Add support for CSS three-letter color codes

Soft · Mar 25, 2018 · e6c77cb · e6c77cb
1 parent c34bb5d
commit e6c77cb
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Showing 3 changed files with 58 additions and 14 deletions.
diff --git a/README.md b/README.md
@@ -49,7 +49,7 @@ FLAGS:
 
 OPTIONS:
     -c, --custom <FORMAT>          Custom output format
-    -f, --format <NAME>            Output format (defaults to hex) [possible values: hex, HEX, plain, rgb]
+    -f, --format <NAME>            Output format (defaults to hex) [possible values: hex, HEX, hex!, HEX!, plain, rgb]
     -s, --selection <SELECTION>    Output to selection (defaults to primary) [possible values: primary, secondary]
 ```
 
@@ -70,12 +70,19 @@ By default, the color values will be printed in lowercase hexadecimal format.
 The output format can be changed using the `-f FORMAT` switch. The possible
 format values are listed bellow:
 
-| Format Specifier | Description                       | Example               | Custom Format Equivalent |
-| ---------------- | --------------------------------- | --------------------- | ------------------------ |
-| `hex`            | Lowercase hexadecimal (default)   | `#ff00ff`             | `#%{02hr}%{02hg}%{02hb}` |
-| `HEX`            | Uppercase hexadecimal             | `#00FF00`             | `#%{02Hr}%{02Hg}%{02Hb}` |
-| `rgb`            | Decimal RGB                       | `rgb(255, 255, 255)`  | `rgb(%{r}, %{g}, %{b})`  |
-| `plain`          | Decimal with semicolon separators | `0;0;0`               | `%{r};%{g};%{b}`         |
+| Format Specifier | Description                               | Example               | Custom Format Equivalent |
+| ---------------- | ---------------------------------         | --------------------- | ------------------------ |
+| `hex`            | Lowercase hexadecimal (default)           | `#ff00ff`             | `#%{02hr}%{02hg}%{02hb}` |
+| `HEX`            | Uppercase hexadecimal                     | `#00FF00`             | `#%{02Hr}%{02Hg}%{02Hb}` |
+| `hex!`           | Compact lowercase hexadecimal<sup>1</sup> | `#fff`                | Not expressible          |
+| `HEX!`           | Compact uppercase hexadecimal<sup>1</sup> | `#F0F`                | Not expressible          |
+| `rgb`            | Decimal RGB                               | `rgb(255, 255, 255)`  | `rgb(%{r}, %{g}, %{b})`  |
+| `plain`          | Decimal with semicolon separators         | `0;0;0`               | `%{r};%{g};%{b}`         |
+
+**1:** The compact form refers to CSS three-letter color codes as specified by [CSS
+Color Module Level 3](https://www.w3.org/TR/2018/PR-css-color-3-20180315/#rgb-color).
+If the color is not expressible in three-letter form, the regular six-letter
+form will be used.
 
 ### Custom Formatting
 

diff --git a/src/cli.rs b/src/cli.rs
@@ -11,7 +11,7 @@ pub fn get_cli() -> App<'static, 'static> {
              .takes_value(true)
              .value_name("NAME")
              .help("Output format (defaults to hex)")
-             .possible_values(&["hex", "HEX", "plain", "rgb"])
+             .possible_values(&["hex", "HEX", "hex!", "HEX!", "plain", "rgb"])
              .conflicts_with("custom"))
         .arg(Arg::with_name("custom")
              .short("c")

diff --git a/src/format.rs b/src/format.rs
@@ -137,9 +137,15 @@ impl FormatColor for FormatString {
 
 // Formatting Shortcuts
 
+#[derive(PartialEq)]
+pub enum HexCompaction {
+    Compact,
+    Full
+}
+
 pub enum Format {
-    LowercaseHex,
-    UppercaseHex,
+    LowercaseHex(HexCompaction),
+    UppercaseHex(HexCompaction),
     Plain,
     RGB
 }
@@ -148,20 +154,42 @@ impl FromStr for Format {
     type Err = Error;
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         match s {
-            "hex" => Ok(Format::LowercaseHex),
-            "HEX" => Ok(Format::UppercaseHex),
+            "hex" => Ok(Format::LowercaseHex(HexCompaction::Full)),
+            "HEX" => Ok(Format::UppercaseHex(HexCompaction::Full)),
+            "hex!" => Ok(Format::LowercaseHex(HexCompaction::Compact)),
+            "HEX!" => Ok(Format::UppercaseHex(HexCompaction::Compact)),
             "plain" => Ok(Format::Plain),
             "rgb" => Ok(Format::RGB),
             _ => Err(err_msg("Invalid format"))
         }
     }
 }
 
+
+fn is_compactable((r, g, b): RGB) -> bool {
+    fn compact(n: u8) -> bool {
+        (n >> 4) == (n & 0xf)
+    }
+    compact(r) && compact(g) && compact(b)
+}
+
 impl FormatColor for Format {
     fn format(&self, (r, g, b): RGB) -> String {
         match *self {
-            Format::LowercaseHex => format!("#{:02x}{:02x}{:02x}", r, g, b),
-            Format::UppercaseHex => format!("#{:02X}{:02X}{:02X}", r, g, b),
+           Format::LowercaseHex(ref comp) => {
+               if *comp == HexCompaction::Compact && is_compactable((r, g, b)) {
+                   format!("#{:x}{:x}{:x}", r & 0xf, g & 0xf, b & 0xf)
+               } else {
+                   format!("#{:02x}{:02x}{:02x}", r, g, b)
+               }
+            },
+           Format::UppercaseHex(ref comp) => {
+               if *comp == HexCompaction::Compact && is_compactable((r, g, b)) {
+                   format!("#{:X}{:X}{:X}", r & 0xf, g & 0xf, b & 0xf)
+               } else {
+                   format!("#{:02X}{:02X}{:02X}", r, g, b)
+               }
+            },
             Format::Plain => format!("{};{};{}", r, g, b),
             Format::RGB => format!("rgb({}, {}, {})", r, g, b),
         }
@@ -214,6 +242,15 @@ fn test_format_color() {
     }
 }
 
+#[test]
+fn test_compaction() {
+    assert!(is_compactable((0xff, 0xff, 0xff)));
+    assert!(is_compactable((0xee, 0xee, 0xee)));
+    assert!(is_compactable((0x00, 0x00, 0x00)));
+    assert!(!is_compactable((0xf7, 0xf7, 0xf7)));
+    assert!(!is_compactable((0xff, 0xf7, 0xff)));
+}
+
 #[test]
 fn test_examples_from_readme() {
     let fmt: FormatString = "#%{02hr}%{02hg}%{02hb}".parse().unwrap();