Thread: [matplotlib-devel] Pylab example (gradient_bar.py) only works for png

Hi

The gradient_bar example flips the bars using svg, pdf and eps backends.

Add
fig.savefig("gradient_bar.png")
fig.savefig("gradient_bar.pdf")
fig.savefig("gradient_bar.eps")
fig.savefig("gradient_bar.svg")

to gradient_bar.py to reproduce.

Tested with TkAgg backend (pylab: 1.3.0.dev5867 on python 2.5.2).

Arnar

There's a bug filed for this.  I've looked at it a few times, but I'm 
not sure how the image flipping parameters are "supposed" to work.  
Anyone else want to have a look at this?

https://sourceforge.net/tracker2/?func=detail&aid=2160909&group_id=80706&atid=560720

Mike

Arnar Flatberg wrote:
> Hi
>
> The gradient_bar example flips the bars using svg, pdf and eps backends.
>
> Add
> fig.savefig("gradient_bar.png")
> fig.savefig("gradient_bar.pdf")
> fig.savefig("gradient_bar.eps")
> fig.savefig("gradient_bar.svg")
>
> to gradient_bar.py to reproduce.
>
> Tested with TkAgg backend (pylab: 1.3.0.dev5867 on python 2.5.2).
>
> Arnar
>
>
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-- 
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

On Tue, Oct 28, 2008 at 4:20 PM, Michael Droettboom <md...@st...> wrote:

> There's a bug filed for this.  I've looked at it a few times, but I'm not
> sure how the image flipping parameters are "supposed" to work.  Anyone else
> want to have a look at this?
>
>
> https://sourceforge.net/tracker2/?func=detail&aid=2160909&group_id=80706&atid=560720
>

I was not aware of that, thanks Michael. Just to be clear, (in relation to
the filed ticket), the screen image is just fine for my part, its *only*
after saving in any vector graphic format I get a "flipped" image as a
result. In other words, I have an issue with savefig, while the ticket is
concerned with imshow. Perhaps they are obviously related ... then Im sorry
for the noise :-)

Thanks,

Arnar

No problem.  I didn't mean to imply that you should have known you bug 
was a duplicate.  I was mainly pointing it out for other developers to 
keep track of the issue, since I suspect your issue and the one in the 
bug are the same, but that's probably not obvious to most users.

I suspect the fix is as simple as twiddling a single line of code, it's 
just not obvious to me how the image flipping is supposed to work to 
have consistent behavior across backends -- and I hope another developer 
here has a clue...

Thanks for your report,
Mike

Arnar Flatberg wrote:
>
>
> On Tue, Oct 28, 2008 at 4:20 PM, Michael Droettboom <md...@st... 
> <mailto:md...@st...>> wrote:
>
>     There's a bug filed for this.  I've looked at it a few times, but
>     I'm not sure how the image flipping parameters are "supposed" to
>     work.  Anyone else want to have a look at this?
>
>     https://sourceforge.net/tracker2/?func=detail&aid=2160909&group_id=80706&atid=560720
>     <https://sourceforge.net/tracker2/?func=detail&aid=2160909&group_id=80706&atid=560720>
>
>
> I was not aware of that, thanks Michael. Just to be clear, (in 
> relation to the filed ticket), the screen image is just fine for my 
> part, its *only* after saving in any vector graphic format I get a 
> "flipped" image as a result. In other words, I have an issue with 
> savefig, while the ticket is concerned with imshow. Perhaps they are 
> obviously related ... then Im sorry for the noise :-)
>
> Thanks,
>
> Arnar
>

-- 
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

> I suspect the fix is as simple as twiddling a single line of code, it's 
> just not obvious to me how the image flipping is supposed to work to 
> have consistent behavior across backends -- and I hope another developer 
> here has a clue...

I suspect this is related to the problem described at

http://thread.gmane.org/gmane.comp.python.matplotlib.general/14420

The problem does not seem to be alignment but that the image is rendered
upside down. The PDF backend does

    img.flipud_out()
    # get rgba data of image and write it in the output file
    img.flipud_out()

and if I comment out the flipud_out calls, I get that particular case
right but then the image_origin example is wrong.

Revision 5618 added a flipud_out call to Axes.draw:

            if self.images[0].origin=='upper':
                im.flipud_out()

The log message is:

------------------------------------------------------------------------
r5618 | jdh2358 | 2008-06-20 20:09:12 +0300 (Pe, 20 Kes 2008) | 1 line
Changed paths:
   M /trunk/matplotlib/examples/api/mathtext_asarray.py
   M /trunk/matplotlib/examples/pylab_examples/figimage_demo.py
   M /trunk/matplotlib/lib/matplotlib/axes.py
   M /trunk/matplotlib/lib/matplotlib/backends/backend_gtkagg.py
   M /trunk/matplotlib/lib/matplotlib/figure.py
   M /trunk/matplotlib/src/_gtkagg.cpp
   M /trunk/matplotlib/src/_image.cpp

added origin support for composite images
------------------------------------------------------------------------

I think this was discussed further in some emails between me, Haibao
Tang, and John Hunter, but at least I have been too busy to spend much
time on matplotlib lately. I hope this helps somebody track the bug
down.

Jouni