Overlay/Fill country boundaries with image in

Question

Is there a way to fill a country with an image similar to R solution using custom library here:

I have a solution where the face colour is filled for instance the below where Italy is blue. However, I would like to add the Italian flag. Is there a way in Python (I have not found much after searching) or is something like QGIS needed:

#create a map where I can load images in to fill the countries
import cartopy
import cartopy.crs as ccrs
import matplotlib.pyplot as plt
import cartopy.io.shapereader as shpreader

flag = "italy.png" #this is a locally saved png.

plt.figure(figsize=(15, 15)) #size of plot
ax = plt.axes(projection=cartopy.crs.TransverseMercator(25))
ax.add_feature(cartopy.feature.BORDERS, linestyle='-', alpha=1)
ax.coastlines(resolution='110m') #simplifies the border lines
ax.add_feature(cartopy.feature.OCEAN, facecolor="#40e0d0") #colour of ocean
# ax.gridlines() #adds global grid lines
ax.set_extent ((-7.5, 50, 34, 69), cartopy.crs.PlateCarree()) #makes it european


shpfilename = shpreader.natural_earth(resolution='110m',
                                      category='cultural',
                                      name='admin_0_countries')

for country in shpreader.Reader(shpfilename).records():
    if country.attributes['NAME_LONG'] == "Italy":
        ax.add_geometries(country.geometry, ccrs.PlateCarree(),
                          facecolor="blue",
                          #no attribute like this img= "fd",

                          label=country.attributes['NAME_LONG'])

plt.show()

Any help, much appreciated!

FYI. For a new user, you can't vote up my answer until you gain 25? reputation points. But you can mark it “accepted”, and earn "+2" reputation. https://stackoverflow.com/help/someone-answers — swatchai, Nov 23 '20 at 07:20

swatchai · Accepted Answer · 2020-11-21T01:22:47.043

Here is a demo code that does what you need. As a matter of fact, cartopy logo uses this technique to create.

import cartopy
import cartopy.crs as ccrs
import matplotlib.pyplot as plt
import cartopy.io.shapereader as shpreader
import matplotlib.patches as mpatches
import numpy as np

imdat1 = plt.imread('flag-of-italy.jpg', format='jpg') # use your flag

plt.figure(figsize=(8, 8))
ax = plt.axes(projection=cartopy.crs.TransverseMercator(25))
ax.add_feature(cartopy.feature.BORDERS, linestyle='-', alpha=1)
ax.coastlines(resolution='110m')
ax.add_feature(cartopy.feature.OCEAN, facecolor="#40e0d0")
# ax.gridlines() #adds global grid lines
ax.set_extent ((-7.5, 50, 24, 69), cartopy.crs.PlateCarree())

shpfilename = shpreader.natural_earth(resolution='110m',
                                      category='cultural',
                                      name='admin_0_countries')

italy_ctry = None  #use this to grab italy's

for country in shpreader.Reader(shpfilename).records():
    if country.attributes['NAME_LONG'] == "Italy":
        italy_ctry = country
        ax.add_geometries(country.geometry, ccrs.PlateCarree(),
                          facecolor="none",
                          alpha=0.7,
                          zorder=2,
                          label=country.attributes['NAME_LONG'])

# create mpatch from `italy` geometry
cg = italy_ctry.geometry
cg2 = cg.simplify(0.02)

if cg2.geometryType()=='MultiPolygon':
    # if == `Polygon`, dont need to loop
    for ea in cg2.geoms:
        cg2xy = ea.exterior.xy  # tuple of (x,y)
        xys = []
        for ea in zip(cg2xy[0], cg2xy[1]):
            #print(ea[0],ea[1])
            xys.append([ea[0],ea[1]])

        # add a patch
        poly = mpatches.Polygon(xys, closed=True, ec='r', \
                                lw=2, fc='yellow', \
                                transform=ccrs.PlateCarree(), \
                                alpha=0.5, zorder=30)

        plate_carree_transform = ccrs.PlateCarree()._as_mpl_transform(ax)

        xtent1 = (6.519950, 17.122259, 35.783370, 47.962952)
        imdat2 = ax.imshow(imdat1, origin='upper', extent=xtent1, \
            transform=ccrs.PlateCarree(), \
            zorder=15, alpha=.9)

        ##imdat2 = ax.stock_img()  #for testing
        imdat2.set_clip_path(mpatches.Path(xys), transform=plate_carree_transform) 
    pass

plt.show()

The sample plot (varies with the flag in use):

appreciated. Where are you pulling the xtent1 values from for the overlay extent? If it were to be dynamic and say I replaced Italy with Spain surely these values would have to change too? thanks — Andrew, Nov 25 '20 at 18:02
@Andrew Each `country.geometry` provides coordinates that can be processed to get its LL and UR corners. I didn't do that in the code but read them on a map. It is a good question that you can post as a new question. — swatchai, Nov 25 '20 at 18:42
Thanks, LL and UR: lower left and upper right? I suspect other two are low right and up right? Just to confirm, what do you mean by read them on a map? How have you sourced these figures - from calculating them from the output of country.geometry? thanks I will ask this after confirmations — Andrew, Nov 26 '20 at 17:22
thanks, where did you get/how did you calculate the xtent1 figures though? was it from another answer or something similar? thanks — Andrew, Nov 26 '20 at 17:54
@Andrew For exact LL/UR (corners) boundary of Italy, you can use `cg.bounds` and get (lonmin,latmin,lonmax,latmax) in degrees. In my code, I use crude values of that. — swatchai, Nov 26 '20 at 18:25

Overlay/Fill country boundaries with image in

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