带有SF地图和替代性CR的背景图片

2024-06-01 • 问答

是否可以使用带有sf地图图的背景图像，并且还可以使用正在使用的坐标参考系统对图像进行转换？例如，下面的第一幅图使用NASA night lights image和EPSG：4326。第二个图像是EPSG：3035。数据点似乎已在CRS上正确绘制，但是背景图像未显示。

CRS EPSG 4326：似乎正确

CRS EPSG 3035：无背景图片

使用的代码：

# Download NASA night lights image
download.file("https://www.nasa.gov/specials/blackmarble/2016/globalmaps/
              BlackMarble_2016_01deg.jpg",destfile = "BlackMarble_2016_01deg.jpg",mode = "wb")

# Load picture and render
earth <- readJPEG("BlackMarble_2016_01deg.jpg",native = TRUE)
earth <- rasterGrob(earth,interpolate = TRUE)

# Select crs as desired
crs.inuse = 4326  # WGS 84
crs.inuse = 3035  # ETRS89 / LAEA Europe

# Plot geoname localities with population >100k with ggplot    
ggplot() +
  annotation_custom(earth,xmin = -180,xmax = 180,ymin = -90,ymax = 90) +
  geom_sf(data = popn.sf,aes(geometry=geometry),alpha = 0.4,size = 2,colour = "white") +
  theme(panel.background = element_rect(fill = "#05050f",colour = "#05050f"),panel.grid.major = element_blank(),panel.grid.minor = element_blank(),axis.title = element_blank(),axis.text = element_blank(),axis.ticks.length = unit(0,"cm"),legend.position = "none") +
  coord_sf(crs = st_crs(crs.inuse))

一种解决方法，将jpg文件作为RasterBrick导入并将其投影到所需的最终投影。最终图通过plot函数创建。我还绘制了海岸线，以便可以看到投影如何与RasterBrick一起工作。

您可以找到有关此技术here的进一步说明。

# Libraries----
library(sf)
library(raster)
library(rnaturalearth) #To get cities and coast to reprex

# Load shapefiles----
#popm.sf
popn.sf = ne_download(50,type = "populated_places",returnclass = "sf")
popn.sf_4326 = st_transform(popn.sf,4326)
popn.sf_3035 = st_transform(popn.sf_4326,3035)

#coasts
coast.sf = ne_download(10,category = "physical",type = "coastline",returnclass = "sf")
coast.sf_4326 = st_transform(coast.sf,4326)
coast.sf_3035 = st_transform(coast.sf,3035)


# Background----
# Download NASA night lights image
download.file(
  "https://www.nasa.gov/specials/blackmarble/2016/globalmaps/BlackMarble_2016_01deg.jpg",destfile = "BlackMarble_2016_01deg.jpg",mode = "wb"
)

#To brick
earth <- brick("BlackMarble_2016_01deg.jpg")
raster_4326 <- earth
projection(raster_4326) <-
  CRS(st_crs(popn.sf_4326)[["proj4string"]])
extent(raster_4326) <-
  c(-180,180,-89.99,89.99) # Sligth offset to 180,-90,90 to avoid errors

#Project raster
proj3035 <- st_crs(popn.sf_3035)[["proj4string"]]
raster_3035 = projectRaster(raster_4326,crs = proj3035) # Some warnings,but still working

#Extra: to plots----
png(
  "proj4326.png",bg = "#05050f",height = dim(raster_4326)[1],width = dim(raster_4326)[2]
)
par(mar = c(0,0))
plotRGB(raster_4326,bgalpha = 0)
plot(coast.sf_4326$geometry,col = "blue",add = T)
plot(
  popn.sf_4326$geometry,col = adjustcolor("white",alpha.f = .4),pch = 20,cex = 3,add = T
)
dev.off()

png(
  "proj3035.png",height = dim(raster_3035)[1],width = dim(raster_3035)[2]
)
par(mar = c(0,0))
plotRGB(raster_3035,bgalpha = 0)
plot(coast.sf_3035$geometry,add = T)
plot(
  popn.sf_3035$geometry,add = T
)
dev.off()

原始文件：

使用CRS 4326 ：

使用CRS 3035 ：

带有SF地图和替代性CR的背景图片

wujianlin1984 回答：带有SF地图和替代性CR的背景图片

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