download-plot-on-button-click.R

library(shiny)
library(ggplot2)
ui <- function(request){
  tagList(
    h2("Click on the plot to download it"),
    tags$button(
      "Click here to download the plot", 
      onclick = 'var a = document.createElement("a"); a.href = $("#plop").find("img").attr("src"); a.download = "Image.png"; a.click(); '
    ),
    plotOutput("plop") 
  )
}
server <- function(
  input, 
  output, 
  session
){
  output$plop <- renderPlot({
    ggplot(mtcars,aes(gear, carb)) + 
      geom_point()
  })
}
shinyApp(ui, server)

download-plot-on-click.R

library(shiny)
library(ggplot2)
ui <- function(request){
  tagList(
    h2("Click on the plot to download it"),
    plotOutput("plop") %>% 
      tagAppendAttributes(
        onclick = 'var a = document.createElement("a"); a.href = $(this).find("img").attr("src"); a.download = "Image.png"; a.click(); '
      )
  )
}
server <- function(
  input, 
  output, 
  session
){
  output$plop <- renderPlot({
    ggplot(mtcars,aes(gear, carb)) + 
      geom_point()
  })
}
shinyApp(ui, server)