generate_tiles_multiprocess.py

#!/usr/bin/env python
from math import pi,cos,sin,log,exp,atan
from subprocess import call
import sys, os
import multiprocessing

try:
    import mapnik2 as mapnik
except:
    import mapnik

DEG_TO_RAD = pi/180
RAD_TO_DEG = 180/pi

# Default number of rendering threads to spawn, should be roughly equal to number of CPU cores available
NUM_THREADS = 4


def minmax (a,b,c):
    a = max(a,b)
    a = min(a,c)
    return a

class GoogleProjection:
    def __init__(self,levels=18):
        self.Bc = []
        self.Cc = []
        self.zc = []
        self.Ac = []
        c = 256
        for d in range(0,levels):
            e = c/2;
            self.Bc.append(c/360.0)
            self.Cc.append(c/(2 * pi))
            self.zc.append((e,e))
            self.Ac.append(c)
            c *= 2
                
    def fromLLtoPixel(self,ll,zoom):
         d = self.zc[zoom]
         e = round(d[0] + ll[0] * self.Bc[zoom])
         f = minmax(sin(DEG_TO_RAD * ll[1]),-0.9999,0.9999)
         g = round(d[1] + 0.5*log((1+f)/(1-f))*-self.Cc[zoom])
         return (e,g)
     
    def fromPixelToLL(self,px,zoom):
         e = self.zc[zoom]
         f = (px[0] - e[0])/self.Bc[zoom]
         g = (px[1] - e[1])/-self.Cc[zoom]
         h = RAD_TO_DEG * ( 2 * atan(exp(g)) - 0.5 * pi)
         return (f,h)



class RenderThread:
    def __init__(self, tile_dir, mapfile, q, printLock, maxZoom):
        self.tile_dir = tile_dir
        self.q = q
        self.mapfile = mapfile
        self.maxZoom = maxZoom
        self.printLock = printLock

    def render_tile(self, tile_uri, x, y, z):
        # Calculate pixel positions of bottom-left & top-right
        p0 = (x * 256, (y + 1) * 256)
        p1 = ((x + 1) * 256, y * 256)

        # Convert to LatLong (EPSG:4326)
        l0 = self.tileproj.fromPixelToLL(p0, z);
        l1 = self.tileproj.fromPixelToLL(p1, z);

        # Convert to map projection (e.g. mercator co-ords EPSG:900913)
        c0 = self.prj.forward(mapnik.Coord(l0[0],l0[1]))
        c1 = self.prj.forward(mapnik.Coord(l1[0],l1[1]))

        # Bounding box for the tile
        if hasattr(mapnik,'mapnik_version') and mapnik.mapnik_version() >= 800:
            bbox = mapnik.Box2d(c0.x,c0.y, c1.x,c1.y)
        else:
            bbox = mapnik.Envelope(c0.x,c0.y, c1.x,c1.y)
        render_size = 256
        self.m.resize(render_size, render_size)
        self.m.zoom_to_box(bbox)
        if(self.m.buffer_size < 128):
            self.m.buffer_size = 128

        # Render image with default Agg renderer
        im = mapnik.Image(render_size, render_size)
        mapnik.render(self.m, im)
        im.save(tile_uri, 'png256')


    def loop(self):
        
        self.m = mapnik.Map(256, 256)
        # Load style XML
        mapnik.load_map(self.m, self.mapfile, True)
        # Obtain <Map> projection
        self.prj = mapnik.Projection(self.m.srs)
        # Projects between tile pixel co-ordinates and LatLong (EPSG:4326)
        self.tileproj = GoogleProjection(self.maxZoom+1)
                
        while True:
            #Fetch a tile from the queue and render it
            r = self.q.get()
            if (r == None):
                self.q.task_done()
                break
            else:
                (name, tile_uri, x, y, z) = r

            exists= ""
            if os.path.isfile(tile_uri):
                exists= "exists"
            else:
                self.render_tile(tile_uri, x, y, z)
            bytes=os.stat(tile_uri)[6]
            empty= ''
            if bytes == 103:
                empty = " Empty Tile "
            self.printLock.acquire()
            print name, ":", z, x, y, exists, empty
            self.printLock.release()
            self.q.task_done()



def render_tiles(bbox, mapfile, tile_dir, minZoom=1,maxZoom=18, name="unknown", num_threads=NUM_THREADS):
    print "render_tiles(",bbox, mapfile, tile_dir, minZoom,maxZoom, name,")"

    # Launch rendering threads
    queue = multiprocessing.JoinableQueue(32)
    printLock = multiprocessing.Lock()
    renderers = {}
    for i in range(num_threads):
        renderer = RenderThread(tile_dir, mapfile, queue, printLock, maxZoom)
        render_thread = multiprocessing.Process(target=renderer.loop)
        render_thread.start()
        #print "Started render thread %s" % render_thread.getName()
        renderers[i] = render_thread

    if not os.path.isdir(tile_dir):
         os.mkdir(tile_dir)

    gprj = GoogleProjection(maxZoom+1) 

    ll0 = (bbox[0],bbox[3])
    ll1 = (bbox[2],bbox[1])

    for z in range(minZoom,maxZoom + 1):
        px0 = gprj.fromLLtoPixel(ll0,z)
        px1 = gprj.fromLLtoPixel(ll1,z)

        # check if we have directories in place
        zoom = "%s" % z
        if not os.path.isdir(tile_dir + zoom):
            os.mkdir(tile_dir + zoom)
        for x in range(int(px0[0]/256.0),int(px1[0]/256.0)+1):
            # Validate x co-ordinate
            if (x < 0) or (x >= 2**z):
                continue
            # check if we have directories in place
            str_x = "%s" % x
            if not os.path.isdir(tile_dir + zoom + '/' + str_x):
                os.mkdir(tile_dir + zoom + '/' + str_x)
            for y in range(int(px0[1]/256.0),int(px1[1]/256.0)+1):
                # Validate x co-ordinate
                if (y < 0) or (y >= 2**z):
                    continue
                str_y = "%s" % y
                tile_uri = tile_dir + zoom + '/' + str_x + '/' + str_y + '.png'
                # Submit tile to be rendered into the queue
                t = (name, tile_uri, x, y, z)
                queue.put(t)

    # Signal render threads to exit by sending empty request to queue
    for i in range(num_threads):
        queue.put(None)
    # wait for pending rendering jobs to complete
    queue.join()
    for i in range(num_threads):
        renderers[i].join()



if __name__ == "__main__":
	
    home = os.environ['HOME']
    try:
        mapfile = os.environ['MAPNIK_MAP_FILE']
    except KeyError:
        mapfile = home + "/svn.openstreetmap.org/applications/rendering/mapnik/osm-local.xml"
    try:
        tile_dir = os.environ['MAPNIK_TILE_DIR']
    except KeyError:
        tile_dir = home + "/osm/tiles/"

    if not tile_dir.endswith('/'):
        tile_dir = tile_dir + '/'

    #-------------------------------------------------------------------------
    #
    # Change the following for different bounding boxes and zoom levels
    #
    # Start with an overview
    # World
    bbox = (-180.0,-90.0, 180.0,90.0)

    render_tiles(bbox, mapfile, tile_dir, 0, 5, "World")

    minZoom = 10
    maxZoom = 16
    bbox = (-2, 50.0,1.0,52.0)
    render_tiles(bbox, mapfile, tile_dir, minZoom, maxZoom)

    # Muenchen
    bbox = (11.4,48.07, 11.7,48.22)
    render_tiles(bbox, mapfile, tile_dir, 1, 12 , "Muenchen")

    # Muenchen+
    bbox = (11.3,48.01, 12.15,48.44)
    render_tiles(bbox, mapfile, tile_dir, 7, 12 , "Muenchen+")

    # Muenchen++
    bbox = (10.92,47.7, 12.24,48.61)
    render_tiles(bbox, mapfile, tile_dir, 7, 12 , "Muenchen++")

    # Nuernberg
    bbox=(10.903198,49.560441,49.633534,11.038085)
    render_tiles(bbox, mapfile, tile_dir, 10, 16, "Nuernberg")

    # Karlsruhe
    bbox=(8.179113,48.933617,8.489252,49.081707)
    render_tiles(bbox, mapfile, tile_dir, 10, 16, "Karlsruhe")

    # Karlsruhe+
    bbox = (8.3,48.95,8.5,49.05)
    render_tiles(bbox, mapfile, tile_dir, 1, 16, "Karlsruhe+")

    # Augsburg
    bbox = (8.3,48.95,8.5,49.05)
    render_tiles(bbox, mapfile, tile_dir, 1, 16, "Augsburg")

    # Augsburg+
    bbox=(10.773251,48.369594,10.883834,48.438577)
    render_tiles(bbox, mapfile, tile_dir, 10, 14, "Augsburg+")

    # Europe+
    bbox = (1.0,10.0, 20.6,50.0)
    render_tiles(bbox, mapfile, tile_dir, 1, 11 , "Europe+")