OpenStreetMap Server

[alexfish]

HI All

as part of the on going XCB cairo / surfaces

it will be map enabled Hence this bit

How to get the tiles from openstreet map

You will need curl.bac From HERE

The FUNCTIONS + a sample in Main

objective Create the Zoom Directory , create Zoom level Directories
how to identity where the png are
read from the terminal
EXAMPLE

INCLUDE "curl.bac"

DEF FN ASINH = asinh
DEF FN ATAN = atan
'radius at equater
DEF FN OSM_EQ_RADIUS =  6378137.0
DEF FN ISNAN = isnan
DECLARE OSMDIR$ TYPE STRING

' https://wiki.openstreetmap.org/wiki/Slippy_map_tilenames
' source$ server [a,b,c]
'  ========================================================
'  ========================================================
FUNCTION LONG_TO_PIX(int ZOOM, double longditude) TYPE int
LOCAL TILE_X TYPE int
TILE_X = (int)(FLOOR(( longditude +180.0) /360 *(1 << ZOOM)))
RETURN TILE_X

END FUNCTION

' =====================================================
FUNCTION LAT_TO_PIX(int ZOOM, double latitude) TYPE int

LOCAL TILE_Y TYPE int
LOCAL LAT_RAD TYPE double

LAT_RAD = latitude * PI / 180

TILE_Y = (int)FLOOR( (1.0 - ASINH(TAN(LAT_RAD)) / PI) / 2.0 * (1 << ZOOM))
RETURN TILE_Y

END FUNCTION

' =====================================================
FUNCTION TILE_X_TO_LONG(int x, int z) TYPE double

RETURN x / (double)(1 << z) * 360.0 - 180

END FUNCTION

' =====================================================
FUNCTION TILE_Y_TO_LAT(int y, int z) TYPE double

LOCAL n TYPE double
n = PI - 2.0 * PI * y / (double)(1 << z)
RETURN 180.0 / PI * ATAN(0.5 * (exp(n) - exp(-n)))

END FUNCTION
' =====================================================

FUNCTION CHECK_NAN(float numb) TYPE STRING
IF ( ISNAN(numb)) THEN
RETURN "NAN"
ELSE
RETURN STR$(numb)
END IF
END FUNCTION
' =====================================================

FUNCTION OSM_GET_TILE$ (int ZOOM, double longditude, double latitude, STRING source$) TYPE STRING


LOCAL  filename$ TYPE STRING
filename$ =OSMDIR$ & STR$(ZOOM)

LOCAL TILE$ TYPE STRING
LOCAL TILE_X, TILE_Y TYPE int
LOCAL LAT_RAD TYPE double

TILE_X = LONG_TO_PIX(ZOOM,longditude)
TILE_Y = LAT_TO_PIX(ZOOM,latitude)

TILE$ = "https://" & source$  & ".tile.openstreetmap.org/" & STR$(ZOOM) & "/" & STR$(TILE_X) & "/" & STR$(TILE_Y) & ".png"

MAKEDIR OSMDIR$ & STR$(ZOOM) & "/" & STR$(TILE_X)
filename$ =OSMDIR$ & STR$(ZOOM) & "/" & STR$(TILE_X) &  "/" & STR$(TILE_Y) & ".png"
IF ( NOT(FILEEXISTS (filename$ ))) THEN
'PRINT "GET TILE:" ,TILE$

OPEN filename$ FOR WRITING AS download

easyhandle = curl_easy_init()
curl_global_init(CURL_GLOBAL_ALL)
curl_easy_setopt(easyhandle, CURLOPT_USERAGENT, "bacon-osm-map")
curl_easy_setopt(easyhandle, CURLOPT_SSL_VERIFYHOST, 2L)
curl_easy_setopt(easyhandle, CURLOPT_URL,TILE$)
curl_easy_setopt(easyhandle, CURLOPT_WRITEFUNCTION, NULL)
'curl_easy_setopt(easyhandle, CURLOPT_FOLLOWLOCATION, 1L);
curl_easy_setopt(easyhandle, CURLOPT_WRITEDATA, download)

success = curl_easy_perform(easyhandle)
' Cleanup
curl_easy_cleanup(easyhandle)

' Close filehandle
CLOSE FILE download
RETURN filename$
ELSE
RETURN filename$
END IF

END FUNCTION

'  ========================================================
SUB SET_OSM_DIRECTORY()

HOME$ = GETENVIRON$("HOME")
OSMDIR$ = HOME$ & "/bacon-osm-maps/"
'PRINT OSMDIR$
'MAKEDIR OSMDIR$

FOR t = 1 TO 19
MAKEDIR OSMDIR$ & STR$(t)
OPEN OSMDIR$ & STR$(t) & "/zoom" FOR WRITING AS myfile
WRITELN "bacon-osm-" & STR$(t) TO myfile
CLOSE FILE myfile
NEXT

END SUB



' MAIN EXAMPLE =============================================

LOCAL TILE$
LOCAL SERVER_SOURCE$ TYPE STRING
LOCAL lat, lon TYPE double

LOCAL nan$ TYPE STRING

SET_OSM_DIRECTORY()

lon = -0.1278
lat = 51.5074
' normaly algos may return a nan on float a nan can couse seg fault check for is nan
nan$ = CHECK_NAN(lat)
IF nan$ = "NAN" THEN END

nan$ = CHECK_NAN(lon)
IF nan$ = "NAN" THEN END

' discriptor source$ server [a,b,c].tile
SERVER_SOURCE$ = "a"


'get tile ZOOM , LONGITUDE , LATITUDE oms server discriptor
' London tile zoom 10 longitude latitude

TILE$ = OSM_GET_TILE$(10,lon,lat,"a")

'TILE$ = OSM_GET_TILE$(10,-4.01,51.4934,"b")
'TILE$ = OSM_GET_TILE$(10,-4.01,51.4934,"c")


' Lat  SOUTH - 0 + NORTH
' Long WEST -  0  +  EAST  IE greenwich london 51.4934° N, 0.0098° E
PRINT TILE$

Screenshot ::

London latitude 51.5074° N, 0.1278° W
actual cords
zoom 10
lon = -0.1278
lat = 51.5074

Attachments:

[vovchik]

Dear Alex,

Thanks. Working for me. And, when I change lat and lon, I get the correct new locations...at least in Europe (so far).

With kind regards,
vovchik

[alexfish]

Hi Vovchik

Thanks for Testing

I did note the original code had lat and long wrongly placed

hence corrected the code ; to be geo correct:

BR
Alex

[alexfish]

Hi All


Update to the functions

Now in separate Cod Block

+ Added Tile to position

TILE_X_TO_LONG & TILE_Y_TO_LAT

BR
Alex