Computer graphics in Python by Martin McBride_468 x 60.png

pycairo.tar.gz

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

## Translation
**Translation** shifts the entire coordinate system. It is useful if we want to draw a shape in a different position, but without changing the drawing code.

We use the `translate` method of the `Context` to perform a translation:
```
ctx.translate(200, 300)
```
This moves the entire user space 200 units to the right, and 300 units down, relative to device space. This means that the origin in user space, now, corresponds to the point `(200, 300)` in device space.
> **Note:** In simpler terms, if we draw something at point `(x, y)` in user space after translating it by `(200, 300)`, it will appear at point `(x+200, y+300)` in device space.

The diagram below shows the transformed user space. The portion of user space that maps onto the entire device space is shown, so that the red square appears in the same place in both the user and device space. But, if we look at the coordinates for user space we will see that they shifted relative to device space.

The device space is unchanged by the transformation. Notice that some of the user space coordinates are now negative, because of the translation. This is fine, because those coordinates map onto non-negative values in device space. We can see this in the illustration below:


# Translation
**Translation** shifts the entire coordinate system. It is useful if we want to draw a shape in a different position, but without changing the drawing code.

We use the `translate` method of the `Context` to perform a translation:
```
ctx.translate(200, 300)
```
This moves the entire user space 200 units to the right, and 300 units down, relative to device space. This means that the origin in user space, now, corresponds to the point `(200, 300)` in device space.
> **Note:** In simpler terms, if we draw something at point `(x, y)` in user space after translating it by `(200, 300)`, it will appear at point `(x+200, y+300)` in device space.

The diagram below shows the transformed user space. The portion of user space that maps onto the entire device space is shown, so that the red square appears in the same place in both the user and device space. But, if we look at the coordinates for user space we will see that they shifted relative to device space.

The device space is unchanged by the transformation. Notice that some of the user space coordinates are now negative, because of the translation. This is fine, because those coordinates map onto non-negative values in device space. We can see this in the illustration below:


Learn about the translation method 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

Translation

Translation