From cf7a05f80f68b5b1c8bcc0089679dd497cec2506 Mon Sep 17 00:00:00 2001 From: =Corey Hulen Date: Sun, 14 Jun 2015 23:53:32 -0800 Subject: first commit --- .../src/github.com/nfnt/resize/README.md | 149 +++++++++++++++++++++ 1 file changed, 149 insertions(+) create mode 100644 Godeps/_workspace/src/github.com/nfnt/resize/README.md (limited to 'Godeps/_workspace/src/github.com/nfnt/resize/README.md') diff --git a/Godeps/_workspace/src/github.com/nfnt/resize/README.md b/Godeps/_workspace/src/github.com/nfnt/resize/README.md new file mode 100644 index 000000000..2aefa75c9 --- /dev/null +++ b/Godeps/_workspace/src/github.com/nfnt/resize/README.md @@ -0,0 +1,149 @@ +Resize +====== + +Image resizing for the [Go programming language](http://golang.org) with common interpolation methods. + +[![Build Status](https://travis-ci.org/nfnt/resize.svg)](https://travis-ci.org/nfnt/resize) + +Installation +------------ + +```bash +$ go get github.com/nfnt/resize +``` + +It's that easy! + +Usage +----- + +This package needs at least Go 1.1. Import package with + +```go +import "github.com/nfnt/resize" +``` + +The resize package provides 2 functions: + +* `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.Thumbnail` downscales 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. + +```go +resize.Resize(width, height uint, img image.Image, interp resize.InterpolationFunction) image.Image +resize.Thumbnail(maxWidth, maxHeight uint, img image.Image, interp resize.InterpolationFunction) image.Image +``` + +The provided interpolation functions are (from fast to slow execution time) + +- `NearestNeighbor`: [Nearest-neighbor interpolation](http://en.wikipedia.org/wiki/Nearest-neighbor_interpolation) +- `Bilinear`: [Bilinear interpolation](http://en.wikipedia.org/wiki/Bilinear_interpolation) +- `Bicubic`: [Bicubic interpolation](http://en.wikipedia.org/wiki/Bicubic_interpolation) +- `MitchellNetravali`: [Mitchell-Netravali interpolation](http://dl.acm.org/citation.cfm?id=378514) +- `Lanczos2`: [Lanczos resampling](http://en.wikipedia.org/wiki/Lanczos_resampling) with a=2 +- `Lanczos3`: [Lanczos resampling](http://en.wikipedia.org/wiki/Lanczos_resampling) with a=3 + +Which of these methods gives the best results depends on your use case. + +Sample usage: + +```go +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) +} +``` + +Caveats +------- + +* Optimized access routines are used for `image.RGBA`, `image.NRGBA`, `image.RGBA64`, `image.NRGBA64`, `image.YCbCr`, `image.Gray`, and `image.Gray16` types. All other image types are accessed in a generic way that will result in slow processing speed. +* JPEG images are stored in `image.YCbCr`. This image format stores data in a way that will decrease processing speed. A resize may be up to 2 times slower than with `image.RGBA`. + + +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. + +### Artificial sample + +Original image +![Rings](http://nfnt.github.com/img/rings_lg_orig.png) + + + + + + + + + + + + + + +

Nearest-Neighbor
Bilinear

Bicubic
Mitchell-Netravali

Lanczos2
Lanczos3
+ +### Real-Life sample + +Original image +![Original](http://nfnt.github.com/img/IMG_3694_720.jpg) + + + + + + + + + + + + + + +

Nearest-Neighbor
Bilinear

Bicubic
Mitchell-Netravali

Lanczos2
Lanczos3
+ + +License +------- + +Copyright (c) 2012 Jan Schlicht +Resize is released under a MIT style license. -- cgit v1.2.3-1-g7c22