feat: rgb_cmyk_conversion

Author: ali77gh

DIRECTORY.md

@@ -55,6 +55,7 @@
     * [Hexadecimal To Decimal](https://github.com/TheAlgorithms/Rust/blob/master/src/conversions/hexadecimal_to_decimal.rs)
     * [Octal To Binary](https://github.com/TheAlgorithms/Rust/blob/master/src/conversions/octal_to_binary.rs)
     * [Octal To Decimal](https://github.com/TheAlgorithms/Rust/blob/master/src/conversions/octal_to_decimal.rs)
+    * [RGB to CMYK](https://github.com/TheAlgorithms/Rust/blob/master/src/conversions/rgb_cmyk_conversion.rs)
   * Data Structures
     * [Avl Tree](https://github.com/TheAlgorithms/Rust/blob/master/src/data_structures/avl_tree.rs)
     * [B Tree](https://github.com/TheAlgorithms/Rust/blob/master/src/data_structures/b_tree.rs)

src/conversions/mod.rs

@@ -6,6 +6,7 @@ mod hexadecimal_to_binary;
 mod hexadecimal_to_decimal;
 mod octal_to_binary;
 mod octal_to_decimal;
+mod rgb_cmyk_conversion;
 pub use self::binary_to_decimal::binary_to_decimal;
 pub use self::binary_to_hexadecimal::binary_to_hexadecimal;
 pub use self::decimal_to_binary::decimal_to_binary;
@@ -14,3 +15,4 @@ pub use self::hexadecimal_to_binary::hexadecimal_to_binary;
 pub use self::hexadecimal_to_decimal::hexadecimal_to_decimal;
 pub use self::octal_to_binary::octal_to_binary;
 pub use self::octal_to_decimal::octal_to_decimal;
+pub use self::rgb_cmyk_conversion::rgb_to_cmyk;

src/conversions/rgb_cmyk_conversion.rs

@@ -0,0 +1,56 @@
+/// Author : https://github.com/ali77gh\
+/// References:\
+/// RGB:  https://en.wikipedia.org/wiki/RGB_color_model\
+/// CMYK: https://en.wikipedia.org/wiki/CMYK_color_model\
+
+/// This function Converts RGB to CMYK format
+///
+/// ### Params
+/// * `r` - red
+/// * `g` - green
+/// * `b` - blue
+///
+/// ### Returns
+/// (C, M, Y, K)
+pub fn rgb_to_cmyk(r: u8, g: u8, b: u8) -> (u8, u8, u8, u8) {
+    // Safety: no need to check if input is positive and less than 255 because it's u8
+
+    // change scale from [0,255] to [0,1]
+    let (r, g, b) = (r as f64 / 255f64, g as f64 / 255f64, b as f64 / 255f64);
+
+    match 1f64 - r.max(g).max(b) {
+        1f64 => (0, 0, 0, 100), // pure black
+        k => (
+            (100f64 * (1f64 - r - k) / (1f64 - k)) as u8, // c
+            (100f64 * (1f64 - g - k) / (1f64 - k)) as u8, // m
+            (100f64 * (1f64 - b - k) / (1f64 - k)) as u8, // y
+            (100f64 * k) as u8,                           // k
+        ),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn rgb_to_cmyk_test() {
+        // white
+        assert_eq!(rgb_to_cmyk(255, 255, 255), (0, 0, 0, 0));
+
+        // gray
+        assert_eq!(rgb_to_cmyk(128, 128, 128), (0, 0, 0, 49));
+
+        // black
+        assert_eq!(rgb_to_cmyk(0, 0, 0), (0, 0, 0, 100));
+
+        // red
+        assert_eq!(rgb_to_cmyk(255, 0, 0), (0, 100, 100, 0));
+
+        // green
+        assert_eq!(rgb_to_cmyk(0, 255, 0), (100, 0, 100, 0));
+
+        // blue
+        assert_eq!(rgb_to_cmyk(0, 0, 255), (100, 100, 0, 0));
+    }
+}