mapnikgenerate_tiles.py返回内存错误

Question

我正在尝试使用 generate_tiles.py 创建图块，每次运行时脚本，我收到以下错误：

线程 Thread-2 中出现异常： 回溯（最近一次调用最后一次）： 文件“/usr/lib/python2.7/threading.py”，第 552 行，位于 __bootstrap_inner 中 自我运行（） 文件“/usr/lib/python2.7/threading.py”，第 505 行，运行中 self.__target(*self.__args, **self.__kwargs) 文件“render_tiles.py”，第 114 行，循环中 self.render_tile(tile_uri, x, y, z) 文件“render_tiles.py”，第 96 行，在 render_tile 中 mapnik.render(self.m, im) 内存错误

这是我的脚本。

#!/usr/bin/python
from math import pi,cos,sin,log,exp,atan
from subprocess import call
import sys, os
from Queue import Queue
import mapnik
import threading
import random
import argparse

custom_fonts_dir = '/usr/share/fonts/'
mapnik.register_fonts(custom_fonts_dir)

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[int(zoom)]
         e = round(d[0] + float(ll[0]) * self.Bc[zoom])
         f = minmax(sin(DEG_TO_RAD * float(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.m = mapnik.Map(256, 256)
        self.printLock = printLock
        # Load style XML
        mapnik.load_map(self.m, mapfile)
        # Obtain  projection
        self.prj = mapnik.Projection(self.m.srs)
        # Projects between tile pixel co-ordinates and LatLong (EPSG:4326)
        self.tileproj = GoogleProjection(maxZoom+1)


    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)
        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):
        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 = Queue(32)
    printLock = threading.Lock()
    renderers = {}
    for i in range(num_threads):
        renderer = RenderThread(tile_dir, mapfile, queue, printLock, maxZoom)
        render_thread = threading.Thread(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)
        print "fromlattolon"

        # 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 = 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 = 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__":
    MIN_LON = '29.5732';
    MAX_LON = '35.0360';
    MIN_LAT = '-1.4840';
    MAX_LAT = '4.2144';
    bbox = ( MIN_LON, MIN_LAT,MAX_LON, MAX_LAT)
    style_file="/home/mossplix/projects/Dev/mapit/map/static/tilemill/uganda_districts.xml"
    tile_dir="/home/mossplix/projects/UnicefDev/mapit/map/static/tiles/"
    min_zoom=7
    max_zoom=14
    render_tiles(bbox, style_file, tile_dir, min_zoom, max_zoom)

这是mapnik配置文件 mapnik 配置 这是shapefile。我从源代码编译了mapnik，所以它应该很好。可能是什么问题？

Answer 1

我可以看出它最初是generate_tiles.py，稍作修改。

MemoryError 表示您正在请求渲染异常大的图像，或者您发现了 Mapnik bug。

由于前者更有可能，我认为您在修改 generate_tiles.py 时犯了一个错误。所以我拿了你的脚本，覆盖了 svn 中的最新版本，并找出了差异的差异： https://gist。 github.com/1197587。

在第 #106 行和第 #115 行，您可能需要使用 == 而不是 =，因为否则您将生成非常大的 x 和 y 值，这些值是无效的，并且可能是导致非常大的图像请求（对于给定的图块来说这是错误的）。

Answer 2

要生成的渲染线程的默认数量应大致等于可用 CPU 核心的数量
NUM_THREADS = 4

我在 NUM_THREADS=4 时遇到了完全相同的错误。
将 NUM_THREADS 的默认值更改为 1。我有一个 i5（4 核/每核 1 个线程），NUM_THREADS=4 非常不稳定。当 NUM_THREADS=1 时，它工作得很好。如果 NUM_THREADS=1 适合您，请尝试使用 NUM_THREADS=2 和 NUM_THREADS=3（如果没有崩溃）。