Add A Large Shapefile To Map In Python Using Folium

January 15, 2024 Post a Comment

I am displaying a folium map in my application using python, PyQt5 and Qt designer. Since there is no map widget in Qt designer, I add a general widget and then promote it to my cu

Solution 1:

As already pointed out in these questions(1 and 2) and in the official docs:

void QWebEnginePage::setHtml(const QString &html, const QUrl &baseUrl = QUrl()) Sets the content of this page to html. baseUrl is optional and used to resolve relative URLs in the document, such as referenced images or stylesheets.
The html is loaded immediately; external objects are loaded asynchronously.
If a script in the html runs longer than the default script timeout (currently 10 seconds), for example due to being blocked by a modal JavaScript alert dialog, this method will return as soon as possible after the timeout and any subsequent html will be loaded asynchronously.
When using this method, the web engine assumes that external resources, such as JavaScript programs or style sheets, are encoded in UTF-8 unless otherwise specified. For example, the encoding of an external script can be specified through the charset attribute of the HTML script tag. It is also possible for the encoding to be specified by the web server.
This is a convenience function equivalent to setContent(html, "text/html", baseUrl).
Note: This method will not affect session or global history for the page.
Warning: This function works only for HTML, for other mime types (such as XHTML and SVG) setContent() should be used instead.
Warning: The content will be percent encoded before being sent to the renderer via IPC. This may increase its size. The maximum size of the percent encoded content is 2 megabytes minus 30 bytes.

_{(emphasis mine)}

setHtml() does not support content greater than 2MB, so in your particular case there are 2 solutions:

Baca Juga

Save the folium map in an html file:

import io
import os

from PyQt5 import QtCore, QtWidgets, QtWebEngineWidgets


CURRENT_DIR = os.path.dirname(os.path.realpath(__file__))


classLeafWidget(QtWidgets.QWidget):
    def__init__(self, parent=None):
        QtWidgets.QWidget.__init__(self, parent)

        self.view = QtWebEngineWidgets.QWebEngineView()

        shp_filename = os.path.join(CURRENT_DIR, "input", "2015_loaded_NoCC.shp")
        shp_file = gpd.read_file(shp_filename)
        shp_file_json_str = shp_file.to_json()

        m = folium.Map(location=[40, -120], zoom_start=10)
        folium.GeoJson(shp_file_json_str).add_to(m)

        tmp_file = QtCore.QTemporaryFile("XXXXXX.html", self)
        if tmp_file.open():
            m.save(tmp_file.fileName())
            url = QtCore.QUrl.fromLocalFile(tmp_file.fileName())
            self.view.load(url)

        lay = QtWidgets.QVBoxLayout(self)
        lay.addWidget(self.view)


defmain():
    app = QtWidgets.QApplication([])
    w = LeafWidget()
    w.show()
    app.exec_()


if __name__ == "__main__":
    main()

Use a QWebEngineUrlSchemeHandler to return the html:

qfolium.py

import json
import io

from PyQt5 import QtCore, QtWebEngineCore, QtWebEngineWidgets


classFoliumSchemeHandler(QtWebEngineCore.QWebEngineUrlSchemeHandler):
    def__init__(self, app):
        super().__init__(app)
        self.m_app = app

    defrequestStarted(self, request):
        url = request.requestUrl()
        name = url.host()
        m = self.m_app.process(name, url.query())
        if m isNone:
            request.fail(QtWebEngineCore.QWebEngineUrlRequestJob.UrlNotFound)
            return
        data = io.BytesIO()
        m.save(data, close_file=False)
        raw_html = data.getvalue()
        buf = QtCore.QBuffer(parent=self)
        request.destroyed.connect(buf.deleteLater)
        buf.open(QtCore.QIODevice.WriteOnly)
        buf.write(raw_html)
        buf.seek(0)
        buf.close()
        request.reply(b"text/html", buf)


classFoliumApplication(QtCore.QObject):
    scheme = b"folium"def__init__(self, parent=None):
        super().__init__(parent)
        scheme = QtWebEngineCore.QWebEngineUrlScheme(self.scheme)
        QtWebEngineCore.QWebEngineUrlScheme.registerScheme(scheme)
        self.m_functions = dict()

    definit_handler(self, profile=None):
        if profile isNone:
            profile = QtWebEngineWidgets.QWebEngineProfile.defaultProfile()
        handler = profile.urlSchemeHandler(self.scheme)
        if handler isnotNone:
            profile.removeUrlSchemeHandler(handler)

        self.m_handler = FoliumSchemeHandler(self)
        profile.installUrlSchemeHandler(self.scheme, self.m_handler)

    defregister(self, name):
        defdecorator(f):
            self.m_functions[name] = f
            return f

        return decorator

    defprocess(self, name, query):
        f = self.m_functions.get(name)
        if f isNone:
            print("not found")
            return

        items = QtCore.QUrlQuery(query).queryItems()
        params_json = dict(items).get("json", None)
        if params_json isnotNone:
            return f(**json.loads(params_json))
        return f()

    defcreate_url(self, name, params=None):
        url = QtCore.QUrl()
        url.setScheme(self.scheme.decode())
        url.setHost(name)
        if params isnotNone:
            params_json = json.dumps(params)
            query = QtCore.QUrlQuery()
            query.addQueryItem("json", params_json)
            url.setQuery(query)
        return url

main.py

import io
import os

import folium

from PyQt5 import QtCore, QtWidgets, QtWebEngineWidgets
import geopandas as gpd

from qfolium import FoliumApplication


CURRENT_DIR = os.path.dirname(os.path.realpath(__file__))

folium_app = FoliumApplication()


@folium_app.register("load_shapefile")defload_shapefile(latitude, longitude, zoom_start, shp_filename):
    shp_file = gpd.read_file(shp_filename)
    shp_file_json_str = shp_file.to_json()

    m = folium.Map(
        location=[latitude, longitude], zoom_start=zoom_start
    )
    folium.GeoJson(shp_file_json_str).add_to(m)
    print(m)
    return m


classLeafWidget(QtWidgets.QWidget):
    def__init__(self, parent=None):
        QtWidgets.QWidget.__init__(self, parent)

        self.view = QtWebEngineWidgets.QWebEngineView()

        lay = QtWidgets.QVBoxLayout(self)
        lay.addWidget(self.view)

        self.resize(640, 480)

        shp_filename = os.path.join(CURRENT_DIR, "input", "2015_loaded_NoCC.shp")

        params = {
            "shp_filename": shp_filename,
            "latitude": 40,
            "longitude": -120,
            "zoom_start": 5,
        }
        url = folium_app.create_url("load_shapefile", params=params)
        self.view.load(url)


defmain():
    app = QtWidgets.QApplication([])
    folium_app.init_handler()
    w = LeafWidget()
    w.show()
    app.exec_()


if __name__ == "__main__":
    main()

Python Manual

Add A Large Shapefile To Map In Python Using Folium

Solution 1:

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