从闪亮的应用程序中下载后，plotly图的图像已损坏

Question

下面有一个闪亮的应用程序，我想在其中使用downloadhandler()下载一个绘图。但是，正如您将看到的，当我在Web浏览器中运行该应用程序并下载图像时，直方图的下部丢失了。为什么会这样？可以修复此问题还是可以替代下载？如果您想知道为什么我对下载按钮和电影数据集使用了uiOutput()，那是因为这就是我原来更复杂的应用程序的工作方式。开始之前：

 library(webshot)
 install_phantomjs()


#uir.r
library(shiny)
library(plotly)
library(ggplot2movies) # movies is no longer contained within ggplot2 https://cran.r-project.org/web/packages/ggplot2movies/index.html

shinyUI(fluidPage(
  titlePanel("Movie Ratings!"),
  sidebarPanel(
    uiOutput("down")
  ),
  mainPanel(
    plotlyOutput("trendPlot")
  )
))
#server.r
library(shiny)
library(plotly)
library(ggplot2movies) # movies is no longer contained within ggplot2 https://cran.r-project.org/web/packages/ggplot2movies/index.html

shinyServer(function(input, output) {


  output$down<-renderUI({
    output$downloadData <- downloadHandler(
      filename = function(){

        paste0(paste0("pic"), ".png")
      },
      content = function(file) {
            export(reg(), file=file)
      }) 
    downloadButton("downloadData", "Download")
  })

  reg<-reactive({
    movies
    # Create axes titles as lists
    x <- list(
      title = "A",
      dtick = 5 
    )
    y <- list(
      title = "B"
    )
    # Create the plotly histogram

    plot_ly(alpha = 0.9) %>%
      add_histogram(x = as.factor(movies$rating)) %>%
      # Add titles in plot and axes
      layout(barmode = "overlay",title = "SAD",xaxis=x,yaxis=y)
  })
  output$trendPlot <- renderPlotly({
    reg()

  })
})

孤立的图像