Drawing polygons on separate layers

[domagojhack]

I am building an app that uses user input to draw polygons on EOmaps using a custom click callback.

Currently, I can achieve this with:

import geopandas as gpd
from eomaps import Maps
import matplotlib
from matplotlib import collections
import matplotlib.pyplot as plt

from shapely.geometry import Polygon
import geopandas as gpd


poly = []

m = Maps(layer="DEM")

data = m.read_file.GeoTIFF(
    "base_layers/dem/halasevo.tif")

m.set_shape.shade_raster()
m.set_data(**data)
m.plot_map(cmap="gist_earth")

a = [[]]


def map_click_callback(**kwargs):
    pos = kwargs["pos"]
    global m
    global poly
    global a

    poly.append(pos)

    m.set_shape.shade_raster()
    m.set_data(**data)
    m.plot_map(cmap="gist_earth")

    m.add_marker(
        xy=pos, radius=20, shape="ellipses",
        fc="none", ec="r", hatch="///", lw=2, n=100)

    print("col")
    for idx, i in enumerate(m.ax.collections[:]):
        print(idx, i)
        if type(i) == matplotlib.collections.PatchCollection:
            m.ax.collections.pop(idx)
            print("removed", idx)

    if len(poly) >= 3:
        shape = Polygon(poly)
        gdf = gpd.GeoDataFrame({"name": poly, "geometry": shape}, crs="4326")
        m.add_gdf(gdf, hatch="///", ec="b", alpha=.3)

    m.redraw()

m.cb.click.attach(map_click_callback)

m.show()

Currently, I am drawing my polygons on the same layer by redrawing my layer with every click.
Ideally, I would like to have a separate layer for my polygon that is simultaneously visible with my base layer. I cannot wrap my head around the best solution for it. For now, my idea is to create a separate layer that contains the base map and my polygon.

Is there a right way to do this?

[raphaelquast]

Hey, yep that idea crossed my mind as well😄
Yes there is in fact a better way to do this!
It's a bit more complicated to implement, but the good news is I actually have a working example on this (it's been on my list of to-do's for a while but it has never been finished so far...)

Unfortunately I'm currently a bit short on time, but I'll try to upload the relevant pieces to a branch soon... would you be willing to finalize it together so that it can be added in an upcoming EOmaps release?
(the code I have also supports exporting the polygons to shapefiles once they are drawn but the api is not very mature yet)

[raphaelquast]

@domagojhack OK, I've uploaded my prove-of-concept for a proper EOmaps-drawer to the "draw" branch and opened a "work-in-progress" pull-request #90 . I've also added some basic comments on how to use the feature at the moment in #90 .
In case you manage to build upon the work I did there so far I'd be grateful if you could add any improvements (e.g. as pull-requests to this branch) and I'll of course contribute and provide assistance along the way to make this feature a reality sometime in the future.

At the moment really nothing of this should be seen as "fixed"... rather as a first try to see how well this could work (and I think it shows that it has the potential to be awesome 😄)
I'm open to discuss/change how the current interface is set-up and I'm happy on any constructive feedback you can provide!

[domagojhack]

I pulled the branch. Gonna start to experiment with drawer and keep you posted.

[raphaelquast]

Awesome! I just realized that your initial question was actually about how to put the polygons on separate layers... I've added a quick commit to implement that just now!

Here's how it works at the moment:

m = Maps(layer="base")
m.add_feature.preset.coastline()
m2 = m.new_layer(layer="second layer")
m2.add_feature.preset.ocean()

m.util.layer_selector()

# these draws will go onto the currently active layer
# (e.g. use the layer-selector widget to select the layer you want to draw on)
m.util.draw.circle()
m.util.draw.rectangle()

# this one will always end up on the "second layer"
# (you can draw on any layer but once you are finished it will be put on "second layer")
d1 = m.util.draw.new_poly(layer="second layer")
d1.polygon()

[domagojhack]

I just got back from fieldwork and continue doing my project that uses EOmaps.

[raphaelquast]

nice 🙂 I've merged all recent changes (e.g. v4.3) into the draw branch to keep it up to date
(there were no conflicting changes)