gizeh 0.1.01

Simple vector graphics in Python

Python has a fast and powerful vector graphics library called PyCairo, but its is difficult to learn and use. Gizeh implements a few classes on top of Cairo that make it easier to use:

# Let's draw a red circle !
import gizeh
surface = gizeh.Surface(width=320, height=260) # in pixels
circle = gizeh.circle(r=30, xy= [40,40], fill_color=(1,1,1))
circle.draw(surface)
surface.write_to_png("circle.png")

Gizeh is an open-source software written by Zulko and released under the MIT licence. Everyone is welcome to contribute ! Keep in mind that it is a very basic package, by someone who hasn’t read half of the Cairo manual.

Installation

gizeh can be installed by unzipping the source code in one directory and using this command:

(sudo) python setup.py install

You can also install it directly from the Python Package Index with this command:

(sudo) pip install gizeh

Gizeh depends on the Python packages PyCairo and Numpy. They will both be automatically installed (if they aren’t already) during the installation of Gizeh.

User Guide

Surfaces

A Surface is a rectangle of fixed dimensions (in pixels), on which you will draw elements, and that you can save as an image:

import gizeh

# initialize surface
surface = gizeh.Surface(width=320, height=260) # in pixels

# Now make a shape and draw it on the surface
circle = gizeh.circle(r=30, xy= [40,40], fill_color=(1,1,1))
circle.draw(surface)

# No export the surface
surface.write_to_png("circle.png") # saves as an image.
surface.get_npimage() # returns a (width x height x 3) numpy array

Elements

Basic elements are circles, rectangles, etc., that you can draw on a surface using my_element.draw(surface). You can specify the properties and coordinates of these elements at creation time:

• xy : coordinates of the center of the object. (0,0), which is the defaut, corresponds to the upper left corner of the final picture.

• angle : angle (in radians) of the rotation of the element around it its center xy.

• fill_color : the color with which the element will be filled. Default (None) is no fill. The colors are represented by tuples (a,b,c) (for (red, green, blue) where a,b,c are comprised between 0 and 1. For instance (0,0,0) is black, (1,1,1) is white.

• stroke_color : the color of the element’s contour.

• stroke_width : the width (in pixels) of the element’s contour. Default is 0 (no stroke).

Examples:

Pi = 3.14
circ = gizeh.circle(r=30, xy=30, fill_color=(1,1,1))
rect = gizeh.rectangle(lx=60.3, ly=45, xy=30, fill_color=(0,1,0), angle=Pi/8)
sqr = gizeh.square(l=20, stroke_color=(1,1,1), stroke_width= 1.5)
arc = gizeh.arc(r=20, a1=Pi/4, a2=3*Pi/4, fill_color=(1,1,1))

Transformations

Any element can be tranformed (translated, rotated or scaled). All transformations are outplace: they do not modify the original element, they create a modified version of it.

Examples:

square_1 = gizeh.square(l=20, xy = [30,35], fill_color=(1,0,0))
square_2 = square_1.rotate(Pi/8) # rotation around [0,0] by default
square_3 = square_2.rotate(Pi/4, center=[10,15]) # rotation around a center
square_4 = square_1.scale(2) # two times bigger
square_5 = square1.scale(sx=2, sy=3) # width times 2, height times 3
square_6 = square_1.scale(2, center=[30,30]) # zoom: scales around a center
square_7 = square_1.translate(xy=[5,15]) # translation

Groups

A Group is a collection of elements which will be transformed and drawn together. The elements can be a basic element (square, circle…) or even groups.

Examples:

square = gizeh.square(l=20, fill_color=(1,0,0), xy=(40,40))
circle = gizeh.circle(r=20, fill_color=(1,2,0), xy=(50,30))
group_1 = gizeh.Group([square, circle])
group_2 = group.translate(xy=[30,30]).rotate(Pi/4)
group_3 = gizeh.Group([circle, group_1])

surface = gizeh.Surface(width=300,height=200)
group.draw(surface)
group_1.draw(surface)
group_2.draw(surface)
group_3.draw(surface)
surface.write_to_png("my_masterwork.png")

That’s all folks !

To go further, see the examples in the examples folder or (wishful thinking) on the Web.