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)
}
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
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)
}