Convert Texts to Images with Python

Introduction

In this lab, we will learn how to use Python's Matplotlib library to convert texts to images. This is useful when we want to include text in an image or visualization, or when we want to create images of text for use in machine learning or computer vision applications.

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.

Import the necessary libraries

We will start by importing the necessary libraries, which include Matplotlib and BytesIO.

from io import BytesIO
import matplotlib.pyplot as plt
from matplotlib.figure import Figure
from matplotlib.transforms import IdentityTransform

Convert text to RGBA

To convert text to an image, we will draw it on an empty and transparent figure, save the figure to a temporary buffer, and then load the buffer using plt.imread.

def text_to_rgba(s, *, dpi, **kwargs):
    fig = Figure(facecolor="none")
    fig.text(0, 0, s, **kwargs)
    with BytesIO() as buf:
        fig.savefig(buf, dpi=dpi, format="png", bbox_inches="tight", pad_inches=0)
        buf.seek(0)
        rgba = plt.imread(buf)
    return rgba

Draw text images to a figure

Once we have converted the text to an RGBA image, we can draw it to a figure using .Figure.figimage.

fig = plt.figure()
rgba1 = text_to_rgba(r"IQ: $\sigma_i=15$", color="blue", fontsize=20, dpi=200)
rgba2 = text_to_rgba(r"some other string", color="red", fontsize=20, dpi=200)

fig.figimage(rgba1, 100, 50)
fig.figimage(rgba2, 100, 150)

plt.show()

Draw texts to a figure with positioning in pixel coordinates

Alternatively, we can directly draw text to a figure with positioning in pixel coordinates by using .Figure.text together with .transforms.IdentityTransform.

fig.text(100, 250, r"IQ: $\sigma_i=15$", color="blue", fontsize=20, transform=IdentityTransform())
fig.text(100, 350, r"some other string", color="red", fontsize=20, transform=IdentityTransform())

plt.show()

Summary

In this lab, we learned how to use Matplotlib to convert texts to images. We used the text_to_rgba function to convert text to an RGBA image, and then used .Figure.figimage and .Figure.text to draw the text image or text to a figure. This is useful for creating images of text for use in machine learning or computer vision applications, or for including text in visualizations.

Convert Texts to Images