fnd fnd - 3 months ago 23
R Question

R: Is there any way to put border, shadow or buffer around text labels en R plots?

I want to plot a label over a line in a monochrome graphic. So I need small white border on each letter of the label.

The border or background of rectangle of the text label is not usefull because hide a lot of data plotted.

Is there any way to put border, shadow or buffer around text labels en R plots?

EDIT:

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()


The code above use the solution from koekenbakker. This is fine for PNG graphics.

I need a different approach for high resolution o vector PDF like this https://docs.google.com/file/d/0BwpJogoN4kzHUEkwMEI2Rzg2T0k/edit?pli=1

Answer

You can try this shadowtext function that draws a halo or border around the text by drawing it several times at 8 slightly different positions in a different colour. All credits to 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()

enter image description here