forked from gaoyifan/GDEM-server
/
main.go
163 lines (150 loc) · 3.67 KB
/
main.go
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package main
import (
"encoding/binary"
"fmt"
"github.com/gorilla/mux"
"github.com/hashicorp/golang-lru"
"image"
"image/png"
"math"
"net/http"
"os"
"runtime"
"strconv"
)
var (
prefix string = "map/ASTGTM2_"
suffix string = "_dem.png"
imageCache *lru.Cache
imageCacheLen int = 20
)
type Point struct {
lon, lat float64
}
type PointInt struct {
lon, lat int
}
func (c Point) toInt() PointInt {
var r PointInt
r.lat = (int)(c.lat)
r.lon = (int)(c.lon)
return r
}
func init() {
var err error
runtime.GOMAXPROCS(runtime.NumCPU())
imageCache, err = lru.New(imageCacheLen)
if err != nil {
fmt.Println(err)
}
}
func XYToLonLat(xtile, ytile int, zoom uint) Point {
var lon_deg, lat_deg float64
var rt Point
b := (1 << zoom)
n := float64(b)
lon_deg = (float64)(xtile*360)/n - 180
lat_deg = math.Atan(math.Sinh(math.Pi*(1-2*(float64)(ytile)/n))) * 180 / math.Pi
rt.lon = lon_deg
rt.lat = lat_deg
return rt
}
func lnglatToXY(longitude, latitude float64, zoom int) (int, int) {
lat_rad := latitude * math.Pi / 180
n := 1 << (uint)(zoom)
xtile := (int)(math.Floor((longitude + 180) / 360 * (float64)(n)))
ytile := (int)((1 - math.Log(math.Tan(lat_rad)+1/math.Cos(lat_rad))/math.Pi) * (float64)(n) / 2)
return xtile, ytile
}
func getImageFileName(p PointInt) string {
var (
lat_dir, lon_dir string
)
if p.lat >= 0 {
lat_dir = "N"
} else {
lat_dir = "S"
}
if p.lon >= 0 {
lon_dir = "E"
} else {
lon_dir = "W"
}
return fmt.Sprintf("%s%s%d%s%d%s", prefix, lat_dir, p.lat, lon_dir, p.lon, suffix)
}
func getImage(p Point) image.Image {
pInt := p.toInt()
img, cached := imageCache.Get(pInt)
if !cached {
file, err := os.Open(getImageFileName(pInt))
if err != nil {
return nil
}
defer file.Close()
img, err = png.Decode(file)
if err != nil {
return nil
}
imageCache.Add(pInt, img)
}
return img.(image.Image)
}
func mapHandler(w http.ResponseWriter, r *http.Request) {
var (
i0, j0, size_index, zoomi int
zoom uint
latSpan, lonSpan float64
err error
)
para := mux.Vars(r)
if i0, err = strconv.Atoi(para["i"]); err != nil {
return
}
if j0, err = strconv.Atoi(para["j"]); err != nil {
return
}
if zoomi, err = strconv.Atoi(para["zoom"]); err != nil {
return
}
zoom = uint(zoomi)
if size_index, err = strconv.Atoi(para["size"]); err != nil {
return
}
pStart := XYToLonLat(i0, j0, zoom)
pEnd := XYToLonLat(i0+1, j0+1, zoom)
fmt.Printf("%f\t%f\t%f\t%f\t", pStart.lat, pStart.lon, pEnd.lat, pEnd.lon)
fmt.Println(r.URL)
size := 1 << (uint)(size_index)
latSpan = (pEnd.lat - pStart.lat) / (float64)(size)
lonSpan = (pEnd.lon - pStart.lon) / (float64)(size)
for i := 0; i <= size; i++ {
var p Point
p.lat = pStart.lat + (float64)(i)*latSpan
for j := 0; j <= size; j++ {
p.lon = pStart.lon + (float64)(j)*lonSpan
img := getImage(p)
if img == nil {
binary.Write(w, binary.LittleEndian, float32(0))
continue
}
x := (int)((p.lat - math.Floor(p.lat)) * (float64)(img.Bounds().Max.X))
//y := (int)((p.lon - math.Floor(p.lon)) * (float64)(img.Bounds().Max.Y))
y := img.Bounds().Max.Y - (int)((p.lon-math.Floor(p.lon))*(float64)(img.Bounds().Max.Y))
gray, _, _, _ := img.At(x, y).RGBA()
binary.Write(w, binary.LittleEndian, float32(int16(gray)))
//w.Write([]byte(strconv.Itoa((int)((int16)(gray)))))
//w.Write([]byte("\t"))
}
//w.Write([]byte("\n"))
}
}
func main() {
route := mux.NewRouter()
route.HandleFunc("/{i:[0-9]+}/{j:[0-9]+}/{zoom:[0-9]+}/{size:[0-9]+}", mapHandler).Methods("GET")
http.Handle("/", route)
err := http.ListenAndServe(":8000", nil)
if err != nil {
fmt.Println(err)
}
//fmt.Println(lnglatToXY(119, 40, 17))
}