Challenge 09-lolcat solution

challenges/09-lolcat/solutions/bytecommander/raincat1.py

@@ -0,0 +1,5 @@
+import sys
+h,s,v=0,1,1
+def R():H=h%360;C=v*s;M=v-C;X=int(255*(M+C*(1-abs((H/60)%2-1))));C=int((C+M)*255);return[[[[[(C,0,X),(X,0,C)][H<300],(0,X,C)][H<240],(0,C,X)][H<180],(X,C,0)][H<120],(C,X,0)][H<60]
+f=open(sys.argv[1])
+for l in f:print(end="\033[38;2;%d;%d;%dm%%s\033[0m"%R()%l);h+=10

challenges/09-lolcat/solutions/bytecommander/raincat2.py

@@ -0,0 +1,4 @@
+import sys
+def R(H):X=int(255*(1-abs((H/60)%2-1)));C=255;return[[[[[(C,0,X),(X,0,C)][H<300],(0,X,C)][H<240],(0,C,X)][H<180],(X,C,0)][H<120],(C,X,0)][H<60]
+i=0
+for l in open(*(sys.argv+[0])[1:2]):print("".join("\033[38;2;%d;%d;%dm"%R(h%360)+c for h,c in enumerate(l,i)),end="\033[0m");i+=8

challenges/09-lolcat/solutions/bytecommander/readme.md

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+# `raincat.py` by ByteCommander
+
+This script acts similar to `lolcat` as it prints its input to the terminal in a rainbow-colored way. 
+As the challenge includes code-golf, it is written as concise as possible, though surely further optimizations
+could still be made.
+
+It contains a HSV (Hue-Saturation-Value) to RGB (Red-Green-Blue) color conversion function inspired by 
+https://www.rapidtables.com/convert/color/hsv-to-rgb.html so that we can easily cycle through the hue degrees
+for a nice rainbow gradient.
+
+For coloring the output, we use ANSI escape codes to display 24-bit RGB colors,
+as described e.g. on https://stackoverflow.com/a/33206814/4464570.
+
+- The first version [`raincat1.py`](/challenges/09-lolcat/solutions/bytecommander/raincat1.py) 
+  only produced a plain vertical gradient and required exactly one input file path as command-line argument.
+  It contains the full color conversion formula that would accept varying Saturation and Value parameters,
+  but these are constantly 1 anyway.
+
+  ![raincat1.png](/challenges/09-lolcat/solutions/bytecommander/raincat1.png)
+
+- The second version [`raincat2.py`](/challenges/09-lolcat/solutions/bytecommander/raincat2.py)
+  creates a much finer, diagonal gradient by coloring each letter individually,
+  with a small hue delta per character and a slightly larger starting offset per line.
+  It also takes either one single file path as command-line argument (more arguments will be ignored)
+  or alternatively reads from stdin if none are given.
+  The conversion function has been simplified by removing the Saturation and Value parameters.
+
+  ![raincat2.png](/challenges/09-lolcat/solutions/bytecommander/raincat2.png)
+
+Tested and compatible with at least Python 3.5+ on Ubuntu, using gnome-terminal.