diff --git a/src/affine.rs b/src/affine.rs
index b0152a5..9fc7b3c 100644
--- a/src/affine.rs
+++ b/src/affine.rs
@@ -10,16 +10,17 @@ impl<const CHANNELS: usize> ImageCloner<'_, CHANNELS> {
     /// ```
     #[must_use = "function does not modify the original image"]
     pub fn flip_v(&self) -> Image<Vec<u8>, CHANNELS> {
-        let mut out = self.alloc();
+        let mut out = self.uninit();
         for y in 0..self.height() {
             for x in 0..self.width() {
                 // SAFETY: looping over self, all ok (could be safe versions, bounds would be elided)
                 let p = unsafe { self.pixel(x, y) };
                 // SAFETY: looping over self.
-                unsafe { out.set_pixel(x, self.height() - y - 1, p) };
+                unsafe { out.write(&p, (x, self.height() - y - 1)) };
             }
         }
-        out
+        // SAFETY: init
+        unsafe { out.assume_init() }
     }
 
     /// Flip an image horizontally
@@ -30,16 +31,17 @@ impl<const CHANNELS: usize> ImageCloner<'_, CHANNELS> {
     /// ```
     #[must_use = "function does not modify the original image"]
     pub fn flip_h(&self) -> Image<Vec<u8>, CHANNELS> {
-        let mut out = self.alloc();
+        let mut out = self.uninit();
         for y in 0..self.height() {
             for x in 0..self.width() {
                 // SAFETY: looping over self, all ok
                 let p = unsafe { self.pixel(x, y) };
                 // SAFETY: looping over self, all ok
-                unsafe { out.set_pixel(self.width() - x - 1, y, p) };
+                unsafe { out.write(&p, (self.width() - x - 1, y)) };
             }
         }
-        out
+        // SAFETY: init
+        unsafe { out.assume_init() }
     }
 }
 
diff --git a/src/cloner.rs b/src/cloner.rs
index b38aedd..f110c1c 100644
--- a/src/cloner.rs
+++ b/src/cloner.rs
@@ -5,7 +5,7 @@
 //! # let i = Image::<_, 1>::alloc(5, 5);
 //! unsafe { i.cloner().rot_270() };
 //! ```
-use crate::Image;
+use crate::{uninit, Image};
 
 /// A neat way to clone a image.
 ///
@@ -19,6 +19,11 @@ impl<'a, const C: usize> ImageCloner<'a, C> {
         self.0.to_owned()
     }
 
+    /// create a new uninit image the right size for use
+    pub(crate) fn uninit(&self) -> uninit::Image<u8, C> {
+        uninit::Image::new(self.width, self.height)
+    }
+
     /// Create a [`ImageCloner`] from a <code>[Image]<&\[[u8]\]></code>
     pub const fn from(i: Image<&'a [u8], C>) -> Self {
         Self(i)
diff --git a/src/lib.rs b/src/lib.rs
index 6e7131f..098fc03 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -49,6 +49,7 @@
 //! - `default`: \[`save`, `scale`\].
 #![feature(
     maybe_uninit_write_slice,
+    hint_assert_unchecked,
     slice_swap_unchecked,
     generic_const_exprs,
     slice_as_chunks,
@@ -72,7 +73,7 @@
     missing_docs
 )]
 #![allow(clippy::zero_prefixed_literal, incomplete_features)]
-use std::{num::NonZeroU32, ops::Range};
+use std::{hint::assert_unchecked, num::NonZeroU32, ops::Range};
 
 mod affine;
 #[cfg(feature = "blur")]
@@ -122,25 +123,6 @@ impl<T> CopyWithinUnchecked for [T] {
     }
 }
 
-/// like assert!(), but causes undefined behaviour at runtime when the condition is not met.
-///
-/// # Safety
-///
-/// UB if condition is false.
-macro_rules! assert_unchecked {
-    ($cond:expr) => {{
-        if !$cond {
-            #[cfg(debug_assertions)]
-            let _ = ::core::ptr::NonNull::<()>::dangling().as_ref(); // force unsafe wrapping block
-            #[cfg(debug_assertions)]
-            panic!("assertion failed: {} returned false", stringify!($cond));
-            #[cfg(not(debug_assertions))]
-            std::hint::unreachable_unchecked()
-        }
-    }};
-}
-use assert_unchecked;
-
 trait At {
     fn at<const C: usize>(self, x: u32, y: u32) -> usize;
 }
@@ -455,9 +437,9 @@ impl<T, const CHANNELS: usize> Image<T, CHANNELS> {
         T: AsRef<[U]>,
     {
         // SAFETY: 0 sized images illegal
-        unsafe { assert_unchecked!(self.len() > CHANNELS) };
+        unsafe { assert_unchecked(self.len() > CHANNELS) };
         // SAFETY: no half pixels!
-        unsafe { assert_unchecked!(self.len() % CHANNELS == 0) };
+        unsafe { assert_unchecked(self.len() % CHANNELS == 0) };
         self.buffer().as_ref().array_chunks::<CHANNELS>()
     }
 
@@ -546,9 +528,9 @@ impl<T: AsMut<[u8]> + AsRef<[u8]>, const CHANNELS: usize> Image<T, CHANNELS> {
     /// Returns a iterator over every pixel, mutably
     pub fn chunked_mut(&mut self) -> impl Iterator<Item = &mut [u8; CHANNELS]> {
         // SAFETY: 0 sized images are not allowed
-        unsafe { assert_unchecked!(self.len() > CHANNELS) };
+        unsafe { assert_unchecked(self.len() > CHANNELS) };
         // SAFETY: buffer cannot have half pixels
-        unsafe { assert_unchecked!(self.len() % CHANNELS == 0) };
+        unsafe { assert_unchecked(self.len() % CHANNELS == 0) };
         self.buffer.as_mut().array_chunks_mut::<CHANNELS>()
     }
 
diff --git a/src/overlay.rs b/src/overlay.rs
index dbb7a0a..eef4272 100644
--- a/src/overlay.rs
+++ b/src/overlay.rs
@@ -160,7 +160,7 @@ impl<T: AsMut<[u8]> + AsRef<[u8]>, U: AsRef<[u8]>> OverlayAt<Image<U, 4>> for Im
     #[inline]
     unsafe fn overlay_at(&mut self, with: &Image<U, 4>, x: u32, y: u32) -> &mut Self {
         // SAFETY: caller upholds this
-        unsafe { assert_unchecked!(x + with.width() <= self.width()) };
+        unsafe { assert_unchecked(x + with.width() <= self.width()) };
         debug_assert!(y + with.height() <= self.height());
         for j in 0..with.height() {
             let i_x = j as usize * with.width() as usize * 4
diff --git a/src/span.rs b/src/span.rs
index 7ac76c9..69a01ad 100644
--- a/src/span.rs
+++ b/src/span.rs
@@ -32,3 +32,11 @@ impl Span for Range<(u32, u32)> {
         i.at::<C>(sx, sy)..i.at::<C>(ex, ey)
     }
 }
+
+impl Sealed for (u32, u32) {}
+impl Span for (u32, u32) {
+    #[inline(always)]
+    fn range<const C: usize>(self, i: (u32, u32)) -> Range<usize> {
+        i.at::<C>(self.0, self.1)..i.at::<C>(self.0, self.1) + C
+    }
+}
diff --git a/src/uninit.rs b/src/uninit.rs
index 3555beb..c4c341b 100644
--- a/src/uninit.rs
+++ b/src/uninit.rs
@@ -1,9 +1,14 @@
 //! the houser of uninitialized memory. €$@!0В𴬔!℡
 //!
 //! contains [`Image`], an uninitialized image.
-use std::{mem::MaybeUninit, num::NonZeroU32};
+use std::{
+    hint::assert_unchecked,
+    mem::MaybeUninit,
+    num::NonZeroU32,
+    ops::{Index, IndexMut},
+};
 
-use crate::CopyWithinUnchecked;
+use crate::{span::Span, CopyWithinUnchecked};
 
 /// A uninitialized image. Be sure to initialize it!
 pub struct Image<T: Copy, const CHANNELS: usize> {
@@ -13,6 +18,14 @@ pub struct Image<T: Copy, const CHANNELS: usize> {
     height: NonZeroU32,
 }
 
+impl<I: Span, T: Copy, const C: usize> Index<I> for Image<T, C> {
+    type Output = [T];
+
+    fn index(&self, index: I) -> &Self::Output {
+        &self.buffer()[index.range::<C>((self.width(), self.height()))]
+    }
+}
+
 impl<T: Copy, const CHANNELS: usize> Image<T, CHANNELS> {
     /// Create a new uninit image. This is not init.
     pub fn new(width: NonZeroU32, height: NonZeroU32) -> Self {
@@ -27,19 +40,31 @@ impl<T: Copy, const CHANNELS: usize> Image<T, CHANNELS> {
     ///
     /// # Safety
     /// index must be in bounds.
-    pub unsafe fn write(&mut self, data: &[T], i: impl crate::span::Span) {
-        let range = i.range::<CHANNELS>((self.width(), self.height()));
-        // SAFETY: write
-        let dat = unsafe { self.buf().get_unchecked_mut(range) };
+    /// data and indexed range must have same len.
+    pub unsafe fn write(&mut self, data: &[T], i: impl Span) {
+        // SAFETY: caller
+        let dat = unsafe { self.slice(i) };
+        // SAFETY: caller
+        unsafe { assert_unchecked(dat.len() == data.len()) };
         MaybeUninit::write_slice(dat, data);
     }
 
+    /// Slice the image.
+    ///
+    /// # Safety
+    /// index must be in bounds.
+    pub unsafe fn slice(&mut self, i: impl Span) -> &mut [MaybeUninit<T>] {
+        let range = i.range::<CHANNELS>((self.width(), self.height()));
+        // SAFETY: assured
+        unsafe { self.buf().get_unchecked_mut(range) }
+    }
+
     /// Copy a range to a position.
     ///
     /// # Safety
     ///
     /// both parts must be in bounds.
-    pub unsafe fn copy_within(&mut self, i: impl crate::span::Span, to: usize) {
+    pub unsafe fn copy_within(&mut self, i: impl Span, to: usize) {
         let range = i.range::<CHANNELS>((self.width(), self.height()));
         // SAFETY: copy!
         unsafe { self.buf().copy_within_unchecked(range, to) };