如何在 r 中的背景图像上方添加黑色覆盖半透明层？

Question

我在绘图中使用 背景图像 但绘图的颜色与图像混合，所以我想添加一个 覆盖半透明黑色将图层添加到背景图像 以便绘图颜色可以突出并且不与背景混合..

我试过添加 geom_rect() 但效果不佳 geom_rect(aes(xmin = min(date), xmax=max(date), ymin = -Inf, ymax=Inf), fill = "black", alpha = 0.3)

我怎样才能在整个背景图像上添加一个半透明的覆盖层。

结果失败

df

library(tidyverse)
library(lubridate)
library(ggpubr)
library(grid)
library(jpeg)

file_url1 <- "https://raw.githubusercontent.com/johnsnow09/covid19-df_stack-code/main/ts_all_long4.csv"

ts_all_long <- read.csv(url(file_url1))

ts_all_long <- ts_all_long %>%
  mutate(date = as.Date(date))

使用的图像：https://github.com/johnsnow09/covid19-df_stack-code/blob/a00c8820363f2163837d24f801f7c5b85167e0aa/coronavirus-4972480_1920.jpg

没有geom_rect():

ts_all_long %>% 
  filter(Country.Region == "Brazil") %>% 
  
  ggplot(aes(x = date, y = Confirmed_daily)) +
  background_image(readJPEG("Covid 19 images/coronavirus-4972480_1920.jpg")) +
  geom_area(size = 1, col = "#f08080", fill = "#f08080", alpha = 0.5)

与 geom_rect():

ts_all_long %>% 
  filter(Country.Region == "Brazil") %>% 
  
  ggplot(aes(x = date, y = Confirmed_daily)) +
  background_image(readJPEG("Covid 19 images/coronavirus-4972480_1920.jpg")) +
  geom_rect(aes(xmin = min(date), xmax=max(date), ymin = -Inf, ymax=Inf),
            fill = "black", alpha = 0.3) +
  geom_area(size = 1, col = "#f08080", fill = "#f08080", alpha = 0.5)

Answer 1

基于 this answer 我尝试了 annotate() 而不是 geom_rect()，这就成功了：

ts_all_long %>% 
  filter(Country.Region == "Brazil") %>% 
  
  ggplot(aes(x = date, y = Confirmed_daily)) +
  background_image(readJPEG("/home/johannes/Downloads/coronavirus-4972480_1920.jpg")) +
  annotate("rect", xmin = min(ts_all_long$date), xmax = max(ts_all_long$date), ymin = -Inf, ymax = Inf,
            fill = "black", alpha = 0.3) +
  geom_area(size = 1, col = "#f08080", fill = "#f08080", alpha = 0.5)

^{由 reprex package (v2.0.0)}

于 2021-04-20 创建

不过，我认为这样做实际上会更好看：

ts_all_long %>% 
  filter(Country.Region == "Brazil") %>% 
  
  ggplot(aes(x = date, y = Confirmed_daily)) +
  background_image(readJPEG("/home/johannes/Downloads/coronavirus-4972480_1920.jpg")) +
  geom_area(size = 1, col = "white", fill = "#f08080", alpha = 0.5)

^{由 reprex package (v2.0.0)}

于 2021-04-20 创建

如何在 r 中的背景图像上方添加黑色覆盖半透明层？

How to add a black overlay semi transparent layer above the background image in r?

r

ggplot2

background-image