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

# RecordingSurface

A recording surface records drawing operations, which can later be played back to a normal surface. Here is an example of this:

import cairo 

#  Recorded page
rec_surface = cairo.RecordingSurface(cairo.Content.COLOR, None)
ctx=cairo.Context(rec_surface)
ctx.set_source_rgb(1, 1, 1)
ctx.paint()
ctx.rectangle(100, 100, 200, 200)
ctx.set_source_rgb(1, 0, 0)
ctx.fill()

# Page 1

surface = cairo.ImageSurface(cairo.FORMAT_RGB24, 600, 400)
ctx=cairo.Context(surface)

ctx.set_source_surface(rec_surface)
ctx.paint()

ctx.set_source_rgb(0, 0, 0)
ctx.move_to(500, 350)
ctx.set_font_size(20)
ctx.show_text('Page1')
surface.write_to_png('output/page1.png')

#  Page 2
surface = cairo.ImageSurface(cairo.FORMAT_RGB24, 600, 400)
ctx=cairo.Context(surface)

ctx.set_source_surface(rec_surface)
ctx.paint()

ctx.set_source_rgb(0, 0, 0)
ctx.move_to(500, 350)
ctx.set_font_size(20)
ctx.show_text('Page2')
surface.write_to_png('output/page2.png')

First, we create a `RecordingSurface`. This takes two parameters:

- `content` defines the type of content we want to record. This is set by a `cairo.Content` value of `COLOR`, `ALPHA`, or `COLOR_ALPHA` (to record color and alpha information)

- `rectangle` defines the area to record. Neither can be used to record all operations without bounds

Then, we then create a context and draw onto it in the usual way. We draw a red square on a white background. The drawing operations are recorded by the surface, ready to be played back later.

In the `Page 1` section, we create an `ImageSurface`. We can play back the recorded surface with this code:

```
ctx.set_source_surface(rec_surface)
ctx.paint()
```
This performs the recorded operations; it sets the background white and draws the red square on the `surface`. We continue to add some text to the `surface` in the usual way and save the result as `page1.png`.

Then, we repeat this process on a new `ImageSurface` to create another image: `page2.png`. The recording surface can be reused each time.

Recording surfaces are useful for content that will be repeated across multiple pages. This includes things that appear on every page, such as a company logo, or a watermark.



Learn about the uses of surfaces that are not used to create output.

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

Other Surfaces

RecordingSurface