matplotlib-devel Mailing List for matplotlib (Page 4)

Thank you,
 Seb

In some cases, there appears to be a bug in SVG image handling. For
example, the image in the colorbar is not properly sized
 import pylab as p
 p.imshow(p.rand(5,3))
 p.colorbar()
 p.savefig('test.svg')g
 p.show()
This problem appeared before and after Steve's application of
Norbert's PNG patch (thanks's Norbert!) so it looks like something
else is to blame. See also contourf_demo, in which SVG appears broken
in a perhaps unrelated way.
On the subject, Steve asked offlist whether Agg could write to a file
object rather than disc, which obviate the need to create a temporary
PNG which is subsequently embedded in the SVG file.
I tried this several months ago. The relevant code is src/_image.cpp
Image::write_png where we do
 std::string fileName = Py::String(args[0]);
 const char *file_name = fileName.c_str();
 FILE *fp;
 png_structp png_ptr;
 fp = fopen(file_name, "wb");
 ...snip...
 png_init_io(png_ptr, fp);
At one point I tried to figure out how to make this work with
StringIO, but was stumped because PNG appears to require a file
pointer and StringIO doesn't emulate this at extension code level, as
far as I can see. Anyone know otherwise? Maybe a question for
python-list....
JDH

>>>>> "sebastian" == sebastian rooks <seb...@fr...> writes:
 sebastian> Could it be changed such that figaspect takes a float
 sebastian> as its argument and the 2 lines to compute arr_ratio
 sebastian> are moved from figaspect to matshow before calling
 sebastian> figaspect ? (+ change the figaspect doc string) It will
 sebastian> make figaspect more general and allow us to create a
 sebastian> figure with a given aspect ratio without
 sebastian> copying/pasting of nearly all the figaspect machinery.
Good idea -- I overloaded figaspect to do both (it works with either
an array or a number argument). Code is below and in CVS
 Checking in lib/matplotlib/figure.py;
 /cvsroot/matplotlib/matplotlib/lib/matplotlib/figure.py,v <-- figure.py
 new revision: 1.34; previous revision: 1.33
 sebastian> 2/ Does anybody intend to add a Patch object to draw
 sebastian> polygons with holes (I do not know how to do it) ?
Not presently, but this would be nice.
JDH
def figaspect(arg):
 """
 Create a figure with specified aspect ratio. If arg is a number,
 use that aspect ratio. If arg is an array, figaspect will
 determine the width and height for a figure that would fit array
 preserving aspcect ratio. The figure width, height in inches are
 returned. Be sure to create an axes with equal with and height,
 eg
 Example usage:
 # make a figure twice as tall as it is wide
 w, h = figaspect(2.)
 fig = Figure(figsize=(w,h))
 ax = fig.add_axes([0.1, 0.1, 0.8, 0.8])
 ax.imshow(A, **kwargs)
 # make a figure with the proper aspect for an array
 A = rand(5,3)
 w, h = figaspect(A)
 fig = Figure(figsize=(w,h))
 ax = fig.add_axes([0.1, 0.1, 0.8, 0.8])
 ax.imshow(A, **kwargs)
 Thanks to Fernando Perez for this function
 """
 isarray = hasattr(arg, 'shape')
 
 # min/max sizes to respect when autoscaling. If John likes the idea, they
 # could become rc parameters, for now they're hardwired.
 figsize_min = array((4.0,2.0)) # min length for width/height
 figsize_max = array((16.0,16.0)) # max length for width/height
 #figsize_min = rcParams['figure.figsize_min']
 #figsize_max = rcParams['figure.figsize_max']
 # Extract the aspect ratio of the array
 if isarray:
 nr,nc = arg.shape[:2]
 arr_ratio = float(nr)/nc
 else:
 arr_ratio = float(arg)
 # Height of user figure defaults
 fig_height = rcParams['figure.figsize'][1]
 # New size for the figure, keeping the aspect ratio of the caller
 newsize = array((fig_height/arr_ratio,fig_height))
 # Sanity checks, don't drop either dimension below figsize_min
 newsize /= min(1.0,*(newsize/figsize_min))
 # Avoid humongous windows as well
 newsize /= max(1.0,*(newsize/figsize_max))
 # Finally, if we have a really funky aspect ratio, break it but respect
 # the min/max dimensions (we don't want figures 10 feet tall!)
 newsize = clip(newsize,figsize_min,figsize_max)
 return newsize