The renderImage() and imageOutput() functions can be used to display any image files on the client. This is in contrast to the renderPlot() and plotOutput() functions, which are used for images created by R's usual plot rendering device.
In the upper image, image1, a new image file is created each time the slider changes, and the deleteFile=TRUE argument tells the server to delete the temporary iamge file after it's sent to the client.
This technique can be also used for pre-rendered images. The lower image, image2 sends pre-rendered images to the client. In this case the deleteFile=FALSE argument is used so that the image files aren't deleted after being sent to the client.