Revision: 7582
http://matplotlib.svn.sourceforge.net/matplotlib/?rev=7582&view=rev
Author: jdh2358
Date: 2009-08-29 16:35:35 +0000 (Sat, 29 Aug 2009)
Log Message:
-----------
added Michael Sarahan's image tutorial from the scipy mpl sprint
Modified Paths:
--------------
branches/v0_99_maint/doc/_templates/indexsidebar.html
branches/v0_99_maint/doc/_templates/layout.html
branches/v0_99_maint/doc/devel/coding_guide.rst
branches/v0_99_maint/doc/users/index.rst
branches/v0_99_maint/doc/users/transforms_tutorial.rst
branches/v0_99_maint/doc/users/whats_new.rst
Added Paths:
-----------
branches/v0_99_maint/doc/_static/stinkbug.png
branches/v0_99_maint/doc/users/image_tutorial.rst
Added: branches/v0_99_maint/doc/_static/stinkbug.png
===================================================================
(Binary files differ)
Property changes on: branches/v0_99_maint/doc/_static/stinkbug.png
___________________________________________________________________
Added: svn:mime-type
+ application/octet-stream
Modified: branches/v0_99_maint/doc/_templates/indexsidebar.html
===================================================================
--- branches/v0_99_maint/doc/_templates/indexsidebar.html 2009-08-28
12:20:11 UTC (rev 7581)
+++ branches/v0_99_maint/doc/_templates/indexsidebar.html 2009-08-29
16:35:35 UTC (rev 7582)
@@ -52,7 +52,7 @@
but it is a good idea to ping us on the mailing list too.</p>
<p>For details on what's new, see the detailed <a href="{{
-pathto('_static/CHANGELOG', 1) }}">changelog</a>. Anything that could
+pathto('_static/CHANGELOG', 1) }}">changelog</a> or browse the <a
href="http://matplotlib.svn.sourceforge.net/viewvc/matplotlib/trunk/matplotlib/";>source
code</a>. Anything that could
require changes to your existing codes is logged in the <a href="{{
pathto('api/api_changes.html', 1) }}">api changes</a> file.</p>
Modified: branches/v0_99_maint/doc/_templates/layout.html
===================================================================
--- branches/v0_99_maint/doc/_templates/layout.html 2009-08-28 12:20:11 UTC
(rev 7581)
+++ branches/v0_99_maint/doc/_templates/layout.html 2009-08-29 16:35:35 UTC
(rev 7582)
@@ -4,7 +4,7 @@
{% block rootrellink %}
<li><a href="{{ pathto('index') }}">home</a>| </li>
<li><a href="{{ pathto('search') }}">search</a>| </li>
- <li><a href="examples/index.html">examples</a>| </li>
+ <li><a
href="http://matplotlib.sf.net/examples/index.html";>examples</a>| </li>
<li><a href="{{ pathto('gallery') }}">gallery</a>| </li>
<li><a href="{{ pathto('contents') }}">docs</a> »</li>
{% endblock %}
Modified: branches/v0_99_maint/doc/devel/coding_guide.rst
===================================================================
--- branches/v0_99_maint/doc/devel/coding_guide.rst 2009-08-28 12:20:11 UTC
(rev 7581)
+++ branches/v0_99_maint/doc/devel/coding_guide.rst 2009-08-29 16:35:35 UTC
(rev 7582)
@@ -1,4 +1,4 @@
-M.. _coding-guide:
+.. _coding-guide:
************
Coding guide
Added: branches/v0_99_maint/doc/users/image_tutorial.rst
===================================================================
--- branches/v0_99_maint/doc/users/image_tutorial.rst
(rev 0)
+++ branches/v0_99_maint/doc/users/image_tutorial.rst 2009-08-29 16:35:35 UTC
(rev 7582)
@@ -0,0 +1,324 @@
+.. _image_tutorial:
+
+
+**************
+Image tutorial
+**************
+
+.. _imaging_startup:
+
+Startup commands
+===================
+
+At the very least, you'll need to have access to the
:func:`~matplotlib.pyplot.imshow` function. There are a couple of ways to do
it. The easy way for an interactive environment::
+
+ $ipython -pylab -wthread
+
+The imshow function is now directly accessible (it's in your
+`namespace <http://bytebaker.com/2008/07/30/python-namespaces/>`_).
+See also :ref:`pyplot-tutorial`.
+
+The more expressive, easier to understand later method (use this in your
scripts to make it easier for others (including your future self) to read)::
+
+ $ipython -wthread
+
+.. sourcecode:: ipython
+
+ In [1]: import matplotlib.pyplot as plt
+ In [2]: import matplotlib.image as mpimg
+ In [3]: import numpy as np
+
+Examples below will use the latter method, for clarity. In these examples, if
you use the -pylab method, you can skip the "mpimg." and "plt." prefixes.
+
+.. _importing_data:
+
+Importing image data into Numpy arrays
+===============================================
+
+Plotting image data is supported by the Python Image Library (`PIL
<http://www.pythonware.com/products/pil/>`_), . Natively, matplotlib only
supports PNG images. The commands shown below fall back on PIL if the native
read fails.
+
+The image used in this example is a PNG file, but keep that PIL requirement in
mind for your own data.
+
+Here's the image we're going to play with:
+
+.. image:: ../_static/stinkbug.png
+
+It's a 24-bit RGB PNG image (8 bits for each of R, G, B). Depending
+on where you get your data, the other kinds of image that you'll most
+likely encounter are RGBA images, which allow for transparency, or
+single-channel grayscale (luminosity) images. You can right click on
+it and choose "Save image as" to download it to your computer for the
+rest of this tutorial.
+
+And here we go...
+
+.. sourcecode:: ipython
+
+ In [4]: img=mpimg.imread('stinkbug.png')
+ Out[4]:
+ array([[[ 0.40784314, 0.40784314, 0.40784314],
+ [ 0.40784314, 0.40784314, 0.40784314],
+ [ 0.40784314, 0.40784314, 0.40784314],
+ ...,
+ [ 0.42745098, 0.42745098, 0.42745098],
+ [ 0.42745098, 0.42745098, 0.42745098],
+ [ 0.42745098, 0.42745098, 0.42745098]],
+
+ [[ 0.41176471, 0.41176471, 0.41176471],
+ [ 0.41176471, 0.41176471, 0.41176471],
+ [ 0.41176471, 0.41176471, 0.41176471],
+ ...,
+ [ 0.42745098, 0.42745098, 0.42745098],
+ [ 0.42745098, 0.42745098, 0.42745098],
+ [ 0.42745098, 0.42745098, 0.42745098]],
+
+ [[ 0.41960785, 0.41960785, 0.41960785],
+ [ 0.41568628, 0.41568628, 0.41568628],
+ [ 0.41568628, 0.41568628, 0.41568628],
+ ...,
+ [ 0.43137255, 0.43137255, 0.43137255],
+ [ 0.43137255, 0.43137255, 0.43137255],
+ [ 0.43137255, 0.43137255, 0.43137255]],
+
+ ...,
+ [[ 0.43921569, 0.43921569, 0.43921569],
+ [ 0.43529412, 0.43529412, 0.43529412],
+ [ 0.43137255, 0.43137255, 0.43137255],
+ ...,
+ [ 0.45490196, 0.45490196, 0.45490196],
+ [ 0.4509804 , 0.4509804 , 0.4509804 ],
+ [ 0.4509804 , 0.4509804 , 0.4509804 ]],
+
+ [[ 0.44313726, 0.44313726, 0.44313726],
+ [ 0.44313726, 0.44313726, 0.44313726],
+ [ 0.43921569, 0.43921569, 0.43921569],
+ ...,
+ [ 0.4509804 , 0.4509804 , 0.4509804 ],
+ [ 0.44705883, 0.44705883, 0.44705883],
+ [ 0.44705883, 0.44705883, 0.44705883]],
+
+ [[ 0.44313726, 0.44313726, 0.44313726],
+ [ 0.4509804 , 0.4509804 , 0.4509804 ],
+ [ 0.4509804 , 0.4509804 , 0.4509804 ],
+ ...,
+ [ 0.44705883, 0.44705883, 0.44705883],
+ [ 0.44705883, 0.44705883, 0.44705883],
+ [ 0.44313726, 0.44313726, 0.44313726]]], dtype=float32)
+
+Note the dtype there - float32. Matplotlib has rescaled the 8 bit data from
each channel to floating point data between 0.0 and 1.0. As a side note, the
only datatype that PIL can work with is uint8. Matplotlib plotting can handle
float32 and uint8, but image reading/writing for any format other than PNG is
limited to uint8 data. Why 8 bits? Most displays can only render 8 bits per
channel worth of color gradation. Why can they only render 8 bits/channel?
Because that's about all the human eye can see. More here (from a photography
standpoint): `Luminous Landscape bit depth tutorial
<http://www.luminous-landscape.com/tutorials/bit-depth.shtml>`_
+
+Each inner list represents a pixel. Here, with an RGB image, there are 3
values. Since it's a black and white image, R, G, and B are all similar. An
RGBA (where A is alpha, or transparency), has 4 values per inner list, and a
simple luminance image just has one value (and is thus only a 2-D array, not a
3-D array). For RGB and RGBA images, matplotlib supports float32 and uint8
data types. For grayscale, matplotlib supports only float32. If your array
data does not meet one of these descriptions, you need to rescale it.
+
+.. _plotting_data:
+
+Plotting numpy arrays as images
+===================================
+
+So, you have your data in a numpy array (either by importing it, or by
generating it). Let's render it. In Matplotlib, this is performed using the
:func:`~matplotlib.pyplot.imshow` function. Here we'll grab the plot object.
This object gives you an easy way to manipulate the plot from the prompt.
+
+.. sourcecode:: ipython
+
+ In [5]: imgplot = plt.imshow(img)
+
+.. plot::
+
+ import matplotlib.pyplot as plt
+ import matplotlib.image as mpimg
+ import numpy as np
+ img = mpimg.imread('_static/stinkbug.png')
+ imgplot = plt.imshow(img)
+
+You can also plot any numpy array - just remember that the datatype must be
float32 (and range from 0.0 to 1.0) or uint8.
+
+.. _Pseudocolor:
+
+Applying pseudocolor schemes to image plots
+-------------------------------------------------
+
+Pseudocolor can be a useful tool for enhancing contrast and visualizing your
data more easily. This is especially useful when making presentations of your
data using projectors - their contrast is typically quite poor.
+
+Pseudocolor is only relevant to single-channel, grayscale, luminosity images.
We currently have an RGB image. Since R, G, and B are all similar (see for
yourself above or in your data), we can just pick on channel of our data:
+
+.. sourcecode:: ipython
+
+ In [6]: lum_img = img[:,:,0]
+
+This is array slicing. You can read more `here
<http://www.scipy.org/Tentative_NumPy_Tutorial>`_
+
+.. sourcecode:: ipython
+
+ In [7]: imgplot = mpimg.imshow(lum_img)
+
+.. plot::
+
+ import matplotlib.pyplot as plt
+ import matplotlib.image as mpimg
+ import numpy as np
+ img = mpimg.imread('_static/stinkbug.png')
+ lum_img = img[:,:,0]
+ plt.imshow(lum_img)
+
+Now, with a luminosity image, the default colormap (aka lookup table, LUT), is
applied. The default is called jet. There are plenty of others to choose
from. Let's set some others using the :meth:`~matplotlib.image.Image.set_cmap`
method on our image plot object:
+
+.. sourcecode:: ipython
+
+ In [8]: imgplot.set_cmap('hot')
+
+.. plot::
+
+ import matplotlib.pyplot as plt
+ import matplotlib.image as mpimg
+ import numpy as np
+ img = mpimg.imread('_static/stinkbug.png')
+ lum_img = img[:,:,0]
+ imgplot = plt.imshow(lum_img)
+ imgplot.set_cmap('hot')
+
+.. sourcecode:: ipython
+
+ In [9]: imgplot.set_cmap('spectral')
+
+.. plot::
+
+ import matplotlib.pyplot as plt
+ import matplotlib.image as mpimg
+ import numpy as np
+ img = mpimg.imread('_static/stinkbug.png')
+ lum_img = img[:,:,0]
+ imgplot = plt.imshow(lum_img)
+ imgplot.set_cmap('spectral')
+
+There are many other colormap schemes available. See a list and images of the
colormaps `here
<http://matplotlib.sourceforge.net/examples/pylab_examples/show_colormaps.html>`_
+
+.. _Color Bars
+
+Color scale reference
+------------------------
+
+It's helpful to have an idea of what value a color represents. We can do that
by adding color bars. It's as easy as one line:
+
+.. sourcecode:: ipython
+ In [10]: plt.colorbar()
+
+.. plot::
+
+ import matplotlib.pyplot as plt
+ import matplotlib.image as mpimg
+ import numpy as np
+ img = mpimg.imread('_static/stinkbug.png')
+ lum_img = img[:,:,0]
+ imgplot = plt.imshow(lum_img)
+ imgplot.set_cmap('spectral')
+ plt.colorbar()
+
+This adds a colorbar to your existing figure. This won't automatically change
if you change you switch to a different colormap - you have to re-create your
plot, and add in the colorbar again.
+
+.. _Data ranges
+
+Examining a specific data range
+---------------------------------
+
+Sometimes you want to enhance the contrast in your image, or expand the
contrast in a particular region while sacrificing the detail in colors that
don't vary much, or don't matter. A good tool to find interesting regions is
the histogram. To create a histogram of our image data, we use the
:func:`~matplotlib.pyplot.hist` function.
+
+.. sourcecode:: ipython
+
+ In[10]: plt.hist(lum_img)
+
+.. plot::
+
+ import matplotlib.pyplot as plt
+ import matplotlib.image as mpimg
+ import numpy as np
+ img = mpimg.imread('_static/stinkbug.png')
+ lum_img = img[:,:,0]
+ plt.hist(lum_img, range=(0.0,1.0))
+
+Most often, the "interesting" part of the image is around the peak, and you
can get extra contrast by clipping the regions above and/or below the peak. In
our histogram, it looks like there's not much useful information in the high
end (not many white things in the image). Let's adjust the upper limit, so
that we effectively "zoom in on" part of the histogram. We do this by calling
the :meth:`~matplotlib.image.Image.set_clim` method of the image plot object.
+
+.. sourcecode:: ipython
+
+ In[11]: imgplot.set_clim=(0.0,0.7)
+
+.. plot::
+
+ import matplotlib.pyplot as plt
+ import matplotlib.image as mpimg
+ import numpy as np
+ fig = plt.figure()
+ a=fig.add_subplot(1,2,1)
+ img = mpimg.imread('_static/stinkbug.png')
+ lum_img = img[:,:,0]
+ imgplot = plt.imshow(lum_img)
+ a.set_title('Before')
+ plt.colorbar(ticks=[0.1,0.3,0.5,0.7], orientation ='horizontal')
+ a=fig.add_subplot(1,2,2)
+ imgplot = plt.imshow(lum_img)
+ imgplot.set_clim(0.0,0.7)
+ a.set_title('After')
+ plt.colorbar(ticks=[0.1,0.3,0.5,0.7], orientation='horizontal')
+
+.. _Interpolation:
+
+Array Interpolation schemes
+-----------------------------------
+Interpolation calculates what the color or value of a pixel "should" be,
according to different mathematical schemes. One common place that this
happens is when you resize an image. The number of pixels change, but you want
the same information. Since pixels are discrete, there's missing space.
Interpolation is how you fill that space. This is why your images sometimes
come out looking pixelated when you blow them up. The effect is more
pronounced when the difference between the original image and the expanded
image is greater. Let's take our image and shrink it. We're effectively
discarding pixels, only keeping a select few. Now when we plot it, that data
gets blown up to the size on your screen. The old pixels aren't there anymore,
and the computer has to draw in pixels to fill that space.
+
+.. sourcecode:: ipython
+
+ In [8]: import Image
+ In [9]: img = Image.open('stinkbug.png') # Open image as PIL image
object
+ In [10]: rsize = img.resize((img.size[0]/10,img.size[1]/10)) # Use PIL to
resize
+ In [11]: rsizeArr = np.asarray(rsize) # Get array back
+ In [12]: imgplot = mpimg.imshow(rsizeArr)
+
+.. plot::
+
+ import matplotlib.pyplot as plt
+ import matplotlib.image as mpimg
+ import numpy as np
+ import Image
+ img = Image.open('_static/stinkbug.png') # opens the file using PIL -
it's not an array yet
+ rsize = img.resize((img.size[0]/10,img.size[1]/10)) # resize the image
+ rsizeArr = np.asarray(rsize)
+ lum_img = rsizeArr[:,:,0]
+ imgplot = plt.imshow(rsizeArr)
+
+Here we have the default interpolation, bilinear, since we did not give
:func:`~matplotlib.pyplot.imshow` any interpolation argument.
+
+Let's try some others:
+
+.. sourcecode:: ipython
+
+ In [10]: imgplot.set_interpolation('nearest')
+
+.. plot::
+
+ import matplotlib.pyplot as plt
+ import matplotlib.image as mpimg
+ import numpy as np
+ import Image
+ img = Image.open('_static/stinkbug.png') # opens the file using PIL -
it's not an array yet
+ rsize = img.resize((img.size[0]/10,img.size[1]/10)) # resize the image
+ rsizeArr = np.asarray(rsize)
+ lum_img = rsizeArr[:,:,0]
+ imgplot = plt.imshow(rsizeArr)
+ imgplot.set_interpolation('nearest')
+
+.. sourcecode:: ipython
+
+ In [10]: imgplot.set_interpolation('bicubic')
+
+.. plot::
+
+ import matplotlib.pyplot as plt
+ import matplotlib.image as mpimg
+ import numpy as np
+ import Image
+ img = Image.open('_static/stinkbug.png') # opens the file using PIL -
it's not an array yet
+ rsize = img.resize((img.size[0]/10,img.size[1]/10)) # resize the image
+ rsizeArr = np.asarray(rsize)
+ lum_img = rsizeArr[:,:,0]
+ imgplot = plt.imshow(rsizeArr)
+ imgplot.set_interpolation('bicubic')
+
+Bicubic interpolation is often used when blowing up photos - people tend to
prefer blurry over pixelated.
\ No newline at end of file
Modified: branches/v0_99_maint/doc/users/index.rst
===================================================================
--- branches/v0_99_maint/doc/users/index.rst 2009-08-28 12:20:11 UTC (rev
7581)
+++ branches/v0_99_maint/doc/users/index.rst 2009-08-29 16:35:35 UTC (rev
7582)
@@ -19,6 +19,7 @@
customizing.rst
shell.rst
index_text.rst
+ image_tutorial.rst
artists.rst
legend_guide.rst
event_handling.rst
Modified: branches/v0_99_maint/doc/users/transforms_tutorial.rst
===================================================================
--- branches/v0_99_maint/doc/users/transforms_tutorial.rst 2009-08-28
12:20:11 UTC (rev 7581)
+++ branches/v0_99_maint/doc/users/transforms_tutorial.rst 2009-08-29
16:35:35 UTC (rev 7582)
@@ -1,4 +1,4 @@
-.. _transformstutorial:
+.. _transforms_tutorial:
**************************
Transformations Tutorial
Modified: branches/v0_99_maint/doc/users/whats_new.rst
===================================================================
--- branches/v0_99_maint/doc/users/whats_new.rst 2009-08-28 12:20:11 UTC
(rev 7581)
+++ branches/v0_99_maint/doc/users/whats_new.rst 2009-08-29 16:35:35 UTC
(rev 7582)
@@ -12,6 +12,16 @@
.. _whats-new-mplot3d:
+New documentation
+-----------------
+
+Jae-Joon Lee has written two new guides :ref:`plotting-guide-legend`
+and :ref:`plotting-guide-annotation`. Michael Sarahan has written
+:ref:`image_tutorial`. John Hunter has written two new tutorials on
+working with paths and transformations: :ref:`path_tutorial` and
+:ref:`transforms_tutorial`.
+
+
mplot3d
--------
@@ -53,12 +63,6 @@
.. plot:: pyplots/whats_new_99_spines.py
-New documentation
------------------
-
-jae-Joon Lee has written two new guides :ref:`plotting-guide-legend`
-and :ref:`plotting-guide-annotation`.
-
.. _whats-new-0-98-4:
new in 0.98.4
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