Mathtext Wx Sgskip

Introduction

This lab will guide you through creating a wxPython application that displays math text in a wx.Bitmap for display in various controls on wxPython. It uses the Matplotlib library to convert text to images and the wxPython library to display the images.

VM Tips

After the VM startup is done, click the top left corner to switch to the Notebook tab to access Jupyter Notebook for practice.

Sometimes, you may need to wait a few seconds for Jupyter Notebook to finish loading. The validation of operations cannot be automated because of limitations in Jupyter Notebook.

If you face issues during learning, feel free to ask Labby. Provide feedback after the session, and we will promptly resolve the problem for you.

Install Required Libraries

To complete this lab, you need to have the following libraries installed:

• wxPython
• Matplotlib

You can install these libraries using pip.

pip install wxPython
pip install matplotlib

Create a wxPython Application

Create a new Python file and import the required libraries.

import wx
import numpy as np
from io import BytesIO
from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg as FigureCanvas
from matplotlib.figure import Figure

Convert Mathtext to wx.Bitmap

Define a function that converts math text to a wx.Bitmap. This function uses Matplotlib to draw the text at position (0, 0) but then relies on facecolor="none" and bbox_inches="tight", pad_inches=0 to get a transparent mask that is then loaded into a wx.Bitmap.

def mathtext_to_wxbitmap(s):
    fig = Figure(facecolor="none")
    text_color = (
        np.array(wx.SystemSettings.GetColour(wx.SYS_COLOUR_WINDOWTEXT)) / 255)
    fig.text(0, 0, s, fontsize=10, color=text_color)
    buf = BytesIO()
    fig.savefig(buf, format="png", dpi=150, bbox_inches="tight", pad_inches=0)
    s = buf.getvalue()
    return wx.Bitmap.NewFromPNGData(s, len(s))

Define Functions

Define a list of functions that the application will display. Each function is defined by a math text and a lambda function that takes an input value and returns an output value.

functions = [
    (r'$\sin(2 \pi x)$', lambda x: np.sin(2*np.pi*x)),
    (r'$\frac{4}{3}\pi x^3$', lambda x: (4/3)*np.pi*x**3),
    (r'$\cos(2 \pi x)$', lambda x: np.cos(2*np.pi*x)),
    (r'$\log(x)$', lambda x: np.log(x))
]

Create a Canvas Frame

Create a new class that inherits from wx.Frame. This class creates a canvas that displays the selected function.

class CanvasFrame(wx.Frame):
    def __init__(self, parent, title):
        super().__init__(parent, -1, title, size=(550, 350))

        self.figure = Figure()
        self.axes = self.figure.add_subplot()

        self.canvas = FigureCanvas(self, -1, self.figure)

        self.change_plot(0)

        self.sizer = wx.BoxSizer(wx.VERTICAL)
        self.add_buttonbar()
        self.sizer.Add(self.canvas, 1, wx.LEFT | wx.TOP | wx.GROW)

        self.SetSizer(self.sizer)
        self.Fit()

Add a Button Bar

Add a button bar to the application that displays icons for each function. When a button is clicked, the application will display the corresponding function.

    def add_buttonbar(self):
        self.button_bar = wx.Panel(self)
        self.button_bar_sizer = wx.BoxSizer(wx.HORIZONTAL)
        self.sizer.Add(self.button_bar, 0, wx.LEFT | wx.TOP | wx.GROW)

        for i, (mt, func) in enumerate(functions):
            bm = mathtext_to_wxbitmap(mt)
            button = wx.BitmapButton(self.button_bar, 1000 + i, bm)
            self.button_bar_sizer.Add(button, 1, wx.GROW)
            self.Bind(wx.EVT_BUTTON, self.OnChangePlot, button)

        self.button_bar.SetSizer(self.button_bar_sizer)

Add a Toolbar

Add a toolbar to the application that allows the user to zoom in and out, pan, and save the plot as an image. This toolbar is added to the bottom of the frame.

    def add_toolbar(self):
        self.toolbar = NavigationToolbar2Wx(self.canvas)
        self.toolbar.Realize()
        self.sizer.Add(self.toolbar, 0, wx.LEFT | wx.EXPAND)
        self.toolbar.update()

Change the Plot

Define a function that changes the plot based on the selected function. This function takes a plot_number as input and changes the plot accordingly.

    def change_plot(self, plot_number):
        t = np.arange(1.0, 3.0, 0.01)
        s = functions[plot_number][1](t)
        self.axes.clear()
        self.axes.plot(t, s)
        self.canvas.draw()

Create the Application

Create a new class that inherits from wx.App. This class creates the frame and starts the event loop.

class MyApp(wx.App):
    def OnInit(self):
        frame = CanvasFrame(None, "wxPython mathtext demo app")
        self.SetTopWindow(frame)
        frame.Show(True)
        return True

Run the Application

Run the application by creating an instance of the MyApp class.

if __name__ == "__main__":
    app = MyApp()
    app.MainLoop()

Summary

In this lab, you learned how to create a wxPython application that displays math text in a wx.Bitmap. You used the Matplotlib library to convert text to images and the wxPython library to display the images. You also learned how to create a button bar and a toolbar in the application and how to change the plot based on the selected function.