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

# Text alignment using text extent
We can use the text extents to align text. As an example, we will look at the ways to align text to the left, right, and center. Here is a function that displays a string that is left-aligned to the point `(x, y)`:

```python
def left_align(ctx, x, y, text):
    ctx.move_to(x, y)
    ctx.set_source_rgb(0, 0, 0)
    ctx.show_text(text)
```
This is fairly standard. It sets the current point to `(x, y)`, sets the color to black, and then shows the text using the current font and size. The text is automatically left-aligned because that is Pycairo’s default alignment setting.

Here is the code to right-align text to the point `(x, y)`:

```python
def right_align(ctx, x, y, text):
    xbearing, ybearing, width, height, dx, dy = ctx.text_extents(text) 
    ctx.move_to(x - width, y)
    ctx.set_source_rgb(0, 0, 0)
    ctx.show_text(text)
```
In this case, we make an extra call to the `text_extents` function. The only value we are interested in is the width value.

We set the current point to `(x - width, y)`. This means that the starting point of any text string depends on its width. It will always start at x-width, which means that the string will always end at `(x, y)`.

> **Note**: We only use the `width` value in this calculation. This assumes that the `xbearing` is zero (or negligible, at the very least). This is true of Latin characters, but might not necessarily be true of other writing systems.

We can also center-align text by setting the current point to `(x - width/2, y)`:

```python
def center_align(ctx, x, y, text):
    xbearing, ybearing, width, height, dx, dy = ctx.text_extents(text)
    ctx.move_to(x - width/2, y)
    ctx.set_source_rgb(0, 0, 0)
    ctx.show_text(text)
```
Here is an example of these three functions in action:


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 Alignment

Text alignment using text extent