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/*
Copyright © 2020 Alexander Kiryukhin <a.kiryukhin@mail.ru>
This file is part of StaticMap project.
*/
package static
import (
"bytes"
"fmt"
"image"
"image/color"
"image/png"
_ "image/png"
"io/ioutil"
"log"
"math"
"net/http"
"sync"
"github.com/disintegration/imaging"
)
const (
tileAddr = `https://a.tile.openstreetmap.org/%d/%d/%d.png`
tw = 256
th = 256
)
func GetMapImage(lat, lon float64, zoom, width, height int) (image.Image, error) {
x, y, dx, dy := getCoords(lat, lon, zoom)
dst := imaging.New(width, height, color.NRGBA{0, 255, 0, 255})
wg := sync.WaitGroup{}
mu := sync.Mutex{}
cx := width/2 - tw/2
cy := height/2 - th/2
sx := width/tw + 2
sy := height/th + 2
di := int(dx*float64(tw)) - tw/2
dj := int(dy*float64(th)) - th/2
for i := -sx / 2; i <= sx/2; i++ {
for j := -sy / 2; j <= sy/2; j++ {
wg.Add(1)
go func(i, j int) {
defer wg.Done()
tile, err := getTile(x+i, y+j, zoom)
if err != nil {
log.Println(err)
return
}
img, err := png.Decode(bytes.NewReader(tile))
if err != nil {
log.Println(err)
return
}
mu.Lock()
defer mu.Unlock()
tx := cx + i*tw - di
ty := cy + j*th - dj
dst = imaging.Paste(dst, img, image.Pt(tx, ty))
}(i, j)
}
}
wg.Wait()
return dst, nil
}
func AsBytes(image image.Image) ([]byte,error) {
out := bytes.NewBuffer([]byte{})
if err := imaging.Encode(out, image, imaging.PNG); err != nil {
return nil, err
}
return out.Bytes(), nil
}
func getCoords(lat, lon float64, zoom int) (int, int, float64, float64) {
x := (lon + 180.0) / 360.0 * (math.Exp2(float64(zoom)))
y := (1.0 - math.Log(math.Tan(lat*math.Pi/180.0)+1.0/math.Cos(lat*math.Pi/180.0))/math.Pi) / 2.0 * (math.Exp2(float64(zoom)))
dx := x - math.Floor(x)
dy := y - math.Floor(y)
return int(math.Floor(x)), int(math.Floor(y)), dx, dy
}
func getTile(x, y, z int) ([]byte, error) {
tile := fmt.Sprintf(tileAddr, z, x, y)
resp, err := http.DefaultClient.Get(tile)
if err != nil {
return nil, err
}
defer resp.Body.Close()
return ioutil.ReadAll(resp.Body)
}
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