resize/README.md

Resize

Image resizing for the Go programming language that includes a few interpolation methods.

Installation

$ go get github.com/nfnt/resize

It's that easy!

Usage

Import package with

import "github.com/nfnt/resize"

Resize creates a scaled image with new dimensions (width, height) using the interpolation function interp. If either width or height is set to 0, it will be set to an aspect ratio preserving value.

resize.Resize(width, height uint, img image.Image, interp resize.InterpolationFunction) image.Image 

The provided interpolation functions are

• NearestNeighbor: Nearest-neighbor interpolation
• Bilinear: Bilinear interpolation
• Bicubic: Bicubic interpolation
• Lanczos2: Lanczos resampling with a=2
• Lanczos3: Lanczos resampling with a=3

Sample usage:

package main

import (
	"github.com/nfnt/resize"
	"image/jpeg"
	"log"
	"os"
)

func main() {
	// open "test.jpg"
	file, err := os.Open("test.jpg")
	if err != nil {
		log.Fatal(err)
	}

	// decode jpeg into image.Image
	img, err := jpeg.Decode(file)
	if err != nil {
		log.Fatal(err)
	}
	file.Close()

	// resize to width 1000 using Lanczos resampling
	// and preserve aspect ratio
	m := resize.Resize(1000, 0, img, resize.Lanczos3)

	out, err := os.Create("test_resized.jpg")
	if err != nil {
		log.Fatal(err)
	}
	defer out.Close()

	// write new image to file
	jpeg.Encode(out, m, nil)
}

TODO

• Implement low-pass filtering before downscaling to prevent moiré patterns in the resulting image
• Minimize calls to image.Image.At(): It's pretty slow but inevitable as it keeps the code generic

License

Copyright (c) 2012 Jan Schlicht janschlicht@gmail.com Resize is released under an MIT style license.