John,
I made some more changes in quiver, and I think they will ensure that
dpi changes are handled correctly as far as arrows are concerned, both
in the plot and in the key.
There is still a problem with the key label, and it can be seen clearly
in the attached slight modification of quiver_demo.py. There are
actually two visible problems:
1) The hline generated by frac is too long with dpi=50.
2) The positioning and sizing of the key bbox are also dpi-dependent, as
I verified by using your bbox-display trick.
I went hunting through text.py, mathtext.py, backend_bases, and
backend_agg without figuring out where the problem is. The right dpi
seems to be getting used at mathtext parsing time. Maybe it is not
actually getting propagated all the way into the code that gets the font
metrics. I did not try to trace it that far.
Along the way, I found that in backend_bases, print_figure was doing
what appears to be a completely unnecessary draw operation after
restoring the original dpi, so I commented that out. This speeds up
backend_driver.py agg by a few percent.
Eric
John Hunter wrote:
On Sat, Apr 26, 2008 at 2:04 PM, Eric Firing <[EMAIL PROTECTED]> wrote:
The attached script, run on svn mpl, illustrates a positioning problem: note
that the subplot titles are badly positioned in the 50 dpi version. I
believe that changing from 150 to 50 dpi should yield a perfect scaling of
everything in the plot, but it doesn't. There is a similar problem with a
quiver key positioned outside the axes frame, but I don't have a trivial
example yet; I am hoping that whatever solves the title positioning problem
will take care of that also. If not, I will make a simple example and we
can attack it separately.
There were two problems with title positioning. The first was that
the title offset transformation was hardcoded in pixels and not dpi,
and the second was that is was not getting notifed when the figure dpi
was changed. I changed the offset to read:
self.titleOffsetTrans = mtransforms.Affine2D().translate(
0.0, 5.0*self.figure.dpi/72.)
and added a callbacks registry to the figure instance so that
observers could be notified when dpi was changed (dpi used to be a
lazy value on the maintenance branch but is a plain-ol-value on the
trunk).
def on_dpi_change(fig):
self.titleOffsetTrans.clear().translate(
0.0, 5.0*fig.dpi/72.)
self.figure.callbacks.connect('dpi_changed', on_dpi_change)
It looks like the problem in the quiver code is that the "labelsep"
property reads the dpi when the QuiverKey is intiitalized but does not
get notified on dpi change. I added a callback there too so you
should test to see if this helps. The dpi setting is also referenced
in the _set_transform method. Since you are more familiar with the
quiver code that I am, and this hint may point you in the right
direction, I'll let you take a look at that and see if a callback is
needed.
On a related note, one trick I use when debugging text layout problems
is to turn on the "bbox". If the bbox is right but the text is in the
wrong place, you know it is in the layout. If the bbox is in the
wrong place, you know the problem is in the font metrics:
boxprops = dict(facecolor='red')
ax1.set_title('Top Plot', bbox=boxprops)
JDH
'''
Demonstration of quiver and quiverkey functions. This is using the
new version coming from the code in quiver.py.
Known problem: the plot autoscaling does not take into account
the arrows, so those on the boundaries are often out of the picture.
This is *not* an easy problem to solve in a perfectly general way.
The workaround is to manually expand the axes.
'''
import sys
import matplotlib
matplotlib.use('agg')
from pylab import *
X,Y = meshgrid( arange(0,2*pi,.2),arange(0,2*pi,.2) )
U = cos(X)
V = sin(Y)
#1
figure()
Q = quiver( U, V)
qk = quiverkey(Q, 0.5, 0.92, 2, r'$2 \frac{m}{s}$', labelpos='W',
fontproperties={'weight': 'bold'})
l,r,b,t = axis()
dx, dy = r-l, t-b
axis([l-0.05*dx, r+0.05*dx, b-0.05*dy, t+0.05*dy])
title('Minimal arguments, no kwargs')
savefig('q1_050.png', dpi=50)
savefig('q1_150.png', dpi=150)
#2
figure()
Q = quiver( X, Y, U, V, units='width')
qk = quiverkey(Q, 0.9, 0.95, 2, r'$2 \frac{m}{s}$',
labelpos='E',
coordinates='figure',
fontproperties={'weight': 'bold'})
axis([-1, 7, -1, 7])
title('scales with plot width, not view')
savefig('q2_050.png', dpi=50)
savefig('q2_150.png', dpi=150)
#3
figure()
Q = quiver( X[::3, ::3], Y[::3, ::3], U[::3, ::3], V[::3, ::3],
pivot='mid', color='r', units='inches' )
qk = quiverkey(Q, 0.5, 0.03, 1, r'$1 \frac{m}{s}$', fontproperties={'weight': 'bold'})
plot( X[::3, ::3], Y[::3, ::3], 'k.')
axis([-1, 7, -1, 7])
title("pivot='mid'; every third arrow; units='inches'")
savefig('q3_050.png', dpi=50)
savefig('q3_150.png', dpi=150)
#4
figure()
M = sqrt(pow(U, 2) + pow(V, 2))
Q = quiver( X, Y, U, V, M, units='x', pivot='tip', width=0.022, scale=1/0.15)
qk = quiverkey(Q, 0.9, 1.05, 1, r'$1 \frac{m}{s}$',
labelpos='E',
fontproperties={'weight': 'bold'})
plot(X, Y, 'k.')
axis([-1, 7, -1, 7])
title("scales with x view; pivot='tip'")
savefig('q4_050.png', dpi=50)
savefig('q4_150.png', dpi=150)
#5
figure(dpi=50)
Q = quiver( X[::3, ::3], Y[::3, ::3], U[::3, ::3], V[::3, ::3],
color='r', units='x',
linewidths=(2,), edgecolors=('k'), headaxislength=5 )
qk = quiverkey(Q, 0.5, 0.03, 1, r'$1 \frac{m}{s}$', fontproperties={'weight': 'bold'})
axis([-1, 7, -1, 7])
title("triangular head; scale with x view; black edges")
savefig('q5_050.png', dpi=50)
savefig('q5_150.png', dpi=150)
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