Interesting!

So, my approach in this case would be:

1. Write a block that takes the data from your flow graph, and converts
it to a format (e.g. JSON, KML, GPX,…) that makes sense for the
receiving end. This data should be emitted as messages (not python
variables).
2. use a UDP or ZeroMQ (I recommend the latter) to send these messages out
3. Write a really minimal web application that receives the things from
2. and updates a browser visualization. Use your own images or simply
OpenStreetMap as base layer.

You can of course also write your own visualization block. That's
absolutely feasible; it's just that matplotlib is really not the tool of
choice for that here. But it's definitely not the software you need,
either, to draw points on an image. There's literally dozens of python
toolkits that can display images and modify them.

Writing visualization blocks will require you to think about how to
thread them. And since it'll be hard for the block to interact with the
main thread, but that would be necessary for GUI blocks to work, I don't
know whether that is an entry level project. Anyway, do have a look at
Tim O'Shea gr-pyqt ; it contains python visualization blocks, and I
don't think it'll be hard to understand and modify them. Look at the
raster_plot.py for example.

Best regards,

Marcus

On 09/20/2017 10:21 PM, Ali wrote:
> Hi,
>
> Actually I want to draw coordinates on a map. So I want to upload a
> map(a png file, like using imshow function in MATLAB, matplotlib) and
> then draw points on this map. I think it is not possible by just using
> QT instruments. 
>
> Regards,
> Ali
>
> 2017-09-20 21:14 GMT+03:00 Marcus Müller <marcus.muel...@ettus.com
> <mailto:marcus.muel...@ettus.com>>:
>
>     Dear Ali,
>
>     don't convert data streams to Python variables. Just use the Qt
>     instrumentation plots that directly come with GNU Radio, they are
>     actually meant for this.
>
>     Matplotlib is *definitely* not what you want to use for live
>     plots. Far too slow.
>
>     Best regards,
>
>     Marcus
>
>
>     On 09/20/2017 01:29 AM, Ali wrote:
>>     Hi everyone,
>>
>>     I have a flowchart in which USRP's are running and after some
>>     blocks 2 variables are produced at the output.
>>
>>     As the inputs change, outputs change. I want to _dynamically_
>>     plot these two variables on x and y axis. I am willing to use
>>     matplotlib.
>>
>>     What do you suggest to plot these variables?
>>
>>     1- Write them to a .txt file and read by matplotlib at the same time,
>>     2- Without writing the variable anywhere, directly use in
>>     matplotlib(somehow)
>>     3- Write a python block and use in GRC directly
>>
>>     I don't know whether these can be applied or not. I am open to
>>     any ideas.
>>
>>     Regards,
>>     Ali
>>
>>
>>
>>
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