Add a Legend with Images

Creates a legend with images that are embedded into a 'leaflet' map so that images do not need to be packaged when saving a 'leaflet' map as HTML. Full control over the label and title style. The 'leaflet' map is passed through and the output is a control so that legend is fully integrated with other functionalities.

addLegendImage(
  map,
  images,
  labels,
  title = "",
  labelStyle = "font-size: 24px; vertical-align: middle;",
  orientation = c("vertical", "horizontal"),
  width = 20,
  height = 20,
  group = NULL,
  className = "info legend leaflet-control",
  ...
)

Arguments

map	a map widget object created from 'leaflet'
images	path to the image file
labels	labels for each image
title	the legend title, pass in HTML to style
labelStyle	character string of style argument for HTML text
orientation	stack the legend items vertically or horizontally
width	in pixels
height	in pixels
group	group name of a leaflet layer group
className	extra CSS class to append to the control, space separated
...	arguments to pass to addControl

Value

an object from addControl

Examples

library(leaflet)
data(quakes)

quakes1 <- quakes[1:10,]

leafIcons <- icons(
  iconUrl = ifelse(quakes1$mag < 4.6,
                   "http://leafletjs.com/examples/custom-icons/leaf-green.png",
                   "http://leafletjs.com/examples/custom-icons/leaf-red.png"
  ),
  iconWidth = 38, iconHeight = 95,
  iconAnchorX = 22, iconAnchorY = 94,
  shadowUrl = "http://leafletjs.com/examples/custom-icons/leaf-shadow.png",
  shadowWidth = 50, shadowHeight = 64,
  shadowAnchorX = 4, shadowAnchorY = 62
)

leaflet(data = quakes1) %>% addTiles() %>%
  addMarkers(~long, ~lat, icon = leafIcons, group = 'Quake Leaves') %>%
  addLegendImage(images = c("http://leafletjs.com/examples/custom-icons/leaf-green.png",
                            "http://leafletjs.com/examples/custom-icons/leaf-red.png"),
                 labels = c('Green', 'Red'),width = 38, height = 95,
                 title = htmltools::tags$div('Leaf',
                 style = 'font-size: 24px; text-align: center;'),
                 position = 'topright',
                 group = 'Quake Leaves') %>%
  addLayersControl(overlayGroups = c('Quake Leaves'), position = 'bottomright')

 # use raster images with size encodings
 height <- sizeNumeric(quakes$depth, baseSize = 40)
 width <- height * 38 / 95
 symbols <- icons(
   iconUrl = 'http://leafletjs.com/examples/custom-icons/leaf-green.png',
   iconWidth = width,
   iconHeight = height)
 probs <- c(.2, .4, .6, .8)
 leaflet(quakes) %>%
   addTiles() %>%
   addMarkers(icon = symbols,
              lat = ~lat, lng = ~long) %>%
   addLegendImage(
     images = rep("http://leafletjs.com/examples/custom-icons/leaf-green.png", 4),
     labels = round(quantile(height, probs = probs), 0),
     width = quantile(height, probs = probs) * 38 / 95,
     height = quantile(height, probs = probs),
     title = htmltools::tags$div(
       'Leaf',
       style = 'font-size: 24px; text-align: center; margin-bottom: 5px;'),
     position = 'topright', orientation = 'vertical')