Save plotly plots to PNG file automatically

[dividor]

I am using plotly, but would like to automatically generate an image PNG file for the same plot. 

I am aware that we can call plotly_IMAGE, but this requires a call out to plotly servers which I want to avoid.

I optimistically tried putting my plot_ly call within a renderImage just to test, but it didn't work of course. Below is sample code.

Is there a way to do this please?

thanks!

ui.R

library(shiny)

library(plotly)

library(ggplot2movies)  # Needed for the 'movies' data set

shinyUI(fluidPage(

  titlePanel("Movie Ratings!"),

  sidebarPanel(

    sliderInput("bins", "Number of bins:", min = 1, max = 50, value = 10)

  ),

  mainPanel(

   # plotlyOutput("trendPlot"),

    imageOutput("myImage")

  )

))

server.R

Enter code here...minx <- min(movies$rating)

maxx <- max(movies$rating)

shinyServer(function(input, output) {

  

  output$trendPlot <- renderPlotly({

    # size of the bins depend on the input 'bins'

    size <- (maxx - minx) / input$bins

 

    # a simple histogram of movie ratings

    p <- plot_ly(movies, x = rating, autobinx = F, type = "histogram",

                 xbins = list(start = minx, end = maxx, size = size))

    

    # style the xaxis

    layout(p, xaxis = list(title = "Ratings", range = c(minx, maxx), autorange = F,

                           autotick = F, tick0 = minx, dtick = size))

    

  })

  

  output$myImage <- renderImage({

    # A temp file to save the output.

    # This file will be removed later by renderImage

    outfile <- 'output.png'

    

    # a simple histogram of movie ratings

    size <- (maxx - minx) / input$bins

    p <- plot_ly(movies, x = rating, autobinx = F, type = "histogram",

                 xbins = list(start = minx, end = maxx, size = size))

    # style the xaxis

    layout(p, xaxis = list(title = "Ratings", range = c(minx, maxx), autorange = F,

                           autotick = F, tick0 = minx, dtick = size))

    

    # Return a list containing the filename

    list(src = outfile,

         contentType = 'image/png',

         width = 400,

         height = 300,

         alt = "This is alternate text")

  }, deleteFile = FALSE)

  

  

})

[Joe Cheng]

I'm not sure but I've heard rumors that Yihui has the beginnings of a solution to this general problem...? :)

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[Yihui Xie]

Right. The webshot package makes this easy: https://github.com/wch/webshot

Here is a quick function that I wrote without any testing (I guess it
depends on the Github version of plotly since I'm using as.widget()
there):

#' @param x a plotly object
screenshot_plotly = function(x, file = 'webshot.png', ...) {
file2 = normalizePath(file, mustWork = FALSE)
d = tempfile()
dir.create(d)
owd = setwd(d)
on.exit({
setwd(owd)
unlink(d, recursive = TRUE)
}, add = TRUE)
htmlwidgets::saveWidget(plotly::as.widget(x), 'index.html', FALSE)
file.copy(webshot::webshot('index.html', ...), file2)
file
}

It returns the path of a screenshot of the plotly object, which I
believe you can pass as the image path to renderImage().

Regards,
Yihui

[dividor]

This seems very exciting!

Unfortunately though, my installation of Plotly gives me the error:

Error in : 'as.widget' is not an exported object from 'namespace:plotly'

Searching around on the web, I found this post which mentions downloading a dev version of plotly with ...

devtools::install_github("ropensci/plotly"

(having unloaded plotly first and restarted my session to bypass some namespace errors)

I then got a warning from webshot, telling me to install phantonjs by calling ..

webshot::install_phantomjs()

After all that, it worked perfectly!

My last question is though please - will as.widget be part of the standard plotly install at some point?

Thanks,

Matt

[Yihui Xie]

Yeah I did point out that as.widget() might require the Github version
of plotly, and you need to ask plotly developers when as.widget() will
be available in a CRAN release.

Regards,
Yihui

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[uap uap]

Ah, sorry I missed that part.

Thanks very much Yihui, this is an awesome feature.