How do you draw transparent polygons with Python?

python-imaging-library polygon alpha
carrier picture carrier · Dec 11, 2008 · Viewed 28.2k times · Source

I'm using PIL (Python Imaging Library). I'd like to draw transparent polygons. It seems that specifying a fill color that includes alpha level does not work. Are their workarounds?

If it can't be done using PIL I'm willing to use something else.

If there is more than one solution, then performance should be factored in. The drawing needs to be as fast as possible.

Answer

Matt picture Matt · Feb 14, 2014

This is for Pillow, a more maintained fork of PIL. http://pillow.readthedocs.org/

If you want to draw polygons that are transparent, relative to each other, the base Image has to be of type RGB, not RGBA, and the ImageDraw has to be of type RGBA. Example:

from PIL import Image, ImageDraw

img = Image.new('RGB', (100, 100))
drw = ImageDraw.Draw(img, 'RGBA')
drw.polygon([(50, 0), (100, 100), (0, 100)], (255, 0, 0, 125))
drw.polygon([(50,100), (100, 0), (0, 0)], (0, 255, 0, 125))
del drw

img.save('out.png', 'PNG')

This will draw two triangles overlapping with their two colors blending. This a lot faster than having to composite multiple 'layers' for each polygon.

Related questions

Installing PIL with pip

I am trying to install PIL (the Python Imaging Library) using the command: sudo pip install pil but I get the following message: Downloading/unpacking PIL You are installing a potentially insecure and unverifiable file. Future versions of pip will …

Read More
How do I resize an image using PIL and maintain its aspect ratio?

Is there an obvious way to do this that I'm missing? I'm just trying to make thumbnails.

Read More
ImportError: No module named PIL

I use this command in the shell to install PIL: easy_install PIL then I run python and type this: import PIL. But I get this error: Traceback (most recent call last): File "<console>", line 1, in <module&…

Read More