通过 R Shiny 的 downloadHandler 下载 GeoTIFF 格式的多个光栅文件时出错

Question

我正在尝试制作一个基于 Shiny 的 Web 应用程序，它可以接受多个二进制文件作为用户的输入，并为每个输入文件创建一个 GeoTiff 光栅文件供用户下载。但是，我无法使用 R Shiny 的 DownloadHandler 将多个输出 GeoTiff 文件下载为 zip 文件夹。我尝试过的代码如下。

#Import required packages
library(shiny)
library(raster)
library(rgdal)
library(zip)
library(stringr)

#User Interface
ui = fluidPage(
titlePanel(title = "Convert Binary raster data to GeoTiff"),
sidebarLayout(position = "right",
sidebarPanel(
fileInput(inputId = "layer", label = "Upload your binary raster 
data", multiple = TRUE)
),
mainPanel(tableOutput("files"),
tableOutput("path"),
downloadButton(outputId = "downloadTiff", label = "Download GoeTiff 
file")
)
)
)
#Function to convert binary file to GeoTIFF raster data
bin_raster = function(x){
rf.file = file(x, 'rb')
bin_data = readBin(rf.file, what = 'double', n = 120705, size = 4, 
endian = "big")
rf_matrix = matrix(data = bin_data, nrow = 301, ncol = 401, byrow = 
T)
rf_rast1 = flip(raster(rf_matrix, xmn = 70, xmx = 110, ymn = 5, ymx = 
35,
crs = "+proj=longlat +datum=WGS84"), direction = 2)
return(rf_rast1)
}

#Server
server = function(input, output){

inFile = reactive({
if(is.null(input$layer$datapath)){return()}
else{
 for (i in input$layer$datapath) {
    wb = bin_raster(i)
    return(wb)
}
}

})

output$files = renderTable(input$layer)
output$path = renderTable(input$layer$datapath)

output$downloadTiff = downloadHandler(
filename = "GeoTiff.zip",
content = function(file){
#go to a temp dir to avoid permission issues
owd <- setwd(tempdir())
on.exit(setwd(owd))
files <- NULL;

for (i in 1:input$layer$datapath){

  fileName <- paste(input$layer$name,i,".tif",sep = "")
  writeRaster(inFile()$wb[i],fileName, format = "GTiff", overwrite = 
   TRUE)
  files <- c(fileName,files)
  }
#create the zip file
 zip(file,files)
 }
 )

 }

 shinyApp(ui = ui, server = server)

它向我显示以下错误： 1:input$layer$datapath 中的警告： 数值表达式有 2 个元素：仅使用第一个元素 download$func(tmpdata) 中的警告：强制引入的 NA 警告： :: NA/NaN 参数中的错误 [没有可用的堆栈跟踪]

请帮帮我。

Answer 1

这是一些运行的代码。

library(shiny)
library(raster)
library(rgdal)
library(zip)
library(stringr)

ui = fluidPage(
    titlePanel(title = "Convert Binary raster data to GeoTiff"),
    sidebarLayout(
        position = "right",
        sidebarPanel(
            fileInput(
                inputId = "layer",
                label = "Upload your binary raster data",
                multiple = TRUE
            )
        ),
        mainPanel(
            tableOutput("files"),
            tableOutput("path"),
            downloadButton(outputId = "downloadTiff", label = "Download GoeTiff file")
        )
    )
)

bin_raster = function(x) {
    rf.file = file(x, 'rb')
    bin_data = readBin(
        rf.file,
        what = 'double',
        n = 120705,
        size = 4,
        endian = "big"
    )
    rf_matrix = matrix(
        data = bin_data,
        nrow = 301,
        ncol = 401,
        byrow = T
    )
    rf_rast1 = flip(
        raster(
            rf_matrix,
            xmn = 70,
            xmx = 110,
            ymn = 5,
            ymx = 35,
            crs = "+proj=longlat +datum=WGS84"
        ),
        direction = 2
    )
    return(rf_rast1)
}

server = function(input, output) {
    inFile = reactive({
        if (is.null(input$layer$datapath)) {
            return()
        }
        else{
            for (i in input$layer$datapath) {
                wb = bin_raster(i)
                return(wb)
            }
        }
  })

    output$files = renderTable(input$layer)
    output$path = renderTable(input$layer$datapath)
    
    output$downloadTiff = downloadHandler(
        filename = "GeoTiff.zip",
        content = function(file) {
            #go to a temp dir to avoid permission issues
            owd <- setwd(tempdir())
            on.exit(setwd(owd))
            files <- NULL
            for (i in 1:length(input$layer$datapath)) {
                fileName <- paste(input$layer$name[i], ".tif", sep = "")
                rr <- bin_raster(input$layer$datapath[i])
                writeRaster(rr,
                                        fileName,
                                        format = "GTiff",
                                        overwrite = TRUE)
                files <- c(fileName, files)
            }
            #create the zip file
            zip::zip(file, files)
        }
    )
}

shinyApp(ui = ui, server = server)

我更改了以下内容

• for 循环必须使用输入的长度
• 必须读取每个文件并将其转换为光栅，因此我在写入gtiff 光栅之前调用了bin_raster。 inFile() 函数不起作用，因为它返回输入列表中的第一项，而不是所有项的列表。

读取栅格的代码会产生奇怪的结果，但我认为这是一个单独的问题。通常你会使用raster()，但如果栅格包含许多文件，这将不起作用。