How to use different fonts in an R Shiny plot

问题

I would like to create a plot in Shiny that the user can then download as a pdf using a custom font specified as a user input.

To be specific, I would like to use a pdf function such as pdf("plot.pdf", width = 5, height = 5, family = font.family), where the value of font.family is specified by the user.

Here is a simple example below: If I run the example on my machine, it works fine. However, when it is hosted on the RStudio shiny servers, I receive an error saying that the specified font family cannot be found. I think the problem is that the fonts I want are not accessible on the RStudio shiny servers, but is there a way I can include them?

server.R

shinyServer(function(input, output) {

output$distPlot <- renderPlot({

plot(1, xlim = c(0, 1), ylim = c(0, 1))
text(.5, .5, "Custom Font!!"
})

output$downloadPlot <- downloadHandler(

  filename = function() {paste('CustomFont.pdf')}, 
  content = function(file){

font.family <- input$font.family

pdf(file, width = 11, height= 8.5, family = font.family)

plot(1, xlim = c(0, 1), ylim = c(0, 1))
text(.5, .5, fonts(), cex = 10)


dev.off()
}, contentType = "image/pdf"
)
})

ui.R

 shinyUI(fluidPage(

 sidebarLayout(
 sidebarPanel(
  selectInput("font.family", "Choose Font", 
              choices = c("Helvetica Neue", "Times New Roman", "Arial")
  ),
  downloadButton("downloadPlot", "Download Plot as PDF")
),

# Show a plot of the plot
mainPanel(
  plotOutput("distPlot", width = "800px", height = "800px")
  ))))

回答1:

I had a similar problem. To solve that, much of the renderPlot() functionality was recreated using renderImage(), as described in this Shiny tutorial article. Font rendering then worked as desired.

This is the code which solved that question; it might also solve this one.

ui.R amend to

mainPanel(
  imageOutput("myImage")
)

server.R

shinyServer(function(input, output, session) {

  # A dynamically-sized plot
  output$myImage <- renderImage({
    # Read myImage's width and height. These are reactive values, so this
    # expression will re-run whenever they change.
    width  <- session$clientData$output_myImage_width
    height <- session$clientData$output_myImage_height

    # For high-res displays, this will be greater than 1
    pixelratio <- session$clientData$pixelratio

    # A temp file to save the output.
    outfile <- tempfile(fileext='.png')

    # Generate the image file
    png(outfile, width=width*pixelratio, height=height*pixelratio,
        res=72*pixelratio)
    plot(rnorm(100), rnorm(100), family="serif")
    dev.off()

    # Return a list containing the filename
    list(src = outfile,
         width = width,
         height = height,
         alt = "This is alternate text")
  }, deleteFile = TRUE) # delete the temp file when finished

})

来源：https://stackoverflow.com/questions/28034091/how-to-use-different-fonts-in-an-r-shiny-plot

标签

pdf

Shiny