如何将R ggplot图形存储为html代码段 [英] How to store r ggplot graph as html code snippet

问题描述

我正在通过使用ggplotly()和htmltools函数(例如h3()和html())创建各种对象来创建html文档.然后，我将它们作为列表提交给htmltools::save_html()以创建一个html文件.

I am creating an html document by creating various objects with ggplotly() and htmltools functions like h3() and html(). Then I submit them as a list to htmltools::save_html() to create an html file.

我想直接将ggplot图表添加为图像，而不是附加所有杂乱无章的钟声.最后，我将创建一个自包含的html文件(无依赖项)，而内容丰富的工作会使该文件过大.

I would like to add ggplot charts directly as images, rather than attaching all the plotly bells and whistles. In the end, I will create a self-contained html file (no dependencies), and the plotly stuff would make that file excessively large.

是否存在一些将ggplot对象转换为html类型对象的函数?还是我必须将ggplot保存为.png文件，然后将.png文件读入我添加到save_html()函数列表中的某个对象中?

Is there some function that converts a ggplot object into some html-type object? Or do I have to save the ggplot as a .png file, then read the .png file into some object that I add to the list in the save_html() function?

我的R代码看起来像这样:

My R code looks something like this:

library("tidyverse")
library("plotly")
library("htmltools")

HTMLOut <- "c:/Users/MrMagoo/My.html")
df <- data.frame(x=1:25, y=c(1:25*1:25))

g7 <- ggplot(df,aes(x=x, y=y)) + geom_point()
p7 <- ggplotly(g7)  # I would like to use something other than ggplotly here. Just capturing the ggplot as an image would be fine.

# create other objects to add to the html file
t7 <- h2(id="graph7", "Title for graph #7")
d7 <- p("description of graph 7")

save_html(list(t7, p7, d7), HTMLOut)
# of course, the real code has many more objects in that list – more graphs, text, tables, etc.

我想用只显示g7的东西替换plotly对象(p7)，而不会在save_html函数中引起错误.

I would like to replace the plotly object (p7) with something that just presents g7 in a way that would not cause an error in the save_html function.

我曾经希望找到一个可以直接对ggplot对象进行 Base64编码的函数，但是看来我首先需要将ggplot对象输出为.png文件(或SVG，下方的Teng L)，然后对其进行base64编码.我希望有一种更直接的方法，但是我最终可能会这样做，例如 https://stackoverflow.com/a/33410766/3799203 ，以

I had hoped to find a function that could directly Base64 encode a ggplot object, but it seems that I first need to output the 'ggplot' object as a .png file (or SVG, per Teng L, below), then base64-encode it. I was hoping there was a more direct way, but I may end up doing that, as in https://stackoverflow.com/a/33410766/3799203 , ending it with

g7img <- "<img src=\"data:image/png;base64,(base64encode string)\""
g7img <- htmltools::html(g7img)

推荐答案

我最终生成了一个临时图像文件，然后在我称为encodeGraphic()的函数中进行了base64编码(从LukeA的帖子):

I ended up generating a temparory image file, then base64 encoding it, within a function I called encodeGraphic() (borrowing code from LukeA's post):

library(ggplot2)
library(RCurl)
library(htmltools)
encodeGraphic <- function(g) {
  png(tf1 <- tempfile(fileext = ".png"))  # Get an unused filename in the session's temporary directory, and open that file for .png structured output.
  print(g)  # Output a graphic to the file
  dev.off()  # Close the file.
  txt <- RCurl::base64Encode(readBin(tf1, "raw", file.info(tf1)[1, "size"]), "txt")  # Convert the graphic image to a base 64 encoded string.
  myImage <- htmltools::HTML(sprintf('<img src="data:image/png;base64,%s">', txt))  # Save the image as a markdown-friendly html object.
  return(myImage)
}

HTMLOut <- "~/TEST.html"   # Say where to save the html file.
g <- ggplot(mtcars, aes(x=gear,y=mpg,group=factor(am),color=factor(am))) + geom_line()  # Create some ggplot graph object
hg <- encodeGraphic(g)  # run the function that base64 encodes the graph
forHTML <- list(h1("My header"), p("Lead-in text about the graph"), hg)
save_html(forHTML, HTMLOut)  # output it to the html file.

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