speed 7
• SVG: minified via tdewolff/minify

Note
Compression options are hardcoded for optimal web performance. If you need custom settings, fork the repository and modify the options in optimize.go.

func OptimizeAll

func OptimizeAll(inDir string, outDir string) error

OptimizeAll processes all supported images in inDir and saves optimized versions to outDir.

Processes files in parallel using all available CPU cores. Skips files with unsupported extensions.

Example

err := img.OptimizeAll("inputDir", "outputDir")
// Processes all supported images in parallel
// Creates: outputDir/photo1_min.jpg, outputDir/photo2_min.png, etc.

func Resize

func Resize(file string, outDir string, width int, height int) error

Resize creates a new image stretched to the specified dimensions.

Parameters:

• file - path to input image
• outDir - directory for output file
• width - target width in pixels
• height - target height in pixels

Example

err := img.Resize("input/photo.jpg", "output", 800, 600)
// Creates: output/photo_800x600.jpg
// Stretches the image to exactly 800x600 pixels.

func Convert

func Convert(file string, outDir string, outType string) error

Convert transforms an image to a different format.

Parameters:

• file - path to input image
• outDir - directory for output file
• outType - target format: jpg, jpeg, png, webp, avif

Example

err := img.Convert("input/photo.png", "output", "webp")
// Creates: output/photo.webp

Supported Formats

Performance Notes

• OptimizeAll uses goroutine pooling with a limit of runtime.NumCPU() to prevent excessive memory usage
• Processing order is non-deterministic due to parallel execution
• AVIF encoding is slower but provides excellent compression
• SVG optimization uses a different pipeline (minify) rather than libvips

Sponsorship

1CCnwAvJYEoDVGM7vsBg2Q99cF9EHtBVaY

0x54f0ccc6b2987de454f69f2814fc9202bcfb74fe

License

MIT Licensed. See LICENSE for details.