added floating point precision test

tests/floats.rs

@@ -0,0 +1,57 @@
+use std::ops::Shr;
+
+#[test]
+pub fn test_conversion_u16() {
+    let actual = (u64::MIN..=u16::MAX as u64).into_iter().sum::<u64>()/(u16::MAX as u64+1);
+
+    let mut average = 0.0;
+    let fac = 1.0/u16::MAX as f32;
+    for f in u16::MIN..=u16::MAX {
+        average += f as f32 * fac;
+    }
+
+    assert_eq!(actual, average as u64);
+}
+
+fn hash(x: u8) -> u8 {
+    let mut k = (x as f32 * 349857.3456).sin();
+    k = k - k.floor();
+    (k * 255.) as u8
+}
+
+#[test]
+pub fn test_arithmetic() {
+
+    let lum_f32 = |r: f32, g: f32, b: f32| {
+        0.2126 * r + 0.7152 * g + 0.0722 * b
+    };
+
+    let lum_u8 = |r: u8, g: u8, b: u8| {
+        (r as u64 * 913110047u64).shr(32) + (g as u64 * 3071760610u64).shr(32) + (b as u64 * 310096639u64).shr(32)
+    };
+
+    let mut colors = Vec::new();
+
+    for a in 1..4096i32 {
+        colors.push((hash(a as u8), hash(a.wrapping_sub(98) as u8), hash(a.wrapping_add(178) as u8)));
+    }
+
+    let lum0 = colors.iter().map(|(a,b,c)| lum_f32(*a as f32, *b as f32, *c as f32)).sum::<f32>() / colors.len() as f32;
+    let lum1 = colors.iter().map(|(a,b,c)| lum_u8(*a,*b,*c) as u64).sum::<u64>() / colors.len() as u64;
+
+    let mut lum2 = 0.;
+    let w = 1./colors.len() as f32;
+    for (r,g,b) in colors.iter() {
+        let a = lum_f32(*r as f32, *g as f32, *b as f32);
+        lum2 += a * w;
+    }
+
+    println!("{lum0}");
+    println!("{lum2}");
+    println!("{lum1}");
+
+    let lf = (lum_f32(1., 0.5, 0.333) * 255.0) as u8;
+    println!("{lf}");
+    let lu = lum_u8(255, 127, 85);
+    println!("{lu}");
+}