Calculating Additional Space Caused by Text Descenders in Pillow

What will you learn?

In this tutorial, you will delve into the realm of text rendering using Pillow, the Python Imaging Library. You will master the art of calculating extra space introduced by descenders in text to enhance your image processing projects.

Introduction to the Problem and Solution

When incorporating text into images dynamically, understanding the complete space occupied by text is crucial. This includes accounting for descenders – parts of characters that extend below the baseline (like “y”, “g”, “p”, etc.). By accurately measuring this additional space, you can refine your layout for a more professional appearance.

To tackle this challenge effectively, we will harness the power of Pillow to precisely determine text size while considering descenders. We will guide you through setting up your environment, grasping fundamental Pillow operations, and calculating and visualizing the extra space caused by descenders. By the end of this tutorial, you will possess a reliable method to manage text dimensions proficiently in your image-processing endeavors.


from PIL import ImageFont, ImageDraw, Image

# Load or create an image
image ="RGB", (200, 100), color="white")
draw = ImageDraw.Draw(image)

# Specify font and text
font_path = "/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf"
font_size = 40
font = ImageFont.truetype(font_path, font_size)
text = "gjpqy"

# Calculate text size including descender space
text_width, text_height = draw.textsize(text=text.upper(), font=font)
ascendents_and_descendents_bounds = font.getmask(text).getbbox()
actual_text_height_with_descender_space= ascendents_and_descendents_bounds[3] - ascendents_and_descendents_bounds[1]

# Display results
print(f"Calculated Text Height: {text_height}")
print(f"Actual Text Height Considering Descenders: {actual_text_height_with_descender_space}")

# Copyright PHD


The provided code snippet showcases how to determine the true height of text while accounting for descenders that often go unnoticed during space estimations for textual content in images. Here’s a breakdown: – Pillow Setup: Begin by importing essential classes from PIL (Python Imaging Library) and creating a blank white image canvas. – Text Configuration: Define desired font attributes and input sample text for dimension analysis. – Calculating Size: Utilize draw.textsize() initially but overcome its limitation by: – Employing font.getmask(text).getbbox() to retrieve a tuple representing the bounding box encompassing all painted pixels (including descenders). – Compute actual height as the disparity between lowest ([3]) and highest points ([1]) within these bounds.

This methodology ensures comprehensive consideration of all textual aspects for precise dimension computation.

  1. How do I install Pillow?

  2. To install Pillow, execute:

  3. pip install Pillow
  4. # Copyright PHD
  5. Can I use custom fonts with Pillow?

  6. Absolutely! Simply provide the correct path to a .ttf file using ImageFont.truetype.

  7. What is a descender?

  8. A descender refers to a portion of certain lowercase letters that extends below their baseline.

  9. Why is considering descendens important?

  10. Neglecting them may lead to inaccurate layout calculations resulting in truncated or excessively spaced texts.

  11. Does draw.textsize() always exclude descendens?

  12. Primarily yes; it calculates based on character heights without specific glyph details such as descendens.

  13. Is there any way to visualize these measurements?

  14. You can draw rectangles on your canvas using calculated dimensions as guides.

  15. Can I apply this technique for multiline texts?

  16. Yes, but it necessitates additional logic to manage line breaks and vertical spacing correctly.

  17. What file formats does PIL support?

  18. PIL supports major formats like JPEG PNG GIF TIFF BMP among others.

  19. Are there performance considerations with large texts/images?

  20. Processing time might increase with complexity; optimize by scaling down images or processing chunks separately where feasible.

  21. Can I use other libraries alongside PIL/Pillow?

  22. Certainly! Libraries like NumPy can facilitate advanced numerical operations.

  23. Do different fonts impact calculation accuracy?

  24. Yes, as each font possesses unique characteristics affecting overall dimensions especially concerning descendens.


Comprehending how elements like descenders influence overall dimensions proves vital across various domains from web development to data visualization. Armed with tools like Pillow and Python´┐Żs adaptability, detailed analysis adjustments become less daunting tasks. This empowers developers and designers alike to focus more on unleashing creativity rather than troubleshooting layout intricacies.

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