fix: pack rgb seems to be wrong (#10)

* transmute for bitwise reinterpretation

* safe bit casting

src/pcl_utils.rs

@@ -2,14 +2,16 @@ use crate::{ConversionError, MetaNames, PointConvertible, PointMeta};
 
 #[inline]
 fn pack_rgb(r: u8, g: u8, b: u8) -> f32 {
-    ((r as u32) << 16) as f32 + ((g as u32) << 8) as f32 + (b as u32) as f32
+    let packed = ((r as u32) << 16) + ((g as u32) << 8) + (b as u32);
+    f32::from_bits(packed)
 }
 
 #[inline]
 fn unpack_rgb(rgb: f32) -> [u8; 3] {
-    let r: u8 = ((rgb as u32) >> 16) as u8;
+    let packed: u32 = rgb.to_bits();
-    let g: u8 = ((rgb as u32) >> 8) as u8;
+    let r: u8 = (packed >> 16) as u8;
-    let b: u8 = (rgb as u32) as u8;
+    let g: u8 = (packed >> 8) as u8;
+    let b: u8 = packed as u8;
     [r, g, b]
 }