如何使用ggplot2在R中制作具有透明背景的图形? [英] How to make graphics with transparent background in R using ggplot2?

问题描述

我需要将 ggplot2 图形从 R 输出到具有透明背景的 PNG 文件.基本的 R 图形一切正常，但 ggplot2 没有透明度:

I need to output ggplot2 graphics from R to PNG files with transparent background. Everything is ok with basic R graphics, but no transparency with ggplot2:

d <- rnorm(100) #generating random data

#this returns transparent png
png('tr_tst1.png',width=300,height=300,units="px",bg = "transparent")
boxplot(d)
dev.off()

df <- data.frame(y=d,x=1)
p <- ggplot(df) + stat_boxplot(aes(x = x,y=y)) 
p <- p + opts(
    panel.background = theme_rect(fill = "transparent",colour = NA), # or theme_blank()
    panel.grid.minor = theme_blank(), 
    panel.grid.major = theme_blank()
)
#returns white background
png('tr_tst2.png',width=300,height=300,units="px",bg = "transparent")
p
dev.off()

ggplot2 有没有什么办法可以得到透明背景?

推荐答案

更新了 theme() 函数、ggsave() 和图例背景的代码:

Updated with the theme() function, ggsave() and the code for the legend background:

df <- data.frame(y = d, x = 1, group = rep(c("gr1", "gr2"), 50))
p <- ggplot(df) +
  stat_boxplot(aes(x = x, y = y, color = group), 
               fill = "transparent" # for the inside of the boxplot
  ) 

最快的方法是使用rect，因为所有的矩形元素都继承自rect:

Fastest way is using using rect, as all the rectangle elements inherit from rect:

p <- p +
  theme(
        rect = element_rect(fill = "transparent") # all rectangles
      )
    p

更可控的方式是使用theme的选项:

More controlled way is to use options of theme:

p <- p +
  theme(
    panel.background = element_rect(fill = "transparent"), # bg of the panel
    plot.background = element_rect(fill = "transparent", color = NA), # bg of the plot
    panel.grid.major = element_blank(), # get rid of major grid
    panel.grid.minor = element_blank(), # get rid of minor grid
    legend.background = element_rect(fill = "transparent"), # get rid of legend bg
    legend.box.background = element_rect(fill = "transparent") # get rid of legend panel bg
  )
p

保存(最后一步很重要):

To save (this last step is important):

ggsave(p, filename = "tr_tst2.png",  bg = "transparent")

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