gizeh 0.1.04

Simple vector graphics in Python

Gizeh is a Python library for vector graphics written on top of cairocffi, which is a binding of the popular C library Cairo. Cairo is a powerful, but it is difficult to learn and use. Gizeh implements a few classes on top of Cairo that make it more intuitive:

# 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=(1,0,0))
circle.draw(surface) # draw the circle on the surface
surface.write_to_png("circle.png") # export the surface as a PNG

Gizeh is an open-source software written by Zulko and released under the MIT licence. The project is hosted on Github. Everyone is welcome to contribute !

Installation

Gizeh should work on any platform and with python 2 and 3. If you have difficulties installing it, you can ask for help on Github.

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 cairocffi and Numpy. They will both be automatically installed (if they aren’t already) during the installation of Gizeh.

User Guide

This guide, along with the examples in the gizeh/examples folder, should give you everything you need to get started. To go further, read the function docstrings.

Surfaces

A Surface is a rectangle of fixed dimensions (in pixels), on which you will draw elements, and that you can save or export 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=(1,1,1))
circle.draw(surface)

# Now export the surface
surface.get_npimage() # returns a (width x height x 3) numpy array
surface.scipy_imsave("circle.png") # requires scipy.
surface.write_to_png("circle.png") # doesn't require scipy, but image is flipped

Elements

Basic elements are circles, rectangles, lines, texts, 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 bottom left corner of the final picture.

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

• fill : what will fill the element (default is no fill). Can be a color (R,G,B), a color gradient, an image, etc. See section below.

• stroke : What will fill the element’s contour. Same rules as for fill.

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

Examples of elements:

Pi = 3.14
circ = gizeh.circle(r=30, xy=30, fill=(1,1,1))
rect = gizeh.rectangle(lx=60.3, ly=45, xy=30, fill=(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=(1,1,1))
text = gizeh.text("Hello world", fontfamily="Impact",  fontsize=40,
                  fontcolor=(1,1,1), xy=(100,100), angle=Pi/12)
polygon = gizeh.polygon(r=40, n=5, angle=np.pi/4, xy=[40,50], fill=(1,0,1))
line = gizeh.polyline(points=[(0,0), (20,30), (40,40), (0,10)], stroke_width=3,
                     stroke_color=(1,0,0), fill=(0,1,0))

Fill and stroke

When you make a shape, the fill and stroke parameters can be one of the following:

• A RGB color of the form (r,g,b) where each element is comprised between 0 and 1 (1 is 100%).

• A RGBA colot of the form (r,g,b,a), where a is comprised between 0 (totally transparent) and 1 (totally opaque).

• A gizeh.ColorGradient (see the docstring).

• A gizeh.ImagePattern, i.e. an image (see the docstring).

• A numpy array representing a RGB or RGBA image (not implemented yet).

• A PNG image file (not implemented yet).

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=(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=(1,0,0), xy=(40,40))
circle = gizeh.circle(r=20, fill=(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 !

That’s about all there is to know. To go further, see the examples in the examples folder or (wishful thinking) on the Web.