WIP no-std-check OK

- `cargo +nightly-2022-10-22 no-std-check --no-default-features --features=alloc` OK
- `cargo test --no-default-features --features=alloc` OK

Author: n-prat

src/color.rs

@@ -4,6 +4,9 @@ use num_traits::{NumCast, ToPrimitive, Zero};
 
 use crate::traits::{Enlargeable, Pixel, Primitive};
 
+#[cfg(not(feature = "std"))]
+use num_traits::float::FloatCore;
+
 /// An enumeration over supported color types and bit depths
 #[derive(Copy, PartialEq, Eq, Debug, Clone, Hash)]
 #[non_exhaustive]

src/imageops/colorops.rs

@@ -3,6 +3,9 @@ use alloc::vec::Vec;
 use core::f64::consts::PI;
 use num_traits::NumCast;
 
+#[cfg(not(feature = "std"))]
+use num_traits::Float;
+
 use crate::color::{FromColor, IntoColor, Luma, LumaA, Rgba};
 use crate::image::{GenericImage, GenericImageView};
 use crate::traits::{Pixel, Primitive};

src/imageops/sample.rs

@@ -8,6 +8,9 @@ use core::f32;
 
 use num_traits::{NumCast, ToPrimitive, Zero};
 
+#[cfg(not(feature = "std"))]
+use num_traits::Float;
+
 use crate::image::{GenericImage, GenericImageView};
 use crate::traits::{Enlargeable, Pixel, Primitive};
 use crate::utils::clamp;

src/math/utils.rs

@@ -2,6 +2,9 @@
 
 use core::cmp::max;
 
+#[cfg(not(feature = "std"))]
+use num_traits::Float;
+
 /// Calculates the width and height an image should be resized to.
 /// This preserves aspect ratio, and based on the `fill` parameter
 /// will either fill the dimensions to fit inside the smaller constraint