R：保存白色背景的传单答案

【问题标题】：R: saving a leaflet with white backgroundR：保存白色背景的传单
【发布时间】：2022-11-02 19:21:38
【问题描述】：

我目前正在开发一个 ShinyApp，其中包括使用 sf 对象和传单构建的地图。

我找到了将地图的初始灰色背景更改为白色背景（通过添加 css 样式）并将地图保存为 png（通过使用 webshot 或 mapshot）的解决方案。

然而，当我保存传单地图时，灰色背景又回来了！而且我没有找到用白色背景保存地图的解决方案。

这是说明我的问题的可重现代码：

# Libraries
library(shiny)
library(shinyWidgets)
library(htmlwidgets)
library(tidyr)
library(sf)
library(leaflet)
library(webshot)
library(mapview)

# Spatial data
d = matrix(c(0,0,10,0,10,10,0,10,0,0), ncol = 2, byrow = TRUE) %>%
  list(.) %>% st_polygon(.) %>% st_sfc(.)

# Shiny app
shinyApp(
  ui = shinyUI(fluidPage(tags$head(tags$style(HTML("#map{ background: none; }"))),
                         leafletOutput("map"),
                         downloadBttn("save", label = ".png"))),
  
  server = function(input, output){
    # Map creation
    map = reactiveVal(NULL)
    map(leaflet(d, options = leafletOptions()) %>% addPolygons())

    # Map render
    output$map = renderLeaflet(map())
    
    # Map download
    output$save = downloadHandler(
      file = function(){return("Rplot.png")},
      content = function(file){
        # Apply the changes user made (move and zoom)
        coords = input$map_center
        zoom = input$map_zoom
        shot = map() %>% setView(lng = coords$lng, lat = coords$lat, zoom = zoom)
        
        # Save the map unsing webshot (I prefer using this method for "heavy" map, like > 10 000 polygons)
        saveWidget(shot, "temp.html", selfcontained = FALSE)
        suppressWarnings({shot = webshot("temp.html", file = file, cliprect = "viewport")})
        
        # Save using mapshot
        # suppressWarnings({shot = mapshot(shot, file = file, cliprect = "viewport")})

        shot
      }
    )
  }
)

你有什么想法吗？

我尝试了不同的 css 背景样式（“none”、“white”、“#fff”）和不同的方式来保存传单地图（mapshot、webshot），但对我没有任何效果。

【问题讨论】：

标签： r shiny r-leaflet r-mapview

【解决方案1】：

我们可以使用leaflet.extras::setMapWidgetStyle来设置背景颜色：

# Libraries
library(shiny)
library(shinyWidgets)
library(htmlwidgets)
library(tidyr)
library(sf)
library(leaflet)
library(webshot)
library(mapview)
library(leaflet.extras)

# Spatial data
d = matrix(c(0,0,10,0,10,10,0,10,0,0), ncol = 2, byrow = TRUE) %>%
  list(.) %>% st_polygon(.) %>% st_sfc(.)

# Shiny app
shinyApp(
  ui = shinyUI(fluidPage(
    # tags$head(tags$style(HTML("#map{ background: none; }"))),
                         leafletOutput("map"),
                         downloadBttn("save", label = ".png"))),
  
  server = function(input, output){
    # Map creation
    map = reactiveVal(NULL)
    map(leaflet(d, options = leafletOptions()) %>% addPolygons() %>%
          setMapWidgetStyle(list(background = "white")))
    
    # Map render
    output$map = renderLeaflet(map())
    
    # Map download
    output$save = downloadHandler(
      file = function(){return("Rplot.png")},
      content = function(file){
        # Apply the changes user made (move and zoom)
        coords = input$map_center
        zoom = input$map_zoom
        shot = map() %>% setView(lng = coords$lng, lat = coords$lat, zoom = zoom)
        
        # Save the map unsing webshot (I prefer using this method for "heavy" map, like > 10 000 polygons)
        saveWidget(shot, "temp.html", selfcontained = FALSE)
        suppressWarnings({shot = webshot("temp.html", file = file, cliprect = "viewport")})
        
        # Save using mapshot
        # suppressWarnings({shot = mapshot(shot, file = file, cliprect = "viewport")})
        
        shot
      }
    )
  }
)

【讨论】：