Re: [Matplotlib-users] Simple scatter plot over an image

[Jake E. <jak...@on...>]

The python imaging library is pretty good for this kind of thing.
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http://www.pythonware.com/library/pil/handbook/
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Here's an (untested) example. Hope it helps.
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Jake
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#!/usr/bin/env python
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from pylab import scatter, save
import Image
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#get the background image, and find out how big it is
im_bg =3D Image.open("background.png")
bg_width, bg_height =3D im.size
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#make a white canvas on which to paste the background image and the
scatter plot
#this will allow you to, say, have the x- and y-axis values fall outside
of the background image's limits
im_canvas =3D Image.new("RGBA", (bg_width+60, bg_height+60), (255, 255,
255, 0))
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#create the scatter plot from x and y data with matplotlib
scatter(x, y, s=3Dsizes, alpha=3D0.75)
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#save the scatter plot, and then retrieve it for use in PIL, convert to
RGBA so that alpha levels will work
#there is probably a better way to do this with gcf() or gci()...
savefig("scatter_plot.png")
im_scatter =3D Image.open("scatter_plot.png").convert("RGBA")
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#resize the scatter image to make it fit nice
im_scatter.resize((bg_width+10, bg_height+10))
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#bring all of the images together by pasting them onto the white canvas,
use the overlayed image as the mask (third element)
im_canvas.paste(im_bg, (30, 30), im_bg)                   #play around
with the paste locations (30, 30)
im_canvas.paste(im_scatter, (10, 30), im_scatter)      #these won't be
perfect the first time (10, 30)
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#save it
im_canvas.save("combo_image.png")
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________________________________

From: __ [mailto:red...@gm...]=20
Sent: Sunday, June 10, 2007 5:22 PM
To: mat...@li...
Subject: [Matplotlib-users] Simple scatter plot over an image


Hello,=20

I'm trying to plot a simple list of x/y coords over an image (.png). I
can show the image, or plot the data, but cannot find a way to layer one
over the other. I would greatly appreciate someone pointing me in the
right direction. Thanks.=20