First upload

utils/textereo.awk

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+# Textereo: ASCII stereogram generator in AWK
+# Usage: [busybox] awk -f textereo.awk map.txt
+# Map format:
+# First line: [desired width] [maxpattern length]
+# Second line: alphabet (allowed characters to generate patterns from)
+# Next H lines: depth map, W digits from 0 to 7 without spaces
+# You can insert single zeros or empty lines into the map to adjust height
+#
+# Created by Luxferre in 2023, released into public domain
+
+function dchar(str, pos) { # delete a character from str at position pos
+  if(!pos) return str
+  else return substr(str, 1, pos - 1) substr(str, pos + 1)
+}
+
+function ichar(str, pos, c) { # insert a character c into str at position pos
+  return substr(str, 1, pos - 1) c substr(str, pos)
+}
+
+BEGIN { # we use 95-character subset from ASCII by default
+  "date +%N"|getline rseed;srand(rseed) # init the PRNG
+  getline # read the first line from the file to parse parameters
+  WIDTH = int($1) # desired width of the image to generate
+  PATLEN = int($2) # generated pattern length (must be between 8 and W/2)
+  getline # read the full character set
+  CHARSET = $0
+  CHRANGE = length(CHARSET)
+  if(WIDTH == 0) WIDTH = 78
+  if(PATLEN < 8 || PATLEN > (WIDTH/2)) PATLEN = 10 # 10 to 15 is optimal
+}
+
+{ # process the map itself
+  j = 0 # set the secondary counter to store previous value
+  FREEBUF = CHARSET # start with the full charset
+  PATBUF = "" # start with empty pattern buffer
+  mapline = $0 # cache the map line
+  RWIDTH = length(mapline); # real pattern width
+  tlen = (WIDTH - RWIDTH) / 2 # trailer AND header length
+  for(i=0;i<tlen;i++) mapline = "0" mapline "0" # grow the line to the width
+  if(length(mapline) > WIDTH) mapline = substr(mapline, 1, WIDTH)
+  for(i=0;i<PATLEN;i++) { # fill in the pattern buffer
+    do # we can repeat the characters in the pattern but not immediately
+      pbc = substr(CHARSET, 1+int(rand()*CHRANGE), 1)
+    while(pbc == j || !length(pbc)) # don't allow empty or repeating chars
+    PATBUF = PATBUF pbc # concatenate the character to the pattern
+    j = pbc # save as the previous value to j
+    # delete this character from the unused buffer
+    FREEBUF = dchar(FREEBUF, index(FREEBUF, pbc))
+  }
+  j = 0 # reset the secondary counter
+  prevlen = PATLEN # cache the previous pattern length
+  maplen = length(mapline)
+  patpos = 0 # track pattern position
+  for(i=0;++i<=maplen;) { # iterate over every character
+    curlen = PATLEN - int(substr(mapline, i, 1)) # extract depth value and length
+    delta = curlen - prevlen
+    if(delta > 0) # add unused characters if decreasing depth value
+      for(j=0;j<delta;j++) {
+        ri = 1+int(rand()*length(FREEBUF)) # get random index
+        rc = substr(FREEBUF, ri, 1) # retrieve the character
+        FREEBUF = dchar(FREEBUF, ri) # delete it from the buffer
+        PATBUF = ichar(PATBUF, 1+patpos, rc) # insert it here
+      }
+    else if(delta < 0) # remove characters if increasing depth value
+      for(j=0;j<-delta;j++)
+        PATBUF = dchar(PATBUF, 1+patpos)
+    prevlen = curlen # update the previous length
+    # now, output the current pattern character
+    printf("%c", substr(PATBUF, 1 + (patpos % curlen), 1))
+    patpos = (patpos + 1) % curlen # update pattern position
+  }
+  printf("\n")
+}