Question

我需要创建一个更新matplotlib图形的滑块。到目前为止，我已经有了main.py：

from kivy.app import App
from kivy.properties import ObjectProperty
from kivy.uix.boxlayout import BoxLayout
import numpy as np
import matplotlib.pyplot as plt
from kivy.garden.matplotlib.backend_kivyagg import FigureCanvasKivyAgg

class Container(BoxLayout):
    display = ObjectProperty()
    def __init__(self, *args, **kwargs):
        global canvas
        super(Container, self).__init__(**kwargs)
        lum_img = np.random.rand(10,10)
        plt.imshow(lum_img, cmap="gray")
        plt.colorbar() 
        canvas = FigureCanvasKivyAgg(plt.gcf())
        self.ids.box_display.add_widget(canvas)
        canvas.draw()

    def add_one(self, value):
        lum_img = np.random.rand(10,10)
        plt.imshow(lum_img, cmap="gray")
        plt.colorbar() 
        canvas.draw()

        self.display.text = str(round(value,2))



class MainApp(App):
    def build(self):
        self.title = 'Image and slider app'

        return Container()


if __name__ == "__main__":
    app = MainApp()
    app.run()

main.kv：

<Container>:
    display: display
    id: main_display
    orientation: "vertical"

    BoxLayout:
        id: box_display
        orientation: "vertical"


        Slider:
            id: slider_image
            min: 0
            max: 1
            value: 0.5
            on_value: root.add_one(value = slider_image.value)

    Label:
        id: display
        font_size: dp(50)
        text: '0'

该行为不符合预期，它只是移动图像而不是更新图像画布！我认为错误是将画布声明为全局变量，但不执行此操作我不知道如何更新它。

有什么主意吗？

Answer 1

您的代码实际上是在创建新图，但它们的位置不正确且彼此重叠。解决该问题的一种方法是使用plt.subplot()。这需要预先知道要添加多少个子图。这是使用此方法的代码的修改版本（为方便起见，我将.kv作为字符串包括在内）

from kivy.app import App
from kivy.lang import Builder
from kivy.properties import ObjectProperty
from kivy.uix.boxlayout import BoxLayout
import numpy as np
import matplotlib.pyplot as plt
from kivy.garden.matplotlib.backend_kivyagg import FigureCanvasKivyAgg

Builder.load_string('''
<Container>:
    display: display
    id: main_display
    orientation: "vertical"

    BoxLayout:
        id: box_display
        orientation: "vertical"


        Slider:
            id: slider_image
            min: 0
            max: 1
            value: 0.0
            on_value: root.add_one(value = slider_image.value)

    Label:
        id: display
        font_size: dp(50)
        text: '0'
''')

class Container(BoxLayout):
    display = ObjectProperty()
    def __init__(self, *args, **kwargs):
        global canvas
        super(Container, self).__init__(**kwargs)
        self.index = 1    # index of the current plot
        self.max_plots = 5     # maximum number of subplots
        self.old_slider_value = 0.0   # starting value of the slider
        lum_img = np.random.rand(10,10)
        plt.subplot(1, self.max_plots, self.index)     # create the first subplot
        plt.imshow(lum_img, cmap="gray")
        plt.colorbar()
        canvas = FigureCanvasKivyAgg(plt.gcf())
        self.ids.box_display.add_widget(canvas)
        canvas.draw()

    def add_one(self, value):
        # only make a new subplot if the slider has moved at least 0.2
        if (value - self.old_slider_value) > 1.0/self.max_plots and self.index < self.max_plots:
            self.old_slider_value = value
            self.index += 1
            plt.subplot(1, self.max_plots, self.index)     # make new subplot
            lum_img = np.random.rand(10,10)
            plt.imshow(lum_img, cmap="gray")
            plt.colorbar()
            plt.tight_layout()     # arrange the subplots a bit to eliminate overlaps
            canvas.draw()

        self.display.text = str(round(value,2))



class MainApp(App):
    def build(self):
        self.title = 'Image and slider app'

        return Container()


if __name__ == "__main__":
    app = MainApp()
    app.run()

Answer 2

误解了您想要的内容（我的错误）。如果您不想创建新图，而只是更新现有图，则只需执行plt.clf()方法中对add_one()的调用即可，然后再进行其他图。这样可以清除当前图形，并允许您将其替换为新图形。

Kivy：使用滑块更新Matplotlib画布

2 个答案: