Use simpler bytemuck impl if as-bytes is off

src/as_bytes.rs

@@ -13,6 +13,7 @@ unsafe impl<T> crate::Zeroable for RGB<T> where T: crate::Zeroable {}
 unsafe impl<T> crate::Zeroable for BGR<T> where T: crate::Zeroable {}
 
 #[cfg(feature = "as-bytes")]
+/// This is unsound. You can disable `as-bytes` feature, enable `bytemuck`, and use `bytemuck::cast_slice()` instead.
 unsafe impl<T, A> crate::Zeroable for ABGR<T, A> where T: crate::Zeroable, A: crate::Zeroable {
     #[track_caller]
     #[inline(always)]
@@ -32,12 +33,15 @@ const fn assert_no_padding<T, A, S>() {
 }
 
 #[cfg(feature = "as-bytes")]
+/// This is unsound. You can disable `as-bytes` feature, enable `bytemuck`, and use `bytemuck::cast_slice()` instead.
 unsafe impl<T, A> crate::Pod for RGBA<T, A> where T: crate::Pod, A: crate::Pod {}
 
 #[cfg(feature = "as-bytes")]
+/// This is unsound. You can disable `as-bytes` feature, enable `bytemuck`, and use `bytemuck::cast_slice()` instead.
 unsafe impl<T, A> crate::Pod for BGRA<T, A> where T: crate::Pod, A: crate::Pod {}
 
 #[cfg(feature = "as-bytes")]
+/// This is unsound. You can disable `as-bytes` feature, enable `bytemuck`, and use `bytemuck::cast_slice()` instead.
 unsafe impl<T, A> crate::Zeroable for RGBA<T, A> where T: crate::Zeroable, A: crate::Zeroable {
     #[track_caller]
     #[inline(always)]
@@ -50,12 +54,15 @@ unsafe impl<T, A> crate::Zeroable for RGBA<T, A> where T: crate::Zeroable, A: cr
 }
 
 #[cfg(feature = "as-bytes")]
+/// This is unsound. You can disable `as-bytes` feature, enable `bytemuck`, and use `bytemuck::cast_slice()` instead.
 unsafe impl<T, A> crate::Pod for ARGB<T, A> where T: crate::Pod, A: crate::Pod {}
 
 #[cfg(feature = "as-bytes")]
+/// This is unsound. You can disable `as-bytes` feature, enable `bytemuck`, and use `bytemuck::cast_slice()` instead.
 unsafe impl<T, A> crate::Pod for ABGR<T, A> where T: crate::Pod, A: crate::Pod {}
 
 #[cfg(feature = "as-bytes")]
+/// This is unsound. You can disable `as-bytes` feature, enable `bytemuck`, and use `bytemuck::cast_slice()` instead.
 unsafe impl<T, A> crate::Zeroable for ARGB<T, A> where T: crate::Zeroable, A: crate::Zeroable {
     #[track_caller]
     #[inline(always)]
@@ -68,6 +75,7 @@ unsafe impl<T, A> crate::Zeroable for ARGB<T, A> where T: crate::Zeroable, A: cr
 }
 
 #[cfg(feature = "as-bytes")]
+/// This is unsound. You can disable `as-bytes` feature, enable `bytemuck`, and use `bytemuck::cast_slice()` instead.
 unsafe impl<T, A> crate::Zeroable for BGRA<T, A> where T: crate::Zeroable, A: crate::Zeroable {
     #[track_caller]
     #[inline(always)]
@@ -82,10 +90,12 @@ unsafe impl<T, A> crate::Zeroable for BGRA<T, A> where T: crate::Zeroable, A: cr
 #[cfg(feature = "as-bytes")]
 unsafe impl<T> crate::Pod for Gray<T> where T: crate::Pod {}
 #[cfg(feature = "as-bytes")]
+/// This is unsound. You can disable `as-bytes` feature, enable `bytemuck`, and use `bytemuck::cast_slice()` instead.
 unsafe impl<T, A> crate::Pod for GrayAlpha<T, A> where T: crate::Pod, A: crate::Pod {}
 #[cfg(feature = "as-bytes")]
 unsafe impl<T> crate::Zeroable for Gray<T> where T: crate::Zeroable {}
 #[cfg(feature = "as-bytes")]
+/// This is unsound. You can disable `as-bytes` feature, enable `bytemuck`, and use `bytemuck::cast_slice()` instead.
 unsafe impl<T, A> crate::Zeroable for GrayAlpha<T, A> where T: crate::Zeroable, A: crate::Zeroable {
     #[track_caller]
     #[inline(always)]

src/bytemuck_impl.rs

@@ -0,0 +1,23 @@
+use crate::{Abgr, Argb, Bgr, Bgra, Grb, Rgb, Rgba};
+use crate::formats::gray_a::GrayA;
+use crate::formats::gray_alpha::GrayAlpha_v08;
+use crate::formats::gray::Gray_v08;
+
+macro_rules! bytemuck {
+    ($name:ident) => {
+        unsafe impl<T: ::bytemuck::Zeroable> ::bytemuck::Zeroable for $name<T> {}
+        unsafe impl<T: ::bytemuck::Pod> ::bytemuck::Pod for $name<T> {}
+    };
+}
+
+bytemuck!(Rgb);
+bytemuck!(Bgr);
+bytemuck!(Grb);
+bytemuck!(Rgba);
+bytemuck!(Argb);
+bytemuck!(Bgra);
+bytemuck!(Abgr);
+bytemuck!(GrayA);
+
+bytemuck!(GrayAlpha_v08);
+bytemuck!(Gray_v08);

src/lib.rs

@@ -83,6 +83,8 @@ pub(crate) mod legacy {
 
 pub use legacy::alt;
 
+#[cfg(all(feature = "bytemuck", not(feature = "as-bytes")))]
+mod bytemuck_impl;
 #[cfg(feature = "as-bytes")]
 mod as_bytes;