Take a screenshot of a URL

webshot(url = NULL, file = "webshot.png", vwidth = 992,
vheight = 744, cliprect = NULL, selector = NULL, expand = NULL,
delay = 0.2, zoom = 1, eval = NULL, debug = FALSE,
useragent = NULL)

## Arguments

url A vector of URLs to visit. A vector of names of output files. Should end with .png, .pdf, or .jpeg. If several screenshots have to be taken and only one filename is provided, then the function appends the index number of the screenshot to the file name. Viewport width. This is the width of the browser "window". Viewport height This is the height of the browser "window". Clipping rectangle. If cliprect and selector are both unspecified, the clipping rectangle will contain the entire page. This can be the string "viewport", in which case the clipping rectangle matches the viewport size, or it can be a four-element numeric vector specifying the top, left, width, and height. When taking screenshots of multiple URLs, this parameter can also be a list with same length as url with each element of the list being "viewport" or a four-elements numeric vector. This option is not compatible with selector. One or more CSS selectors specifying a DOM element to set the clipping rectangle to. The screenshot will contain these DOM elements. For a given selector, if it has more than one match, only the first one will be used. This option is not compatible with cliprect. When taking screenshots of multiple URLs, this parameter can also be a list with same length as url with each element of the list containing a vector of CSS selectors to use for the corresponding URL. A numeric vector specifying how many pixels to expand the clipping rectangle by. If one number, the rectangle will be expanded by that many pixels on all sides. If four numbers, they specify the top, right, bottom, and left, in that order. When taking screenshots of multiple URLs, this parameter can also be a list with same length as url with each element of the list containing a single number or four numbers to use for the corresponding URL. Time to wait before taking screenshot, in seconds. Sometimes a longer delay is needed for all assets to display properly. A number specifying the zoom factor. A zoom factor of 2 will result in twice as many pixels vertically and horizontally. Note that using 2 is not exactly the same as taking a screenshot on a HiDPI (Retina) device: it is like increasing the zoom to 200 doubling the height and width of the browser window. This differs from using a HiDPI device because some web pages load different, higher-resolution images when they know they will be displayed on a HiDPI device (but using zoom will not report that there is a HiDPI device). An optional string with JavaScript code which will be evaluated after opening the page and waiting for delay, but before calculating the clipping region and taking the screenshot. See the Casper API (http://docs.casperjs.org/en/latest/modules/casper.html) for more information about what commands can be used to control the web page. NOTE: This is experimental and likely to change! Print out debugging messages from PhantomJS and CasperJS. This can help to diagnose problems. The User-Agent header used to request the URL. Changing the User-Agent can mitigate rendering issues for some websites.

appshot for taking screenshots of Shiny applications.

## Examples

if (interactive()) {

# Whole web page
webshot("https://github.com/rstudio/shiny")

# Might need a longer delay for all assets to display
webshot("http://rstudio.github.io/leaflet", delay = 0.5)

# One can also take screenshots of several URLs with only one command.
# This is more efficient than calling 'webshot' multiple times.
webshot(c("https://github.com/rstudio/shiny",
"http://rstudio.github.io/leaflet"),
delay = 0.5)

# Clip to the viewport
webshot("http://rstudio.github.io/leaflet", "leaflet-viewport.png",
cliprect = "viewport")

# Manual clipping rectangle
webshot("http://rstudio.github.io/leaflet", "leaflet-clip.png",
cliprect = c(200, 5, 400, 300))

# Using CSS selectors to pick out regions
webshot("http://reddit.com/", "reddit-top.png",

# Expand selection region
webshot("http://rstudio.github.io/leaflet", "leaflet-boxes.png",
selector = "#installation", expand = c(10, 50, 0, 50))

# If multiple matches for a given selector, it uses the first match
webshot("http://rstudio.github.io/leaflet", "leaflet-p.png", selector = "p")
webshot("https://github.com/rstudio/shiny/", "shiny-stats.png",
selector = "ul.numbers-summary")

# Send commands to eval
webshot("http://www.reddit.com/", "reddit-input.png",
eval = "casper.then(function() {
// Check the remember me box

// Now click in the search box. This results in a box expanding below
this.click('#search input[type=\"text\"]');
// Wait 500ms
this.wait(500);
});"
)

# Result can be piped to other commands like resize() and shrink()
webshot("https://www.r-project.org/", "r-small.png") %>%
resize("75%") %>%
shrink()

# Requests can change the User-Agent header
webshot(
}