Golang 轻量级的图片服务器.rar

# This package is no longer being updated! Please look for alternatives if that bothers you. Resize ====== Image resizing for the [Go programming language](http://golang.org) with common interpolation methods. [](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  <table> <tr> <th><img src="http://nfnt.github.com/img/rings_300_NearestNeighbor.png" /><br>Nearest-Neighbor</th> <th><img src="http://nfnt.github.com/img/rings_300_Bilinear.png" /><br>Bilinear</th> </tr> <tr> <th><img src="http://nfnt.github.com/img/rings_300_Bicubic.png" /><br>Bicubic</th> <th><img src="http://nfnt.github.com/img/rings_300_MitchellNetravali.png" /><br>Mitchell-Netravali</th> </tr> <tr> <th><img src="http://nfnt.github.com/img/rings_300_Lanczos2.png" /><br>Lanczos2</th> <th><img src="http://nfnt.github.com/img/rings_300_Lanczos3.png" /><br>Lanczos3</th> </tr> </table> ### Real-Life sample Original image  <table> <tr> <th><img src="http://nfnt.github.com/img/IMG_3694_300_NearestNeighbor.png" /><br>Nearest-Neighbor</th> <th><img src="http://nfnt.github.com/img/IMG_3694_300_Bilinear.png" /><br>Bilinear</th> </tr> <tr> <th><img src="http://nfnt.github.com/img/IMG_3694_300_Bicubic.png" /><br>Bicubic</th> <th><img src="http://nfnt.github.com/img/IMG_3694_300_MitchellNetravali.png" /><br>Mitchell-Netravali</th> </tr> <tr> <th><img src="http://nfnt.github.com/img/IMG_3694_300_Lanczos2.png" /><br>Lanczos2</th> <th><img src="http://nfnt.github.com/img/IMG_3694_300_Lanczos3.png" /><br>Lanczos3</th> </tr> </table> License ------- Copyright (c) 2012 Jan Schlicht <janschlicht@gmail.com> Resize is released under a MIT style license.