README.md

About

Pure golang image resizing.

This package is a fork of https://github.com/nfnt/resize , required Go >=1.12+.

Usage

Fetch package go get github.com/giant-store/goimg

Example: resize a JPEG image

import (
	"bytes"
	"fmt"
	"image"
	"image/jpeg"
	"io/ioutil"
	"log"
	"os"

	"github.com/giant-stone/goimg"
)

func main() {
	// fetch sample image form https://en.wikipedia.org/wiki/Lenna
	fn := "Lena.jpg"
	dat, err := ioutil.ReadFile(fn)
	exitOnErr(err)

	img, format, err := image.Decode(bytes.NewReader(dat))
	exitOnErr(err)

	widthOrigin, heightOrigin := img.Bounds().Max.X, img.Bounds().Max.Y
	width, height := uint(widthOrigin/2), uint(heightOrigin/2)
	imgResized := goimg.Resize(width, height, img, goimg.Lanczos3)

	output, err := os.Create("small.jpg")
	exitOnErr(err)
	defer output.Close()

	err = jpeg.Encode(output, imgResized, nil)
	exitOnErr(err)

	fmt.Printf("resize format=%s (%d,%d)=>(%d,%d) \n", format, widthOrigin, heightOrigin, width, height)
}

func exitOnErr(err error) {
	if err != nil {
		log.Panic(err)
	}
}

The goimg package provides 2 functions:

• goimg.Resize creates a scaled image with new dimensions (width, height) using the interpolation function i. If either width or height is set to 0, it will be set to an aspect ratio preserving value.
• goimg.Thumbnail down-scales an image preserving its aspect ratio to the maximum dimensions (maxWidth, maxHeight). It will return the original image if original sizes are smaller than the provided dimensions.

goimg.Resize(width, height uint, img image.Image, i goimg.InterpolationFunction) image.Image
goimg.Thumbnail(maxWidth, maxHeight uint, img image.Image, i goimg.InterpolationFunction) image.Image

The provided interpolation functions are (from fast to slow execution time)

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

Which of these methods gives the best results depends on your use case.