transparent.colors: Function to provide the color code of a transparent color

In jacobmaugoust/ULT: Useful Little Things

Function to provide the color code of a transparent color

Description

This function gives the color code (either the name or the RGB code of the color) of a color given its transparency, with or without a specified background. It can also give the color codes of two colors given their transparency, with or without specified background, and of both transparent colors superimposed. This function is particularily useful to plot transparent colors and to use their "real" transparent value to use in a legend.

Usage

transparent.colors(front_color, back_color=NA,
                   front_alpha, back_alpha=NA,whole_background=NA,
                   output, simple_multicol_output=TRUE)

Arguments

front_color	The color (without alpha value) to be transparent over the background. Can be a name, a RGB code, and RGB values (between 0 and 1, 0 and 100 or 0 and 255).
back_color	The color (without alpha value) to be transparent under the front color and over the background. Can be a name, a RGB code, and RGB values (between 0 and 1, 0 and 100 or 0 and 255). Optional.
front_alpha	The transparency (or alpha value) of the front color. Can be between 0 and 1 and 0 and 100.
back_alpha	The transparency (or alpha value) of the back color. Can be between 0 and 1 and 0 and 100. Optional.
whole_background	The background color to be under the front color and potentially the back color. Cannot be transparent. By default, set to white.
output	The output of the color code(s). Can be "color name" (default value), being the color code in R, a "RGB 255 code" (values between 0 and 255) or a "RGB % code" (values between 0 and 1).
simple_multicol_output	Logical. The output of the function if you specify a front and a back colors. Set by default to TRUE, meaning the only output will be the "mixed" color. Otherwise, it will return a list of two elements containing (1) the front, back and mixed colors and (2) the mixed transparency.

Details

The function can return the color code of a single color with a given transparency and a given background. It can also return the color code of two colors with each a given transparency, and a given background. In this case, it can also return the transparency of the two colors superimposed.

Value

If there is a single color to be transparent, the color code or name. If there are two colors to be transparent, returns a list: the first element will contain the color codes or names, the second will return the transparency of the two colors superimposed. The output of this function can be used in a plot (or such) function to define a color (see example).

Examples

# For a single color to be transparent
random_alpha_value<-runif(1,0,1)
random_color<-rgb(red=runif(1,0,1),green=runif(1,0,1),blue=runif(1,0,1),alpha=random_alpha_value)
plot(1:1,type="n")
points(1,1,cex=20,pch=21,col=NA,bg=random_color)
transparent.colors(front_color=random_color,front_alpha=random_alpha_value, output="RGB 255 code")
# The returning RGB code corresponds to the color in the plot.
# For two colors overlapping
random_alpha_value<-runif(1,0,1)
random_colors<-c()
for(i in 1:2){random_colors<-c(random_colors,rgb(red=runif(1,0,1),green=runif(1,0,1),blue=runif(1,0,1),alpha=random_alpha_value))}
plot(1:8,1:8,type="n")
points(4:5,4:5,cex=20,pch=21,col=NA,bg=random_colors)
# The code for all colors
transparent.colors(front_color=random_colors,front_alpha=random_alpha_value,output = "RGB 255 code",simple_multicol_output = FALSE)
# For several colors successively overlapping
random_alpha_value<-runif(1,0,1)
random_colors<-c()
for(i in 1:5){random_colors<-c(random_colors,rgb(red=runif(1,0,1),green=runif(1,0,1),blue=runif(1,0,1),alpha=random_alpha_value))}
dev.new(width=8.958333,height=6.479167,unit="in",noRStudioGD = TRUE)
plot(1:1,1:1,type="n")
for(i in 1:5){points((1+(i-1)/15),1,cex=c(60-8*i),pch=21,col=NA,bg=random_colors[i])}
only_colors<-matrix(nrow=3,ncol=0,NA)
superimposed_colors<-matrix(nrow=3,ncol=0,NA)
for(i in 1:5){
  only_colors<-cbind(only_colors,transparent.colors(front_color = random_colors[i],front_alpha=random_alpha_value,output="RGB 255 code"))
  if(i>1){
    superimposed_colors<-cbind(superimposed_colors,transparent.colors(front_color=random_colors[i],front_alpha=random_alpha_value,back_color=rgb(t(superimposed_colors[,i-1]/255)),back_alpha = 1,output="RGB 255 code"))
  }
  else{
    superimposed_colors<-cbind(superimposed_colors,only_colors[,1])
  }
}
# Each transparent color (visible on the top right of each circle, on the top of the first one and the right side of the last one)
only_colors
# Each successive superimposed color (the aggregation of all colors)
superimposed_colors
# Demonstrating the interest of transparent.colors, especially while dealing with superimposed transparent colors one has to legend
cols<-c("black","gray10","gray20","gray30","gray40","gray50","gray60","pink","magenta","red")
alpha<-0.2
new_cols<-character(length=10)
new_cols[10]<-transparent.colors(front_color = cols[10],front_alpha=alpha)
for(i in 9:1){
  new_cols[i]<-transparent.colors(front_color=cols[i],front_alpha=alpha,back_color=new_cols[i+1],back_alpha=1)
}
par(mfrow=c(1,2))
plot(1:10,1:10,type="n",main="using 'transparent.colors'",axes=FALSE,bty="n",xlab="",ylab="")
for (i in 10:1){
  polygon(c(1,1:10,10),c(1,seq(from=(5+i/2),to=4,length.out = 10),1),col=new_cols[i],border=NA)
}
legend("topright",legend=letters[1:10],pch=21,pt.cex=1.5,col=NA,pt.bg=new_cols,text.col="black",bty="n")
plot(1:10,1:10,type="n",main="using 'alpha' in the plot, not\nbeing able to correct this in the legend",axes=FALSE,bty="n",xlab="",ylab="")
for (i in 10:1){
  polygon(c(1,1:10,10),c(1,seq(from=(5+i/2),to=4,length.out = 10),1),col=scales::alpha(cols[i],alpha),border=NA)
}
legend("topright",legend=letters[1:10],pch=21,pt.cex=1.5,col=NA,pt.bg=cols,text.col="black",bty="n")

jacobmaugoust/ULT documentation built on May 16, 2023, 1:29 p.m.