mwhitaker/webshot

Take screenshots of web pages from R

webshot

Webshot makes it easy to take screenshots of web pages from R. It can also run Shiny applications locally and take screenshots of the app.

Installation

It requires an installation of the external program PhantomJS. Please make sure you have PhantomJS version 2 or higher installed. Previous versions may have trouble rendering some fonts. You may either download PhantomJS from its website, or use the function webshot::install_phantomjs() to install it automatically.

Once PhantomJS is installed you can install webshot with:

devtools::install_github("wch/webshot")

Usage

By default, webshot will use a 992x744 pixel viewport (a virtual browser window) and take a screenshot of the entire page, even the portion outside the viewport.

library(webshot)
webshot("https://www.r-project.org/", "r.png")
webshot("https://www.r-project.org/", "r.pdf") # Can also output to PDF

You can clip it to just the viewport region:

webshot("https://www.r-project.org/", "r-viewport.png", cliprect = "viewport")

You can also get screenshots of a portion of a web page using CSS selectors. If there are multiple matches for the CSS selector, it will use the first match.

webshot("https://www.r-project.org/", "r-sidebar.png", selector = ".sidebar")

If you supply multiple CSS selectors, it will take a screenshot containing all of the selected items.

webshot("https://www.r-project.org/", "r-selectors.png",
        selector = c("#getting-started", "#news"))

The clipping rectangle can be expanded to capture some area outside the selected items:

webshot("https://www.r-project.org/", "r-expand.png",
        selector = "#getting-started",
        expand = c(40, 20, 40, 20))

You can also change the user agent string, which is often used by sites to determine how to render. E.g. a mobile user string:

webshot("https://www.google.com", "mobile-useragent.png",
        userAgent="Mozilla/5.0 (iPhone; CPU iPhone OS 9_1 like Mac OS X)
        AppleWebKit/601.1.46 (KHTML, like Gecko) Version/9.0 Mobile/13B143 Safari/601.1")

Screenshots of Shiny applications

The appshot() function will run a Shiny app locally in a separate R process, and take a screenshot of it. After taking the screenshot, it will kill the R process that is running the Shiny app.

# Get the directory of one of the Shiny examples
appdir <- system.file("examples", "01_hello", package="shiny")
appshot(appdir, "01_hello.png")

Manipulating images

If you have GraphicsMagick (recommended) or ImageMagick installed, you can pass the result to resize() to resize the image after taking the screenshot. This can take any valid ImageMagick geometry specifictaion, like "75%", or "400x" (for an image 400 pixels wide).

You can also call shrink() function, which runs OptiPNG to shrink the PNG file losslessly.

webshot("http://www.google.com/", "google-small.png") %>%
 resize("75%") %>%
 shrink()

webshot("http://www.google.com/", "google-small.png") %>%
 resize("400x") %>%
 shrink()