Simple vector graphics in Python
Gizeh - Cairo for tourists
Gizeh is a Python library for vector graphics:
# 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
You can see examples of Gizeh in action (combined with MoviePy to make animations) in this blog post.
Gizeh is written on top of the module cairocffi, which is a Python binding of the popular C library Cairo. Cairo is powerful, but difficult to learn and use. Gizeh implements a few classes on top of Cairo that make it more intuitive.
Gizeh should work on any platform and with python 2 and 3.
To use Gizeh you must first install Cairo on your computer (see their website).
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. If you have trouble with the installation, head to the last section of this README for troubleshooting. If it doesn’t help, you can ask for help on Github.
Installation from the sources: Gizeh can be installed by unzipping the source code in some directory and using this command in the same directory:
(sudo) python setup.py install
Installation with pip: Alternatively, you can install Gizeh directly from the Python Package Index with this command:
(sudo) pip install gizeh
This method may fail if ez_setup is not installed on your computer. In this case install ez_setup first, with
(sudo) pip install ez_setup
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.
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.write_to_png("circle.png")
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. At rendering time (in function surface.write_to_png) you can set the parameter y_origin to top (default) or bottom. If you leave it to top, (0,0) corresponds to the upper left corner of the final picture, and the bottom right corner has coordinates (width, height). If you choose y_origin=bottom, (0,0) will be at the bottom left of the picture (like in a standard plot) and (width, height) will be at the upper right corner.
- 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=(50,50), fill=(1,1,1)) rect = gizeh.rectangle(lx=60.3, ly=45, xy=(60,70), fill=(0,1,0), angle=Pi/8) sqr = gizeh.square(l=20, stroke=(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, fill=(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=(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 color 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).
Any element can be transformed (translated, rotated or scaled). All transformations are outplace: they do not modify the original element, they create a modified version of it.
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
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.
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.
Sometimes the installation through pip fails because
Some people have had problems to install cairocffi, Here is how they solved their problem:
sudo apt-get install python-dev python-pip ffmpeg libffi-dev sudo pip install gizeh
pip install ez_setup brew install pkg-config libffi export PKG_CONFIG_PATH=/usr/local/Cellar/libffi/3.0.13/lib/pkgconfig/ # go to https://xquartz.macosforge.org and download and install XQuartz, # which is needed for cairo, then... brew install cairo pip install gizeh