Pure golang image resizing

Go to file

Jason Summers cdbd68f34f Improve the way the new canvas size is calculated If both dimensions are given, always use those dimensions, avoiding roundoff error. If only one dimension is given, slightly prefer rounding the other dimension up, to rounding it down.		2012-11-27 20:49:01 -05:00
LICENSE	Documentation updated	2012-08-03 17:39:38 +02:00
README.md	Include samples in README.md	2012-11-14 22:08:45 +01:00
converter.go	Speed up computation: Try to avoid Image.At() as much as possible -> specialized color access for some image types	2012-09-21 20:02:25 +02:00
filters.go	Speed up computation: Try to avoid Image.At() as much as possible -> specialized color access for some image types	2012-09-21 20:02:25 +02:00
resize.go	Improve the way the new canvas size is calculated	2012-11-27 20:49:01 -05:00
resize_test.go	Speed up computation: Try to avoid Image.At() as much as possible -> specialized color access for some image types	2012-09-21 20:02:25 +02:00
sinc.go	initial commit	2012-08-02 21:59:40 +02:00
sinc_test.go	initial commit	2012-08-02 21:59:40 +02:00

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
MitchellNetravali: Mitchell-Netravali 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)
}

Downsizing Samples

Downsizing is not as simple as it might look like. Images have to be filtered before they are scaled down, otherwise aliasing might occur. Filtering is highly subjective: Applying too much will blur the whole image, too little will make aliasing become apparent. Resize tries to provide sane defaults that should suffice in most cases.