多边形选择器演示

显示如何以交互方式选择多边形的索引。

多边形选择器演示

输出：

  1. Select points in the figure by enclosing them within a polygon.
  2. Press the 'esc' key to start a new polygon.
  3. Try holding the 'shift' key to move all of the vertices.
  4. Try holding the 'ctrl' key to move a single vertex.
  6. Selected points:
  7. []
  1. import numpy as np
  3. from matplotlib.widgets import PolygonSelector
  4. from matplotlib.path import Path
  7. class SelectFromCollection(object):
  8.     """Select indices from a matplotlib collection using `PolygonSelector`.
  10.     Selected indices are saved in the `ind` attribute. This tool fades out the
  11.     points that are not part of the selection (i.e., reduces their alpha
  12.     values). If your collection has alpha < 1, this tool will permanently
  13.     alter the alpha values.
  15.     Note that this tool selects collection objects based on their *origins*
  16.     (i.e., `offsets`).
  18.     Parameters
  19.     ----------
  20.     ax : :class:`~matplotlib.axes.Axes`
  21.         Axes to interact with.
  23.     collection : :class:`matplotlib.collections.Collection` subclass
  24.         Collection you want to select from.
  26.     alpha_other : 0 <= float <= 1
  27.         To highlight a selection, this tool sets all selected points to an
  28.         alpha value of 1 and non-selected points to `alpha_other`.
  29.     """
  31.     def __init__(self, ax, collection, alpha_other=0.3):
  32.         self.canvas = ax.figure.canvas
  33.         self.collection = collection
  34.         self.alpha_other = alpha_other
  36.         self.xys = collection.get_offsets()
  37.         self.Npts = len(self.xys)
  39.         # Ensure that we have separate colors for each object
  40.         self.fc = collection.get_facecolors()
  41.         if len(self.fc) == 0:
  42.             raise ValueError('Collection must have a facecolor')
  43.         elif len(self.fc) == 1:
  44.             self.fc = np.tile(self.fc, (self.Npts, 1))
  46.         self.poly = PolygonSelector(ax, self.onselect)
  47.         self.ind = []
  49.     def onselect(self, verts):
  50.         path = Path(verts)
  51.         self.ind = np.nonzero(path.contains_points(self.xys))[0]
  52.         self.fc[:, -1] = self.alpha_other
  53.         self.fc[self.ind, -1] = 1
  54.         self.collection.set_facecolors(self.fc)
  55.         self.canvas.draw_idle()
  57.     def disconnect(self):
  58.         self.poly.disconnect_events()
  59.         self.fc[:, -1] = 1
  60.         self.collection.set_facecolors(self.fc)
  61.         self.canvas.draw_idle()
  64. if __name__ == '__main__':
  65.     import matplotlib.pyplot as plt
  67.     fig, ax = plt.subplots()
  68.     grid_size = 5
  69.     grid_x = np.tile(np.arange(grid_size), grid_size)
  70.     grid_y = np.repeat(np.arange(grid_size), grid_size)
  71.     pts = ax.scatter(grid_x, grid_y)
  73.     selector = SelectFromCollection(ax, pts)
  75.     print("Select points in the figure by enclosing them within a polygon.")
  76.     print("Press the 'esc' key to start a new polygon.")
  77.     print("Try holding the 'shift' key to move all of the vertices.")
  78.     print("Try holding the 'ctrl' key to move a single vertex.")
  80.     plt.show()
  82.     selector.disconnect()
  84.     # After figure is closed print the coordinates of the selected points
  85.     print('\nSelected points:')
  86.     print(selector.xys[selector.ind])

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