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. I have made a first attempt to figure out the cause of the positioning problem, and I have failed; I hope someone else will find it easier to track down. I also find that following the chain of events involved in savefig, and following the dpi setting, is rather difficult, and I wonder whether it might be possible to clarify and simplify anything. In any case, the dpi-related positioning bug (or bugs) is a significant problem for me now. Eric
On Sat, Apr 26, 2008 at 2:04 PM, Eric Firing <ef...@ha...> 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
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 <ef...@ha...> 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
On Sun, Apr 27, 2008 at 3:14 AM, Eric Firing <ef...@ha...> wrote: > 1) The hline generated by frac is too long with dpi=50. The problem with the hline appears to be that the width of the line in the frac has a component that depends on the thickness thickness = state.font_output.get_underline_thickness( state.font, state.fontsize, state.dpi) width = max(num.width, den.width) + thickness * 10. and get_underline_thickness here is defaulting to 1.0 because of this max call in get_underline_thickness return max(1.0, cached_font.font.underline_thickness / 64.0 / fontsize * 10.0) Michael -- what is the role of these 10.0 scale factors, which is showing up in both the frac call and the get_underline_thickness? Is this something from Knuth, or is it a fudge factor that gets it mostly right? I suspect we will need something like width = max(num.width, den.width) + thickness * 10. * state.dpi/72. but with this change the frac bar looks a little too wide -- which is why I'm wondering if there is something magic about 10. or if another number might serve better. > 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. I think you are right here -- because we are creating a new FigureCanvas and hence a new renderer in the switch_backend call we do not need to redraw the original figure with the original facecolor, edgecolor and dpi params. In older versions of mpl, if memory serves correctly, calling savefig would reuse the same renderer so after the print to hardcopy we would redraw so the figure in the GUI window would look right. But I agree this looks superfluous in light of the current code which is creating a new canvas with each savefig. JDH
John Hunter wrote: > On Sun, Apr 27, 2008 at 3:14 AM, Eric Firing <ef...@ha...> wrote: > > >> 1) The hline generated by frac is too long with dpi=50. >> > > The problem with the hline appears to be that the width of the line in > the frac has a component that depends on the thickness > > thickness = state.font_output.get_underline_thickness( > state.font, state.fontsize, state.dpi) > width = max(num.width, den.width) + thickness * 10. > > and get_underline_thickness here is defaulting to 1.0 because of this > max call in get_underline_thickness > > return max(1.0, cached_font.font.underline_thickness / 64.0 / > fontsize * 10.0) > I believe that this is where the dpi needs to be factored in. Ft2font (well, freetype, really) seems to scale metrics for individual glyphs by dpi, but not the font-global metrics. I had wrongly assumed they were all scaled by dpi. So this is a subtler instance of the recent x-height bug that caused sub/superscripts to be incorrect at different dpi's. > Michael -- what is the role of these 10.0 scale factors, which is > showing up in both the frac call and the get_underline_thickness? Is > this something from Knuth, or is it a fudge factor that gets it mostly > right? I suspect we will need something like > > width = max(num.width, den.width) + thickness * 10. * state.dpi/72. > This 10.0 is from Knuth. It is the amount of overhang of the fraction beam, and is meant to be relative to the thickness of the beam itself. The other 10.0 (in get_underline_thickness) is my own experimental fudge to deal with the peculiarities of how underline thickness is stored in Truetype fonts. (Remember "pure" TeX uses a completely different font metric standard, so some mapping from TrueType/freetype etc. had to be fudged on.) What's causing the fraction bar to be too wide at lower dpi is the minimum underline thickness of 1.0 enforced in get_underline_thickness. I think that was a mistake -- enforcing 1.0 pixel lines should happen closer to the backend level -- so I've removed the max(1.0, ...) there. > but with this change the frac bar looks a little too wide -- which is > why I'm wondering if there is something magic about 10. or if another > number might serve better. > -- Michael Droettboom Science Software Branch Operations and Engineering Division Space Telescope Science Institute Operated by AURA for NASA
John,
Thank you very much--that's a big help. Some time today or tomorrow I
will try to track down any remaining quiver problems. I suspect similar
dpi-related problems may lurk elsewhere as well.
Those lazy values worked pretty well!
One of the things that puzzles me is the following method of
FigureCanvasAgg in backend_agg:
def print_png(self, filename_or_obj, *args, **kwargs):
FigureCanvasAgg.draw(self)
renderer = self.get_renderer()
original_dpi = renderer.dpi
renderer.dpi = self.figure.dpi
if type(filename_or_obj) in (str, unicode):
filename_or_obj = open(filename_or_obj, 'w')
self.get_renderer()._renderer.write_png(filename_or_obj,
self.figure.dpi)
renderer.dpi = original_dpi
The FigureCanvasAgg.draw(self) command gets turned into
self.figure.draw(self.renderer), which is executed *before* the
renderer.dpi gets set to self.figure.dpi, so it seems like there is the
possibility of an inconsistency. I suspect there is no problem in
practice, but it is confusing.
Now that I look again, it looks like what is happening is that the
get_renderer call in FigureCanvasAgg.draw is setting the renderer dpi to
the figure dpi, as well as setting self.renderer, in which case most of
the code in print_png seems to be superfluous.
Mostly unrelated question: is there any point in keeping
backend_agg2.py, or at least keeping it in the backends directory?
Maybe it is time to move that and backend_emf.py (and maybe others) to
some sort of cold storage, in case someone is inspired later to
resurrect them.
Eric
John Hunter wrote:
> On Sat, Apr 26, 2008 at 2:04 PM, Eric Firing <ef...@ha...> 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
Eric Firing wrote: > 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. The plot thickens. The postscript backend is completely confused by the quiver plot. Try the attached example. pdf seems OK. Eric
On Sun, Apr 27, 2008 at 12:56 PM, Eric Firing <ef...@ha...> wrote:
> The plot thickens. The postscript backend is completely confused by the
> quiver plot. Try the attached example.
Argg, that was a subtle one -- there was a bug in backend ps which was
exposed only if you are using a path collection with offsets,
transoffset and clippath and cliprect both None. In that scenario,
the translate in the bind def function was not getting wrapped in a
gsave/grestore pair, which was causing the axes to be drawn in the
wrong place because the translate from the offset remained in effect.
I tried following the draw_markers logic and putting the
gsave/grestore in the ps_cmd, eg in draw_markers Michael writes ijn a
comment:
ps_cmd = ['/o {', 'gsave', 'newpath', 'translate'] # dont want
the translate to be global
so clearly he was bumping up against the same problem with markers.
For some reason, trying the same thing in the path_collection was not
working for me, so I resorted to the somewhat hackish approach of
forcing _draw_ps to wrap a gsave/grestore if it wasn't getting one
from the cliprect or clippath:
needwrap = not (clippath or cliprect)
if needwrap:
# we need to make sure that there is at least 1
# save/grestore around each ps write so we'll force it if
# we're not getting one from the cliprecot or clippath.
# hackish, yes
write('gsave\n')
and then
if needwrap:
write('grestore\n')
I think there will be cleaner way, but it will need some fresh
eyeballs tomorrow and this will provide a temporary fix.
JDH
On Sun, Apr 27, 2008 at 8:28 PM, John Hunter <jd...@gm...> wrote: > Argg, that was a subtle one -- there was a bug in backend ps which was > exposed only if you are using a path collection with offsets, > transoffset and clippath and cliprect both None. In that scenario, > the translate in the bind def function was not getting wrapped in a One thing I failed to make clear: the artist with said properties is quiver.QuiverKey.vector JDH
John Hunter wrote:
> On Sun, Apr 27, 2008 at 12:56 PM, Eric Firing <ef...@ha...> wrote:
>
>> The plot thickens. The postscript backend is completely confused by the
>> quiver plot. Try the attached example.
>
>
> Argg, that was a subtle one -- there was a bug in backend ps which was
> exposed only if you are using a path collection with offsets,
> transoffset and clippath and cliprect both None. In that scenario,
> the translate in the bind def function was not getting wrapped in a
> gsave/grestore pair, which was causing the axes to be drawn in the
> wrong place because the translate from the offset remained in effect.
> I tried following the draw_markers logic and putting the
> gsave/grestore in the ps_cmd, eg in draw_markers Michael writes ijn a
> comment:
>
> ps_cmd = ['/o {', 'gsave', 'newpath', 'translate'] # dont want
> the translate to be global
>
> so clearly he was bumping up against the same problem with markers.
> For some reason, trying the same thing in the path_collection was not
> working for me, so I resorted to the somewhat hackish approach of
> forcing _draw_ps to wrap a gsave/grestore if it wasn't getting one
> from the cliprect or clippath:
>
> needwrap = not (clippath or cliprect)
> if needwrap:
> # we need to make sure that there is at least 1
> # save/grestore around each ps write so we'll force it if
> # we're not getting one from the cliprecot or clippath.
> # hackish, yes
> write('gsave\n')
>
> and then
>
> if needwrap:
> write('grestore\n')
>
> I think there will be cleaner way, but it will need some fresh
> eyeballs tomorrow and this will provide a temporary fix.
I went ahead and committed an alternative fix that I think is cleaner,
and greatly reduces the number of needless gsave/grestore pairs. Your
version of the method is still there, with a mangled name, for easy
reference and testing until we are sure which way to go.
Sorry for whatever duplicated effort there has been. I did not intend
to spend a fair chunk of the day working on this, but I let myself get
sucked in. It was a challenge.
As mentioned in a message a few minutes ago that I don't think went to
the list, my gs interpreter is choking on the apostrophe (single quote)
character, as in title or label strings. I can't find any reason why
this should cause trouble--maybe it is a particular version or
configuration of gs.
Eric