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matplotlib - 如何在特殊投影中的 cartopy 底图上绘制 png 图像？

问题描述

我正在尝试打开一个 png-Image 以将此图像绘制在 cartopy 的底图上。我已经按照以下说明操作： https ://scitools.org.uk/cartopy/docs/v0.15/examples/geostationary.html


import matplotlib.pyplot as plt
import cartopy.crs as ccrs
import cartopy
from PIL import Image



def create_map(image):

    res = '10m'
    proj = ccrs.NorthPolarStereo(central_longitude=10.0)
    img = plt.imread(image)
    img_extent = (2.0715, 15.72, 46.9526, 54.5877)

    ax = plt.axes(projection = proj)
    ax.set_extent = ([3.0889, 17.1128, 46.1827, 55.5482])    

    land_10m = cfeature.NaturalEarthFeature('physical', 'land', res,
                                         edgecolor = 'face', 
                                         facecolor=cfeature.COLORS['land'],
                                         zorder=0)

    state_provinces_10m = cfeature.NaturalEarthFeature(category = 'cultural', 
                                                       name = 'admin_1_states_provinces_lines',
                                                       scale = res,
                                                       facecolor = none)

    ax.add_feature(state_provinces_10m, edgecolor='gray')
    ax.add_feature(land_10m)
    ax.add_feature(cartopy.feature.BORDERS.with_scale(res), linestyle='-', linewith=1)
    ax.add_feature(cartopy.feature.COASTLINE.with_scale(res), linestyle='-')

    plt.imshow(img, origin='upper', extent=img_extent, transform = proj)

    plt.show()

create_map('image.png')

我的结果是定义范围的底图，但没有我的图像。我做错了什么？

问候

标签： matplotlibpython-3.7cartopy

解决方案

您的 transform 参数imshow几乎可以肯定是不正确的。北极立体投影中的影像范围(2.0715, 15.72, 46.9526, 54.5877)是靠近北极的一个非常小的区域，不在您想要的地图范围内。从上下文来看，范围似乎是在地理坐标中指定的，在这种情况下，应该transform=ccrs.PlateCarree()在您的imshow调用中使用解决方案。

一般来说，我建议始终明确说明您的坐标系是什么，所以我建议

def create_map(image):

    res = '10m'
    proj = ccrs.NorthPolarStereo(central_longitude=10.0)
    img = plt.imread(image)
    img_extent = (2.0715, 15.72, 46.9526, 54.5877)

    ax = plt.axes(projection = proj)
    # EXPLICIT CRS HERE:
    ax.set_extent([3.0889, 17.1128, 46.1827, 55.5482], crs=ccrs.PlateCarree())    

    land_10m = cfeature.NaturalEarthFeature('physical', 'land', res,
                                            edgecolor = 'face', 
                                            facecolor=cfeature.COLORS['land'],
                                            zorder=0)

    state_provinces_10m = cfeature.NaturalEarthFeature(category = 'cultural', 
                                                       name = 'admin_1_states_provinces_lines',
                                                       scale = res,
                                                       facecolor = none)

    ax.add_feature(state_provinces_10m, edgecolor='gray')
    ax.add_feature(land_10m)
    ax.add_feature(cartopy.feature.BORDERS.with_scale(res), linestyle='-', linewith=1)
    ax.add_feature(cartopy.feature.COASTLINE.with_scale(res), linestyle='-')

    # USE CORRECT CRS HERE
    plt.imshow(img, origin='upper', extent=img_extent, transform=ccrs.PlateCarree())

    plt.show()

本文档提供有关 Cartopy 中的转换/投影的指南： https ://scitools.org.uk/cartopy/docs/latest/tutorials/understanding_transform.html

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