add color alpha converter

color-alpha-converter/cac.clj

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+#!/usr/bin/env bb
+
+(require '[clojure.tools.cli :refer [parse-opts]])
+(use '[clojure.string])
+(require '[clojure.math :refer [round]])
+
+(def cli-options
+  [["-i" "--inverse" "Inverses the conversion so the value is converted to a percentage from a given hex number."
+    :id :inverse
+    :default false]])
+
+(def step-size 2.55M)
+(def parsed-params (parse-opts *command-line-args* cli-options))
+(def options (:options parsed-params))
+(def value (first (:arguments parsed-params)))
+
+(defn pad-with-zero
+  [length string]
+  (as-> string $
+   (count $)
+   (- length $)
+   (take $ (repeat "0"))
+   (concat $ string)
+   (join $)))
+
+(defn to-hex
+  [value]
+  (->> value
+      (Integer/parseInt)
+      (* step-size)
+      (round)
+      (int)
+      (format "%x")
+      (pad-with-zero 2)))
+
+(defn from-hex
+  [value]
+  (as-> value $
+      (Integer/parseInt $ 16)
+      (with-precision 2(/ $ step-size))
+      (round $)
+      (int $)
+      (str $)))
+
+(if (:inverse options)
+  (print (from-hex value))
+  (print (to-hex value)))

color-alpha-converter/readme.md

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+# Color Alpha Converter
+Converts the given alpha in percent to a hex value usable by Android.
+You can use the `-i` flag to inverse the conversion and get the alpha percentage for a hex value.
+
+## Example Usage
+```bash
+./cac.clj 50
+./cac.clj 80
+./cac.clj -i ff
+./cac.clj -i bf
+```