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package main
import (
"encoding/json"
"fmt"
"image"
"image/draw"
"image/png"
"io/ioutil"
"log"
"net/http"
"os"
"os/exec"
"path"
"time"
)
const (
level = 4
width = 550
delay = 8 // delay in hours, so that I can see daylight on my wallpaper during the day!
)
type latestData struct {
Date string `json:"date"`
File string `json:"file"`
}
func main() {
// Define work directory and files
var (
home = os.Getenv("HOME")
workDir = path.Join(home, ".himawari")
imageFile = path.Join(workDir, "/latest.png")
dataFile = path.Join(workDir, "/data")
data []byte
err error
oldData = new(latestData)
initData = new(latestData)
t time.Time
location *time.Location
output *image.RGBA
out *os.File
)
// Read the last date from dataFile if it exists
data, err = ioutil.ReadFile(dataFile)
if err != nil {
data = nil
} else {
err = json.Unmarshal(data, oldData)
if err != nil {
oldData = nil
}
}
// Get the data about the last image
err = getJSON("http://himawari8-dl.nict.go.jp/himawari8/img/D531106/latest.json", initData)
if err != nil {
log.Fatal("error getting json data from himawari server: ", err)
}
location, err = time.LoadLocation("Asia/Tokyo")
if err != nil {
log.Fatal("error loading Asia/Tokyo time zone data: ", err)
}
t, _ = time.ParseInLocation("2006-01-02 15:04:05", initData.Date, location)
if oldData != nil && oldData.Date == initData.Date {
log.Print("No new image, keeping the old one")
os.Exit(0)
}
t = t.Add(time.Duration(-delay) * time.Hour)
// Get all the chunks from the latest image and assemble them
output = image.NewRGBA(image.Rect(0, 0, level*width, level*width))
for x := 0; x < level; x++ {
for y := 0; y < level; y++ {
url := fmt.Sprintf("http://himawari8.nict.go.jp/img/D531106/%dd/%d/%s_%d_%d.png",
level, width, t.Format("2006/01/02/150405"), x, y)
var buff image.Image
err = getPNG(url, &buff)
if err != nil {
err = getPNG(url, &buff)
if err != nil {
log.Fatal("Error getting png :", url)
}
}
draw.Draw(output, image.Rect(x*width, y*width, (x+1)*width, (y+1)*width), buff, image.Point{0, 0}, draw.Src)
}
}
// Write output to file
out, err = os.Create(imageFile)
if err != nil {
err := os.Mkdir(workDir, 0755)
if err != nil {
log.Fatal("error creating output directory:", err)
}
out, err = os.Create(imageFile)
if err != nil {
log.Fatal("error creating output file:", err)
}
}
defer out.Close()
err = png.Encode(out, output)
if err != nil {
log.Fatal("Error writing output file:", err)
}
// Write dat file
buff, err := json.Marshal(initData)
ioutil.WriteFile(dataFile, buff, 0644)
// Exec feh
cmd := exec.Command("feh", "--bg-max", imageFile)
err = cmd.Run()
if err != nil {
log.Fatal("Error launching feh :", err)
}
}
func getJSON(url string, target interface{}) (err error) {
var r *http.Response
r, err = http.Get(url)
if err == nil {
defer r.Body.Close()
err = json.NewDecoder(r.Body).Decode(target)
}
return
}
func getPNG(url string, image *image.Image) (err error) {
var r *http.Response
r, err = http.Get(url)
if err == nil {
defer r.Body.Close()
*image, err = png.Decode(r.Body)
}
return
}
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