{shinyscreenshot} has finally been released, two entire years (sorry!) after I began working on it. It allows you to capture screenshots of entire pages or parts of pages in Shiny apps, and have the image downloaded as a PNG automatically. It can be used to capture the current state of a Shiny app, including interactive widgets (such as plotly, timevis, maps, etc).

You can check out the demo to try it out yourself, or you can watch a short tutorial!

Table of contents

• How to use
• Screenshot button
• Features
• Installation
• Motivation
• Browser support and limitations
• Similar packages
• TWO YEARS?!

How to use

Using {shinyscreenshot} is as easy as it gets. When you want to take a screenshot, simply call screenshot() and a full-page screenshot will be taken and downloaded as a PNG image. Try it for yourself!

It’s so simple that an example isn’t needed, but here’s one anyway:

library(shiny)
library(shinyscreenshot)

ui <- fluidPage(
  textInput("text", "Enter some text", "test"),
  actionButton("go", "Take a screenshot")
)

server <- function(input, output) {
  observeEvent(input$go, {
    screenshot()
  })
}

shinyApp(ui, server)

Screenshot button

The screenshot() function can be called any time inside the server portion of a Shiny app. A very common case is to take a screenshot after clicking a button. That case is so common that there’s a function for it: screenshotButton(). It accepts all the same parameters as screenshot(), but instead of calling it in the server, you call it in the UI.

screenshotButton() creates a button that, when clicked, will take a screenshot.

Features

• Region: By default, the entire page is captured. If you’d like to capture a specific part of the screen, you can use the selector parameter to specify a CSS selector. For example, if you have a plot with ID myplot then you can use screenshot(selector="#myplot").

• Scale: The image file will have the same height and width as what is visible in the browser. Using screenshot(scale=2) will result in an image that’s twice the height and width (and also a larger file size).

• Timer: Usually you want the screenshot to be taken immediately, but sometimes you may want to tell Shiny to take a screenshot in, for example, 3 seconds from now. That can be done using screenshot(timer=3).

• File name: You can choose the name of the downloaded file using the filename parameter.

• Module support: As an alternative to the selector argument, you can also use the id argument. For example, instead of using screenshot(selector="#myplot"), you could use screenshot(id="myplot"). The advantage with using an ID directly is that the id parameter is module-aware, so even if you’re taking a screenshot inside a Shiny module, you don’t need to worry about namespacing.

Installation

To install the stable CRAN version:

install.packages("shinyscreenshot")

To install the latest development version from GitHub:

install.packages("remotes")
remotes::install_github("daattali/shinyscreenshot")

Motivation

For years, I saw people asking online how can they take screenshots of the current state of a Shiny app. This question comes up especially with interactive outputs (plotly, timevis, maps, DT, etc). Some of these don’t allow any way to save the current state as an image, and a few do have a “Save as image” option, but they only save the base/initial state of the output, rather than the current state after receiving user interaction.

After seeing many people asking about this, one day my R-friend Eric Nantz asked about it as well, which gave me the motivation to come up with a solution.

Browser support and limitations

The screenshots are powered by the ‘html2canvas’ JavaScript library. They do not always produce perfect screenshots, please refer to ‘html2canvas’ for more information about the limitations.

The JavaScript libraries used in this package may not be supported by all browsers. {shinyscreenshot} should work on Chrome, Firefox, Edge, Chrome on Android, Safari on iPhone (and probably more that I haven’t tested). It does not work in Internet Explorer.

Similar packages

As mentioned above, the libraries used by {shinyscreenshot} do have limitations and may not always work. There are two other packages that came out recently that also provide screenshot functionality which you may try and compare: {snapper} by Jonathan Sidi and {capture} by dreamRs.

RStudio’s {webshot} package is also similar, but serves a very different purpose. {webshot} is used to take screenshots of any website (including Shiny apps), but you cannot interact with the page in order to take a screenshot at a specific time.

TWO YEARS?!

Yes, I know. If you look at the commit history on GitHub, you’ll see this package started in 2018. I wrote almost the entire functionality of the package in just a few days, and then all I had left to do was the dreadful documentation. I didn’t want to release the package without great documentation, so I just waited until I’d have a free weekend to do that. But instead of coming back to do the documentation, I completely forgot about this package.

Many months later, COVID-19 hit us. One of my lockdown goals was to go through all my GitHub R packages and fix all the issues that I can. While doing that sweep, I noticed that I have this cool package that I forgot to release… If you really needed screenshots last year, then I apologize for this mistake. But, better late than never!

Lastly, if you enjoy my content, you should check out my new YouTube channel where I’ll be posting educational Shiny content!