Question

我正在帮助配置服务器端on_change事件以在绘图缩放时触发。我有一个大的2D数据阵列（5000，> 1000000），我希望将其视为使用散景的图像。因此，我将数据（skimage.transform.resize）的大小调整为散景图的宽度和高度。我试图使用on_change函数在绘图缩放，平移或重置时调用调整大小。我附加了一个回调函数x_range和y_ranges来触发开始和结束更改。但是这（可以理解）导致在每个缩放事件上触发调整大小回调4次。能够并且希望能够在范围变化的任何子集上触发调整大小事件（例如，缩放可能不会改变y_range.end），因此我不能简单地等待计算所有on_change事件。

示例代码：

import bokeh.plotting as bk
from bokeh.application.handlers import FunctionHandler
from bokeh.application import Application
from bokeh.models import LinearColorMapper, ColumnDataSource

from skimage.transform import resize

import numpy as np

import xarray as xa

bk.output_notebook()

# Create a simple array image - basically lifted from https://bokeh.pydata.org/en/latest/docs/gallery/image.html
N = 5000
x = np.linspace(0, 10*np.pi, N)
y = np.linspace(0, 10*np.pi, N)
xx, yy = np.meshgrid(x, y)
d = np.sin(xx)*np.cos(yy)

# Using xarray as this is the array handling object of choice in production code
array = xa.DataArray(data = d, coords = (x, y), dims = ('x', 'y'))

class Plot():

    def __init__(self, array, width = 800, height = 800):
        # Probably unecessary, but done for syntactic familiarity
        self.tla = array.to_pandas()

        xrange = self.tla.index
        yrange = self.tla.columns

        # Configure plot object
        self.p = bk.figure(height = height, width = width, 
                           x_range = (xrange.min(), xrange.max()),
                           y_range = (yrange.max(), yrange.min()))

        # Create ColoumnDataSource object with the resized input array, no arguments passed to
        # simplify its use during callback
        self.source = ColumnDataSource(data = {'image': [self.resize()]})

        # Colormapper for image and colorbar control
        self.color_mapper = LinearColorMapper(palette="Viridis256", low=-1, high=1)

        # Create image
        self.p.image('image', source = self.source, color_mapper=self.color_mapper,
                   dh=yrange.max() - yrange.min(), dw=xrange.max() - xrange.min(), x = xrange.min(), y=yrange.max())

        # Add callback to x_range and y_range
        self.p.x_range.on_change('end', self.callback)
        self.p.x_range.on_change('start', self.callback)
        self.p.y_range.on_change('end', self.callback)
        self.p.y_range.on_change('start', self.callback)


    def resize(self):
        # Slice tla frame by x and y range bounds and then resize to fit plot height and width
        return resize(self.tla.loc[self.p.x_range.start:self.p.x_range.end,
                                   self.p.y_range.end:self.p.y_range.start].as_matrix(),
                      [self.p.plot_width, self.p.plot_height], 
                      preserve_range = True, mode = 'reflect')

    def modify_doc(self, doc):
        # Add plot to document
        doc.add_root(self.p)

    def callback(self, attr, start, end):

        # Call resize
        data = ColumnDataSource(data = {'image': [self.resize()]}).data
        # Re-assign computed data to ColumnDataSource object
        self.source.data = data
        print("Callback calculated @ {0}:{1}, {2}:{3}".format(self.p.x_range.start, self.p.x_range.end, 
                                                    self.p.y_range.start, self.p.y_range.end))


# Create Plot
plot = Plot(array)

handler = FunctionHandler(plot.modify_doc)
app = Application(handler)

show(app)

我还考虑在绘图对象本身添加on_event更改，并向工具添加on_change回调，但似乎无法为这两个对象找到合适的触发器。

非常感谢任何帮助或建议！

Answer 1

在Bokeh的最新版本中，这些是事件：

https://docs.bokeh.org/en/latest/docs/reference/events.html

您将使用.on_event为它们注册回调。

Bokeh - 从BoxZoomTool / ResetTool触发on_change回调

1 个答案: