Go实战--golang实现生成缩略图服务器(disintegration/imaging、nfnt/resize)

生命不止，继续 go go go~~~~

今天做一点图片处理的东西，跟大家一起学习分享。

很久之前，介绍过golang提供的关于图片的标准库：

Go语言学习之image、image/color、image/png、image/jpeg包(the way to go)

当你search on google或百度一下的时候，你会发现很多提到了graphics-go/graphics，但是这个库不知道为何，官方好像不再提供了，很难找到了。

那也没关系，我们还有面向github编程呢！！！

温故而知新，先看一下之前的代码：

生成图片

package main

import "image"
import "image/color"
import "image/png"
import "os"

func main() {
// Create an 100 x 50 image
img := image.NewRGBA(image.Rect(0, 0, 100, 50))

// Draw a red dot at (2, 3)
img.Set(2, 3, color.RGBA{255, 0, 0, 255})

// Save to out.png
f, _ := os.OpenFile("out.png", os.O_WRONLY|os.O_CREATE, 0600)
defer f.Close()
png.Encode(f, img)
}

disintegration/imaging

github地址：

https://github.com/disintegration/imaging

Star: 1284

获取：

go get -u github.com/disintegration/imaging

生成缩略图

下面的代码，将三张图片生成一张缩略图。

出自：

https://www.socketloop.com/tutorials/golang-generate-thumbnails-from-images

package main

import (
"image"
"image/color"
"runtime"

"github.com/disintegration/imaging"
)

func main() {
// use all CPU cores for maximum performance
runtime.GOMAXPROCS(runtime.NumCPU())

// input files
files := []string{"1.jpg", "2.jpg", "3.jpg"}

// load images and make 100x100 thumbnails of them
var thumbnails []image.Image
for _, file := range files {
img, err := imaging.Open(file)
if err != nil {
panic(err)
}
thumb := imaging.Thumbnail(img, 100, 100, imaging.CatmullRom)
thumbnails = append(thumbnails, thumb)
}

// create a new blank image
dst := imaging.New(100*len(thumbnails), 100, color.NRGBA{0, 0, 0, 0})

// paste thumbnails into the new image side by side
for i, thumb := range thumbnails {
dst = imaging.Paste(dst, thumb, image.Pt(i*100, 0))
}

// save the combined image to file
err := imaging.Save(dst, "dst.jpg")
if err != nil {
panic(err)
}
}

生成缩略图服务

接下来，根据用户提供的url，生成不同尺寸的缩略图。

关于golang中net/http可以参考：

Go语言学习之net/http包(The way to go)

package main

import (
"fmt"
"image"
"image/color"
"image/png"
"net/http"
"runtime"
"strconv"
"strings"

"github.com/disintegration/imaging"
)

func main() {
// use all CPU cores for maximum performance
runtime.GOMAXPROCS(runtime.NumCPU())
http.HandleFunc("/", doImageHandler)
http.ListenAndServe("localhost:8080", nil)
}
func doImageHandler(w http.ResponseWriter, r *http.Request) {
fmt.Printf("%q\n", strings.Split(r.URL.Path, "/"))
url := strings.Split(r.URL.Path, "/")
if len(url) != 3 {
return
}

thumbnails_size := strings.Split(url[2], "_")
if len(thumbnails_size) != 2 {
return
}
thumbnails_width, _ := strconv.Atoi(thumbnails_size[0])
thumbnails_height, _ := strconv.Atoi(thumbnails_size[1])

img, err := imaging.Open(url[1])
if err != nil {
panic(err)
}
thumb := imaging.Thumbnail(img, thumbnails_width, thumbnails_height, imaging.CatmullRom)
dst := imaging.New(thumbnails_width, thumbnails_height, color.NRGBA{0, 0, 0, 0})
dst = imaging.Paste(dst, thumb, image.Pt(0, 0))

if err != nil {
panic(err)
}
header := w.Header()
header.Add("Content-Type", "image/jpeg")

png.Encode(w, dst)
}

例如，浏览器输入：http://localhost:8080/1.jpg/80_90

就会生成一张80*90的1.jpg的缩略图

nfnt/resize

github地址:

https://github.com/nfnt/resize

Star: 1544

获取：

go get github.com/nfnt/resize

等比例放大缩小图片

package main

import (
"image/jpeg"
"log"
"os"

"github.com/nfnt/resize"
)

func main() {
file, err := os.Open("1.jpg")
if err != nil {
log.Fatal(err)
}

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(100, 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)
}