如何通过命令行将Viewer Pane保存为图像？
假设我在查看器窗格中查看了以下HTML
tempDir <- tempfile()
dir.create(tempDir)
htmlFile <- file.path(tempDir, "index.html")
write('<h1> Content</h1>', htmlFile, append = TRUE)
write('<h2> Content</h2>', htmlFile, append = TRUE)
write('lorem ipsum...', htmlFile, append = TRUE)
viewer <- getOption("viewer")
viewer(htmlFile)
当我在查看器窗格中有这个html时,我可以点击"另存为图像"按钮:
我将html内容作为png,例如:
有没有办法用命令行执行此操作？我知道rstudioapi::savePlotAsImage(),所以我正在寻找一种saveViewerAsImage.
编辑:我知道我们可以使用{webshot}包来做到这一点,但我正在寻找能够做到这一点的RStudio函数.
RLe*_*sur 15
这是一个提案.策略如下:
- 让观众建立
png png从观众发送给R
让观众建立 png
甲canvas图像拥有.toDataURL()方法返回包含在该图像的表示的数据URI png格式(我们还可以得到一个jpeg格式).
该html2canvas库可用于截取屏幕截图:此库将当前页面呈现为canvas图像.
因此,可以在查看器中组合这两个函数:
- 截取屏幕截图
html2canvas - 将此屏幕截图转换为
png使用.toDataURL()
但是,该html2canvas库使用Promise(Windows版本)RStudio查看器不支持的JavaScript :需要填充填充.
将png观众发送给R
可以使用WebSockets实现此任务.
该httpuv包可用于创建Web服务器.此服务器将提供HTML将在RStudio查看器中打开的页面.
在httpuv服务器和RStudio查看器之间建立WebSocket通信.
从R命令行,可以向RStudio查看器发送WebSocket消息:接收此消息,查看器获取屏幕截图并将其发送回服务器.
代码
对不起,这段代码很长时间才能得到答案.
library(httpuv)
# Initialize variables
png <- NULL
websocket <- NULL
# Download Javascript libraries
polyfill_promise <- readLines('https://cdn.jsdelivr.net/npm/es6-promise/dist/es6-promise.auto.min.js')
html2canvas <- readLines('https://html2canvas.hertzen.com/dist/html2canvas.min.js')
# Configure the httpuv server
app <- list(
call = function(req) {
list(
status = 200L,
headers = list(
'Content-Type' = 'text/html'
),
body = paste0(collapse = "\r\n",
c("<!DOCTYPE html>",
"<html>",
"<head>",
# polyfill the RStudio viewer to support JavaScript promises
'<script type="text/javascript">',
polyfill_promise,
"</script>",
# use html2canvas library
'<script type="text/javascript">',
html2canvas,
"</script>",
"</head>",
"<body>",
html_body,
"</body>",
'<script type="text/javascript">',
# Configure the client-side websocket connection:
'var ws = new WebSocket("ws://" + location.host);',
# When a websocket message is received:
"ws.onmessage = function(event) {",
# Take a screenshot of the HTML body element
" html2canvas(document.body).then(function(canvas) {",
# Transform it to png
" var dataURL = canvas.toDataURL();",
# Send it back to the server
" ws.send(dataURL);",
" });",
"};",
"</script>",
"</html>"
)
)
)
},
# Configure the server-side websocket connection
onWSOpen = function(ws) {
# because we need to send websocket message from the R command line:
websocket <<- ws
# when a websocket message is received from the client
ws$onMessage(function(binary, message) {
png <<- message
})
}
)
# From your question:
html_body <- c(
'<h1> Content</h1>',
'<h2> Content</h2>',
'lorem ipsum...'
)
# Start the server:
server <- startDaemonizedServer("0.0.0.0", 9454, app)
# Open the RStudio viewer:
rstudioapi::viewer("http://localhost:9454")
# Wait to see the result...
# Send a websocket message from the command line:
websocket$send("go") # send any message
# Write the png image to disk:
writeBin(
RCurl::base64Decode(
gsub("data:image/png;base64,", "", png),
"raw"
),
"screenshot.png"
)
# Close the websocket connection
websocket$close()
# Stop the server
stopDaemonizedServer(server)
- 我觉得`wsUrl` 可能是`location.host`？ (2认同)
- @YihuiXie 好收获！由于这简化了答案，我已经更新了它。谢谢夸奖和赏金！ (2认同)