Python底图在缩放时更改分辨率

Question

当用户放大以节省内存和处理时间时，我正在尝试更改地图的分辨率。我已经尝试了以下代码，但即使每次缩放时地图分辨率都会发生变化，图形也不会更新，我仍然坚持使用粗分辨率。有关如何在用户缩放时强制地图更新其分辨率的任何想法？谢谢！

这是我尝试过的代码：

from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt

# create new figure, axes instances
fig = plt.figure(dpi=150)
ax = fig.add_axes([0.1,0.1,0.8,0.8])
# setup mercator map projection
map = Basemap(projection='merc',llcrnrlat=-58,urcrnrlat=80,
              llcrnrlon=-180,urcrnrlon=180,resolution='c')

map.drawcoastlines(linewidth=0.50)
map.fillcontinents()
map.drawmapboundary()

# Declare and register callbacks for zoom control
def on_lims_change(axes):
    xrange = abs(ax.get_xlim()[1] - ax.get_xlim()[0])
    yrange = abs(ax.get_xlim()[1] - ax.get_xlim()[0])

    # try to change map resolution based on zoom level
    if max(xrange,yrange) < 1E7 and max(xrange,yrange) > 1E6: # 'l' = low
        map.resolution = 'l'
    elif max(xrange,yrange) < 1E6 and max(xrange,yrange) > 5E5: # 'i' = intermeditate
        map.resolution = 'i'
    elif max(xrange,yrange) < 5E5 and max(xrange,yrange) > 1E5: # 'h' = high
        map.resolution = 'h'
    elif max(xrange,yrange) < 1E5: # 'f' = full
        map.resolution = 'f'
    else: # 'c' = coarse
        map.resolution = 'c'

    print(map.resolution)
    map.drawcoastlines(linewidth=0.50)
    map.fillcontinents()
    map.drawmapboundary()

ax.callbacks.connect('xlim_changed', on_lims_change)

plt.show()

Answer 1

我发现最好的方法是打电话

zoomcall = ax.callbacks.connect('ylim_changed', onzoom)
ax.patches.clear()
ax.collections.clear()
ax.callbacks.disconnect(zoomcall)

为了（1）建立回调，（2）清除旧地图和（3）清除回调。这是作为易于使用的新类的一部分完成的。

这是代码大纲：

class ZoomPlot():

    def __init__(self, pnts):
        self.fig = plt.figure(figsize=(15,9))
        self.ax = self.fig.add_subplot(111)

        self.bnds = self.bnds_strt = [-58, 80, -180, 180]
        self.resolution = 'c'

        self.plot_map()

    def plot_map(self):
        self.map = Basemap(projection='merc',llcrnrlat=self.bnds[0],urcrnrlat=self.bnds[1],
                      llcrnrlon=self.bnds[2],urcrnrlon=self.bnds[3],resolution=self.resolution)

        self.map.drawcoastlines()
        self.map.drawmapboundary(fill_color='cornflowerblue')
        self.map.fillcontinents(color='lightgreen', lake_color='aqua')
        self.map.drawcountries()
        self.map.drawstates()

        self.plot_points()

        self.fig.canvas.draw()

        self.zoomcall = self.ax.callbacks.connect('ylim_changed', self.onzoom)

    def onzoom(self, axes):
        #print('zoom triggered')
        self.ax.patches.clear()
        self.ax.collections.clear()
        self.ax.callbacks.disconnect(self.zoomcall)

        x1, y1 = self.map(self.ax.get_xlim()[0], self.ax.get_ylim()[0], inverse = True)
        x2, y2 = self.map(self.ax.get_xlim()[1], self.ax.get_ylim()[1], inverse = True)
        self.bnds = [y1, y2, x1, x2]

        # reset zoom to home (workaround for unidentified error when you press the home button)
        if any([a/b > 1 for a,b in zip(self.bnds,self.bnds_strt)]):
            self.bnds = self.bnds_strt # reset map boundaryies
            self.ax.lines.clear() # reset points
            self.ab.set_visible(False) # hide picture if visible

        # change map resolution based on zoom level
        zoom_set = max(abs(self.bnds[0]-self.bnds[1]),abs(self.bnds[2]-self.bnds[3]))
        if zoom_set < 30 and zoom_set >= 3:
            self.resolution = 'l'
            #print('   --- low resolution')
        elif zoom_set < 3:
            self.resolution = 'i'
            #print('   --- intermeditate resolution')
        else:
            self.resolution = 'c'
            #print('   --- coarse resolution')

        self.plot_map()