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https://github.com/Zulko/gizeh

Simple Vector Graphics for Python
https://github.com/Zulko/gizeh

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Simple Vector Graphics for Python

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README 

        
.. image:: https://raw.githubusercontent.com/Zulko/gizeh/master/logo.jpeg

   :alt: [logo]

   :align: center



Gizeh - Cairo for tourists

===========================



Gizeh is a Python library for vector graphics:



.. code:: python



    # 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.



Installation

--------------



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



Contribute !

-------------



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 !



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:



.. code:: python



    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")



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. 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:



.. code:: python



    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.regular_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).



Transformations

~~~~~~~~~~~~~~~~



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.



Examples:



.. code:: python



    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:



.. code:: python



    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 the documentation

directly in the code.



Installation support

---------------------



Sometimes the installation through `pip` fails because



Some people have had problems to install ``cairocffi``, Here is how they solved

their problem:



On Debian/Ubuntu ::



    sudo apt-get install python-dev python-pip ffmpeg libffi-dev

    sudo pip install gizeh



On macOSX ::



    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



.. _Zulko : https://github.com/Zulko

.. _Github: https://github.com/Zulko/gizeh

.. _Cairo:  http://cairographics.org/