1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
|
% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/shinywrappers.R
\name{renderImage}
\alias{renderImage}
\title{Image file output}
\usage{
renderImage(
expr,
env = parent.frame(),
quoted = FALSE,
deleteFile,
outputArgs = list()
)
}
\arguments{
\item{expr}{An expression that returns a list.}
\item{env}{The parent environment for the reactive expression. By default,
this is the calling environment, the same as when defining an ordinary
non-reactive expression. If \code{expr} is a quosure and \code{quoted} is \code{TRUE},
then \code{env} is ignored.}
\item{quoted}{If it is \code{TRUE}, then the \code{\link[=quote]{quote()}}ed value of \code{expr}
will be used when \code{expr} is evaluated. If \code{expr} is a quosure and you
would like to use its expression as a value for \code{expr}, then you must set
\code{quoted} to \code{TRUE}.}
\item{deleteFile}{Should the file in \code{func()$src} be deleted after
it is sent to the client browser? Generally speaking, if the image is a
temp file generated within \code{func}, then this should be \code{TRUE};
if the image is not a temp file, this should be \code{FALSE}. (For backward
compatibility reasons, if this argument is missing, a warning will be
emitted, and if the file is in the temp directory it will be deleted. In
the future, this warning will become an error.)}
\item{outputArgs}{A list of arguments to be passed through to the implicit
call to \code{\link[=imageOutput]{imageOutput()}} when \code{renderImage} is used in an
interactive R Markdown document.}
}
\description{
Renders a reactive image that is suitable for assigning to an \code{output}
slot.
}
\details{
The expression \code{expr} must return a list containing the attributes for
the \code{img} object on the client web page. For the image to display,
properly, the list must have at least one entry, \code{src}, which is the
path to the image file. It may also useful to have a \code{contentType}
entry specifying the MIME type of the image. If one is not provided,
\code{renderImage} will try to autodetect the type, based on the file
extension.
Other elements such as \code{width}, \code{height}, \code{class}, and
\code{alt}, can also be added to the list, and they will be used as
attributes in the \code{img} object.
The corresponding HTML output tag should be \code{div} or \code{img} and have
the CSS class name \code{shiny-image-output}.
}
\examples{
## Only run examples in interactive R sessions
if (interactive()) {
options(device.ask.default = FALSE)
ui <- fluidPage(
sliderInput("n", "Number of observations", 2, 1000, 500),
plotOutput("plot1"),
plotOutput("plot2"),
plotOutput("plot3")
)
server <- function(input, output, session) {
# A plot of fixed size
output$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 <- session$clientData$output_plot2_width
height <- session$clientData$output_plot2_height
# A temp file to save the output.
outfile <- tempfile(fileext='.png')
png(outfile, width=width, height=height)
hist(rnorm(input$n))
dev.off()
# Return a list containing the filename
list(src = outfile,
width = width,
height = height,
alt = "This is alternate text")
}, deleteFile = TRUE)
# Send a pre-rendered image, and don't delete the image after sending it
# NOTE: For this example to work, it would require files in a subdirectory
# named images/
output$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)
}
shinyApp(ui, server)
}
}
\seealso{
For more details on how the images are generated, and how to control
the output, see \code{\link[=plotPNG]{plotPNG()}}.
}
|
