How to save ggrough chart as .png

问题

Say that I am using the R package ggrough (https://xvrdm.github.io/ggrough/). I have this code (taken from that webpage):

library(ggplot2)
library(ggrough)
count(mtcars, carb) %>%
    ggplot(aes(carb, n)) +
    geom_col() + 
    labs(title="Number of cars by carburator count") + 
    theme_grey(base_size = 16) -> p 
options <- list(
    Background=list(roughness=8),
    GeomCol=list(fill_style="zigzag", angle_noise=0.5, fill_weight=2))

I can then create the chart (I am using RStudio):

get_rough_chart(p, options)

However, what code can I use to save it as a .png file? I am trying:

png("ggrough.png")
get_rough_chart(p, options)
dev.off()

I also tried:

x11()
get_rough_chart(p, options)

But this doesn't work either (and even if it did render in the x11 window, I don't know how to then save that as a .png.

What should I do to save the ggrough plot as a .png?

回答1:

The ggrough plot is an htmlwidget at heart so I do not think typical image saving code will work.

As mentioned, you can save htmlwidgets to disk via htmlwidgets::saveWidget(rough_chart_object, "rough_chart.html"). This creates an html file with an html canvas element that is drawn on via embedded javascript. As you noticed, webshot::webshot() is not able to capture the image for some reason I too have yet to figure out.

Because the html file renders correctly in Chrome, I wrote up this RSelenium approach. However, RSelenium can be a pain to get running with all the inter-dependencies, and the image created via this approach may require post-processing. That is, because the plot does not fill the entire canvas element, the image contains a lot of undesirable white space.

But I will leave this approach here for others to think about.

library(dplyr)
library(ggplot2)
library(ggrough)
library(RSelenium)
library(htmlwidgets)

# make ggplot
count(mtcars, carb) %>%
  ggplot(aes(carb, n)) +
  geom_col() + 
  labs(title="Number of cars by carburator count") + 
  theme_grey(base_size = 16) -> gg_obj

# convert to rough chart
options <- list(
  Background=list(roughness=8),
  GeomCol=list(fill_style="zigzag", angle_noise=0.5, fill_weight=2))

rough_chart <- get_rough_chart(p = gg_obj, rough_user_options = options)

# save rough chart
saveWidget(rough_chart, "rough_chart.html")

# start selenium driver
rd <- remoteDriver(
  remoteServerAddr = "localhost", 
  port = 4444L,
  browserName = "chrome"
)

rd$open()

# navigate to saved rough chart file
rd$navigate(paste0("file:///", getwd(), "/rough_chart.html"))

# find canvas element and size
canvas_element <- rd$findElement("id", "canvas")
canvas_size <- canvas_element$getElementSize()

# zoom to chart size with padding
rd$setWindowSize(canvas_size$width + 2 * canvas_size$x, 
                 canvas_size$height + 2 * canvas_size$y)

# save as png
rd$screenshot(file = "rough_chart.png")

# close chrome
rd$close()

来源：https://stackoverflow.com/questions/56817353/how-to-save-ggrough-chart-as-png

标签

ggplot2

rstudio

png

x11