An Introduction to Cairocffi: Advanced Canvas Manipulations and Graphics

Cairocffi is a brilliant Python library for 2D graphics that acts as a CFFI-based drop-in replacement for Pycairo. It allows developers to create vector graphics using the Cairo graphics library with a focus on advanced canvas manipulations and rendering stunning visuals.

Getting Started with Cairocffi

To start using Cairocffi, install it via pip:

$ pip install cairocffi

Basic Drawing Operations

Creating a Surface and a Context

import cairocffi as cairo

# Create a new surface of size 400x400
surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, 400, 400)
context = cairo.Context(surface)

Drawing Shapes

To draw basic shapes like rectangles, lines, and circles:

context.rectangle(50, 50, 300, 300)  # Rectangle(x, y, width, height)
context.set_source_rgb(0, 0, 1)      # Set color to blue
context.fill()                       # Fill the rectangle with blue color

context.move_to(50, 350)
context.line_to(350, 50)
context.set_source_rgb(1, 0, 0)
context.set_line_width(5)
context.stroke()                     # Draw the line with red color

Advanced Drawing Techniques

Gradients

gradient = cairo.LinearGradient(0, 0, 400, 0)
gradient.add_color_stop_rgb(0, 1, 0, 0)  # Red at the start
gradient.add_color_stop_rgb(1, 0, 0, 1)  # Blue at the end
context.rectangle(50, 50, 300, 300)
context.set_source(gradient)
context.fill()

Text Rendering

context.select_font_face("Sans", cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_NORMAL)
context.set_font_size(40)
context.move_to(50, 200)
context.set_source_rgb(0, 1, 0)
context.show_text("Hello World")

Embedding Images

image_surface = cairo.ImageSurface.create_from_png("path/to/image.png")
context.set_source_surface(image_surface, 100, 100)
context.paint()  # Draw the image on the context

Application Example

Here’s a simple example application using introduced APIs to create a complex scene:

import cairocffi as cairo

def draw_scene():
    surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, 800, 600)
    context = cairo.Context(surface)

    # Background gradient
    gradient = cairo.LinearGradient(0, 0, 800, 0)
    gradient.add_color_stop_rgb(0, 0.5, 0.5, 0.5)
    gradient.add_color_stop_rgb(1, 0.9, 0.9, 0.9)
    context.rectangle(0, 0, 800, 600)
    context.set_source(gradient)
    context.fill()
    
    # Drawing shapes
    context.rectangle(100, 100, 200, 200)
    context.set_source_rgb(1, 0, 0)
    context.fill()

    context.arc(500, 300, 100, 0, 2 * 3.14)
    context.set_source_rgb(0, 1, 0)
    context.fill()

    # Text
    context.select_font_face("Arial", cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_BOLD)
    context.set_font_size(50)
    context.move_to(150, 500)
    context.set_source_rgb(0, 0, 1)
    context.show_text("CairoCFFI Art")

    # Save the surface as an image file
    surface.write_to_png("output_image.png")

if __name__ == "__main__":
    draw_scene()

This example demonstrates how to combine shapes, gradients, text, and images into a complex visual output.

Happy coding with cairocffi!

Hash: d5e845e48f5f1788da2cc4e6d6e7ce9b7c496ab913bbaf547c911ea774c7e9b0