Gain insights into computer graphics with Python's Pycairo library. Learn about pixel vs. vector graphics, create complex shapes, work with transforms, text, gradients, and more for VR and game development.

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Pycairo

In this course, you will use Python’s Pycairo library to draw complex shapes. So if you have an appetite for virtual reality, or game development, then this course will serve you well.

You will start with basic concepts like: What is the difference between pixel and vector graphics? After that, you will learn to make basic drawings and then you will move on to complex shapes. Throughout, you will cover important concepts like transform and state, working with text, gradients, and a whole lot more.

By the time you finish this course, you will have a powerful new library at your disposal, and you’ll be able to construct beautiful graphics that users will love.

Computer Graphics in Python and Pycairo

# What is text?
At its most basic level, text is just a collection of shapes. Take a look at the huge text below:


Each letter is just a shape, created from straight lines and Bezier curves. Ultimately, Pycairo will draw each letter simply as a shape with no understanding of its meaning.

# How Pycairo handles text
Of course, text isn’t really just shapes. Those shapes have meaning. They are letters that combine to make words and sentences.

Trying to add text to our file by drawing the shape of each character would be ridiculously difficult and tedious. Pycairo handles text at a higher level. Normally, we specify the text as a text string, and then set the size and font that is required.

 We select a font to control the typeface that is used to display or print text. But, what exactly is a font? In simple terms, it is a file that defines the shapes of each letter, number, and symbol, in some defined character set and for a particular typeface.

When we add text in Pycairo, we use a Python string of characters. The font file contains information about the size of each character, and Pycairo uses this information to correctly position each character in the string. This is the code to draw a simple text string:


import cairo

# Set up surface
surface = cairo.ImageSurface(cairo.FORMAT_RGB24, 400, 400)
ctx = cairo.Context(surface)
ctx.set_source_rgb(0.8, 0.8, 0.8)
ctx.paint()

# Select font
ctx.select_font_face("Arial CE")
ctx.set_font_size(50)

# Add text
ctx.set_source_rgb(0, 0, 0)
ctx.move_to(100, 200)
ctx.show_text("text")

Here are the basic steps of the process:

1. Use `select_font_face` to choose the font for the text. This is exactly the same as choosing a font in a word processor or spreadsheet.
2. Use `set_font_size` to set the size. With the default scaling, this is the approximate character size in pixels.
3. Set the color to black in the usual way, with `set_sorce_rgb`.
4. Use the `move_to` function to set the current point. This will be the starting point of the text (the baseline position of the first character).
5. Finally, call the `show_text` function to draw the characters.

Notice that we only need to specify one position: `(100, 200)`. This is the position of the first “t” in the string. The remaining characters “e”, “x”, and “t” are positioned automatically, using character metrics supplied by the font.


Learn about the basics of the texts that are used in Pycairo.

Introduction

Introduction to Vector Graphics

Basic Drawing Operations

Paths and Complex Shapes

Computer Color

Transforms and State

Working with Text

Gradients and Image Fills

Clipping, Masking and Compositing

Surfaces and Output Formats

Integration with Other Libraries

Conclusion

Text Is Just Shapes

What is text?

How Pycairo handles text