2020-08-17 13:19:06 +03:00
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/*
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2020-08-17 13:23:27 +03:00
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Copyright © 2020 Alexander Kiryukhin <a.kiryukhin@mail.ru>
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This file is part of StaticMap project.
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2020-08-17 13:19:06 +03:00
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*/
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2020-08-17 13:23:27 +03:00
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package static
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2020-08-17 13:19:06 +03:00
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import (
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"bytes"
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"fmt"
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"image"
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"image/color"
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"image/png"
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_ "image/png"
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"io/ioutil"
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"log"
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"math"
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"net/http"
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"sync"
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"github.com/disintegration/imaging"
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)
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const (
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tileAddr = `https://a.tile.openstreetmap.org/%d/%d/%d.png`
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tw = 256
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th = 256
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)
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func GetMapImage(lat, lon float64, zoom, width, height int) ([]byte, error) {
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x, y, dx, dy := getCoords(lat, lon, zoom)
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dst := imaging.New(width, height, color.NRGBA{0, 255, 0, 255})
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wg := sync.WaitGroup{}
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mu := sync.Mutex{}
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cx := width/2 - tw/2
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cy := height/2 - th/2
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sx := width/tw + 2
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sy := height/th + 2
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di := int(dx*float64(tw)) - tw/2
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dj := int(dy*float64(th)) - th/2
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for i := -sx / 2; i <= sx/2; i++ {
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for j := -sy / 2; j <= sy/2; j++ {
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wg.Add(1)
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go func(i, j int) {
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defer wg.Done()
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tile, err := getTile(x+i, y+j, zoom)
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if err != nil {
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log.Println(err)
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return
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}
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img, err := png.Decode(bytes.NewReader(tile))
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if err != nil {
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log.Println(err)
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return
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}
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mu.Lock()
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defer mu.Unlock()
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tx := cx + i*tw - di
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ty := cy + j*th - dj
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dst = imaging.Paste(dst, img, image.Pt(tx, ty))
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}(int(i), int(j))
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}
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}
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wg.Wait()
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out := bytes.NewBuffer([]byte{})
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if err := imaging.Encode(out, dst, imaging.PNG); err != nil {
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return nil, err
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}
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return out.Bytes(), nil
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}
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func getCoords(lat, lon float64, zoom int) (int, int, float64, float64) {
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x := (lon + 180.0) / 360.0 * (math.Exp2(float64(zoom)))
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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)))
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dx := x - math.Floor(x)
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dy := y - math.Floor(y)
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return int(math.Floor(x)), int(math.Floor(y)), dx, dy
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}
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func getTile(x, y, z int) ([]byte, error) {
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tile := fmt.Sprintf(tileAddr, z, x, y)
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resp, err := http.DefaultClient.Get(tile)
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if err != nil {
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return nil, err
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}
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defer resp.Body.Close()
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return ioutil.ReadAll(resp.Body)
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}
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