1 files changed, 88 insertions, 0 deletions
diff --git a/pkg/static/map.go b/pkg/static/map.go
new file mode 100644
index 0000000..2597aaf
--- /dev/null
+++ b/pkg/static/map.go
@@ -0,0 +1,88 @@
+/*
+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) ([]byte, 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))
+			}(int(i), int(j))
+		}
+	}
+	wg.Wait()
+
+	out := bytes.NewBuffer([]byte{})
+	if err := imaging.Encode(out, dst, 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)
+}