renderImage {shiny} | R Documentation |
Renders a reactive image that is suitable for assigning to an output
slot.
renderImage(expr, env = parent.frame(), quoted = FALSE, deleteFile = TRUE)
expr |
An expression that returns a list. |
env |
The environment in which to evaluate |
quoted |
Is |
deleteFile |
Should the file in |
The expression expr
must return a list containing the attributes for
the img
object on the client web page. For the image to display,
properly, the list must have at least one entry, src
, which is the
path to the image file. It may also useful to have a contentType
entry specifying the MIME type of the image. If one is not provided,
renderImage
will try to autodetect the type, based on the file
extension.
Other elements such as width
, height
, class
, and
alt
, can also be added to the list, and they will be used as
attributes in the img
object.
The corresponding HTML output tag should be div
or img
and have
the CSS class name shiny-image-output
.
For more details on how the images are generated, and how to control
the output, see plotPNG
.
## Not run: shinyServer(function(input, output, clientData) { # A plot of fixed size output$plot1 <- renderImage({ # A temp file to save the output. It will be deleted after renderImage # sends it, because deleteFile=TRUE. outfile <- tempfile(fileext='.png') # Generate a png png(outfile, width=400, height=400) hist(rnorm(input$n)) dev.off() # Return a list list(src = outfile, alt = "This is alternate text") }, deleteFile = TRUE) # A dynamically-sized plot output$plot2 <- renderImage({ # Read plot2's width and height. These are reactive values, so this # expression will re-run whenever these values change. width <- clientData$output_plot2_width height <- clientData$output_plot2_height # A temp file to save the output. outfile <- tempfile(fileext='.png') png(outfile, width=width, height=height) hist(rnorm(input$obs)) dev.off() # Return a list containing the filename list(src = outfile, width = width, height = height, alt = "This is alternate text") }, deleteFile = TRUE) # Send a pre-rendered image, and don't delete the image after sending it output$plot3 <- renderImage({ # When input$n is 1, filename is ./images/image1.jpeg filename <- normalizePath(file.path('./images', paste('image', input$n, '.jpeg', sep=''))) # Return a list containing the filename list(src = filename) }, deleteFile = FALSE) }) ## End(Not run)