R图：有没有办法在文本标签周围绘制边框，阴影或缓冲区？

Question

我想在单色图形中的一条线上绘制标签。所以我需要在标签的每个字母上留下小的白色边框。

文本标签的矩形边框或背景无用，因为隐藏了大量绘制的数据。

有没有办法在R图中的文本标签周围放置边框，阴影或缓冲区？

编辑：

shadowtext <- function(x, y=NULL, labels, col='white', bg='black',
                   theta= seq(pi/4, 2*pi, length.out=8), r=0.1, ... ) {

  xy <- xy.coords(x,y)
  xo <- r*strwidth('x')
  yo <- r*strheight('x')

  for (i in theta) {
    text( xy$x + cos(i)*xo, xy$y + sin(i)*yo, labels, col=bg, ... )
  }
  text(xy$x, xy$y, labels, col=col, ... )
}

pdf(file="test.pdf", width=2, height=2); par(mar=c(0,0,0,0)+.1)
  plot(c(0,1), c(0,1), type="l", lwd=20, axes=FALSE, xlab="", ylab="")
  text(1/6, 1/6, "Test 1")
  text(2/6, 2/6, "Test 2", col="white")
  shadowtext(3/6, 3/6, "Test 3")
  shadowtext(4/6, 4/6, "Test 4", col="black", bg="white")
  shadowtext(5/6, 5/6, "Test 5", col="black", bg="white", theta = seq(pi/4, 2*pi, length.out=24))
dev.off()

上面的代码使用了koekenbakker的解决方案。这适用于PNG图形，但我需要一种不同的高分辨率PDF方法。

Answer 1

您可以尝试这种'shadowtext'功能，通过多次打印以不同颜色的轻微偏移打印文本周围的光晕或边框。所有学分到Greg Snow here。

shadowtext <- function(x, y=NULL, labels, col='white', bg='black', 
                       theta= seq(0, 2*pi, length.out=50), r=0.1, ... ) {

    xy <- xy.coords(x,y)
    xo <- r*strwidth('A')
    yo <- r*strheight('A')

    # draw background text with small shift in x and y in background colour
    for (i in theta) {
        text( xy$x + cos(i)*xo, xy$y + sin(i)*yo, labels, col=bg, ... )
    }
    # draw actual text in exact xy position in foreground colour
    text(xy$x, xy$y, labels, col=col, ... )
}

# And here is an example of use:
# pdf(file="test2.pdf", width=2, height=2); par(mar=c(0,0,0,0)+.1)
plot(c(0,1), c(0,1), type="n", lwd=20, axes=FALSE, xlab="", ylab="")

rect(xleft = 0.5, xright = 1, ybottom = 0, ytop = 1, col=1)
text(1/6, 1/6, "Test 1")
shadowtext(2/6, 2/6, "Test 2", col='red', bg="blue")
shadowtext(3/6, 3/6, "Test 3", cex=2)

# `r` controls the width of the border
shadowtext(5/6, 5/6, "Test 4", col="black", bg="white", cex=4, r=0.2)
# dev.off()

Answer 2

我需要为R中的地图执行此操作，最后使用“raster”包在文本标签周围绘制光晕。

http://rpackages.ianhowson.com/cran/raster/man/text.html

EG，

library(raster)

text(Points, labels = Points$Labels, halo = TRUE, hw = 0.08, hc = "white", cex = 0.8)
# hw = halo width
# hc = halo color

Answer 3

shadowtext包可用于在ggplot2图的文本周围绘制轮廓或阴影。

library(ggplot2)
library(shadowtext)

jet.colors <- colorRampPalette(c("#00007F", "blue", "#007FFF", "cyan", "#7FFF7F", 
                                 "yellow", "#FF7F00", "red", "#7F0000"))

### Note: jet (rainbow) is not color-blind friendly, not perceptually uniform, and can be misleading 
# so please don't use it for your plots
# https://blogs.egu.eu/divisions/gd/2017/08/23/the-rainbow-colour-map/
# https://www.nature.com/articles/519291d
# Choose viridis instead https://cran.r-project.org/web/packages/viridis/vignettes/intro-to-viridis.html
# I only use jet here for the demonstration of the `shadowtext` package.

ggplot(faithfuld, aes(waiting, eruptions)) +
  geom_raster(aes(fill = density)) +
  scale_fill_gradientn(colors = jet.colors(7)) +
  geom_shadowtext(aes(x = 75, y = 4.5),
    label = "White text with black outline\nwill be visible on any background",
    check_overlap = TRUE,
    size = 8) +
  theme_minimal()

由reprex package创建于2018-10-14（v0.2.1.9000）

Answer 4

这是我在标记轮廓（或本例中的圆圈）时添加文本缓冲区的尝试。它绝对不像koekenbakker的解决方案那样有效或漂亮，但它的目的是让我将文本标签与行隔离开来。

require(shape)
plot(250,250, xlim=c(0,500), ylim=c(0,500), axes=F, ylab="", xlab="", col="black") ## set up the plotting area

circle_radius<-c(200, 150, 50) ## we wan't to draw a few circles which we will label after using our buffer

for (i in 1:length(circle_radius)){
    plotcircle(mid=c(250,250), r=circle_radius[i], lwd=0.5,lcol="grey40") ## iteratively plot the circles

text_buffer<-seq(0.1, 0.7, by=0.01) ## this is the key to the text buffer. Create a vector of values to set the character size (cex) during the following loop

for(j in text_buffer){
    text(x=250+circle_radius[i], 250, print(paste(circle_radius[i],"m")), cex=j, srt=270, col="white") ## write the text buffer in white starting from the smallest value of cex to the largest
}  ## end of loop for writing buffer
    text(x=250+circle_radius[i], 250, print(paste(circle_radius[i],"m")), cex=0.5, srt=270) ## write over the buffer with black text

}  ## end of loop for drawing circles

Answer 5

我为文本字段编写了一个类似的函数，它也适用于对数尺度。

install.packages("berryFunctions")
library("berryFunctions")
?textField

对于矢量图形，这可能被认为更好。这里有些例子：

PS：如果你想贡献：https://github.com/brry/berryFunctions