feat: rgb_cmyk_conversion (#831)

* feat: rgb_cmyk_conversion

* Update src/conversions/rgb_cmyk_conversion.rs

Co-authored-by: Piotr Idzik <[email protected]>

* Update src/conversions/rgb_cmyk_conversion.rs

Co-authored-by: Piotr Idzik <[email protected]>

* fix: compile error (switching macro and distruction to tuple)

* style: use `rgb` in tests

---------

Co-authored-by: Piotr Idzik <[email protected]>

DIRECTORY.md

@@ -56,6 +56,7 @@
     * [Length Conversion](https://github.com/TheAlgorithms/Rust/blob/master/src/conversions/length_conversion.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

@@ -7,6 +7,7 @@ mod hexadecimal_to_decimal;
 mod length_conversion;
 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;
@@ -16,3 +17,4 @@ pub use self::hexadecimal_to_decimal::hexadecimal_to_decimal;
 pub use self::length_conversion::length_conversion;
 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 +1,60 @@
+/// 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(rgb: (u8, u8, 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) = (
+        rgb.0 as f64 / 255f64,
+        rgb.1 as f64 / 255f64,
+        rgb.2 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::*;
+
+    macro_rules! test_rgb_to_cmyk {
+        ($($name:ident: $tc:expr,)*) => {
+            $(
+                #[test]
+                fn $name() {
+                    let (rgb, cmyk) = $tc;
+                    assert_eq!(rgb_to_cmyk(rgb), cmyk);
+                }
+            )*
+        }
+    }
+
+    test_rgb_to_cmyk! {
+        white: ((255, 255, 255), (0, 0, 0, 0)),
+        gray: ((128, 128, 128), (0, 0, 0, 49)),
+        black: ((0, 0, 0), (0, 0, 0, 100)),
+        red: ((255, 0, 0), (0, 100, 100, 0)),
+        green: ((0, 255, 0), (100, 0, 100, 0)),
+        blue: ((0, 0, 255), (100, 100, 0, 0)),
+    }
+}