Pixel image in R from character array

Question

I have generated a pixel-based image by encoding each input character to a certain color in the image. For example, in input txt <- "ABACDAAFFEDDADFAFAED" i plotted 'A' as a red pixel, 'B' as purple, 'C' by blue and 'D' by some other color. I used R for it. Here is the answer from where I have taken help for this Generate pixel based image in R from character array

Now, I want to update this for handling a case as well where I have a character presents 2 or three times consecutively and I want to give it a different color. For example txt <- "ABBACDAABBBEDDADCACABBDB", i want to give A- red, AA maroon, AAA dark red. B-green, BB- Pink, BBB-yellow, C-light brown, CC brown, CCC dark brown etc.

I still want to give 1 pixel to each char but for consecutive 2 or 3 appearances color those 2 or 3 pixels with a different color. I am unable to code a reasonable solution for it in R. Your help will be appreciated. Thanks

Answer 1

I changed the function to support multiple character :

library(png)
library(tiff)
library(abind)

# function which plots the image
createImage <- function(txt,charToColorMap,destinationFile,format=c('png','tiff'),debugPlot=FALSE,unused.char='#'){

  if(nchar(unused.char) != 1){
    stop('unused.char must be a single character, and you should be sure that it will never be present in your text')
  }



  # helper function which finds all the divisors of a number
  divisors <- function(x){
    y <- seq_len(x)
    y[ x%%y == 0 ]
  }

  # split the string in charaters
  chars <- strsplit(txt,'')[[1]]

  # find the most "squared" rectangle that contains all the characters without padding
  d <- divisors(length(chars)) 
  y <- d[length(d) %/% 2]
  x <- length(chars) / y

  # create an array with 4 matrices (or planes) one for each RGBA channel
  RGBAmx <- col2rgb(charToColorMap,alpha=TRUE) / 255
  colorIndexes <- match(chars,names(charToColorMap))

  ######################################
  # MULTIPLE CHAR
  ######################################
  # check if color map contains multiple character names
  multiple <- names(charToColorMap)[nchar(names(charToColorMap)) > 1]
  multiple <- multiple[order(nchar(multiple),decreasing=TRUE)]
  txtForMultiple <- txt
  for(m in multiple){
    idxs <- gregexpr(pattern=m,text=txtForMultiple,fixed=TRUE)[[1]]
    charRanges <- unlist(lapply(idxs,seq,length.out=nchar(m)))
    colorIndexes[charRanges] <- which(names(charToColorMap)==m)[1]
    tmp <- strsplit(txtForMultiple,'')[[1]]
    tmp[charRanges] <- unused.char
    txtForMultiple <- paste(tmp,collapse='')
  }
  #########################################################

  colorIndexesR <- matrix(RGBAmx['red',colorIndexes],nrow=y,ncol=x,byrow = TRUE)
  colorIndexesG <- matrix(RGBAmx['green',colorIndexes],nrow=y,ncol=x,byrow = TRUE)
  colorIndexesB <- matrix(RGBAmx['blue',colorIndexes],nrow=y,ncol=x,byrow = TRUE)
  colorIndexesA <- matrix(RGBAmx['alpha',colorIndexes],nrow=y,ncol=x,byrow = TRUE)

  planes <- abind(colorIndexesR,colorIndexesG,colorIndexesB,colorIndexesA,along=3)

  # write the PNG image
  if(format[1] == 'png'){
    writePNG(planes,destinationFile)
  }else if(format[1] == 'tiff'){
    writeTIFF(planes,destinationFile)
  }else{
    stop('usupported format')
  }

  # for debug purpose only we plot the image...
  if(debugPlot){
    mx <- matrix(colorIndexes,nrow=y,ncol=x,byrow = TRUE)
    image(z=t(mx[nrow(mx):1,]),col=charToColorMap)
  }

  invisible()
}

Usage example ('AAA' set to white) :

charToColorMap <- c(A='red',B='blue',C='green',D='black',E='yellow',F='orange',AAA='white')

txt <- "ABACAAAFFEDDADFAFAED"
# please note that unused.char will be used to mark the characters of txt already analyzed
# during the multi-char handling, so it must not be present in txt
createImage(txt,charToColorMap,destinationFile = "test.png",debugPlot=TRUE,unused.char='#')

Result (zoom 800 %):