From 16fbab6ca237232051ff7f42d8b319c0d103012c Mon Sep 17 00:00:00 2001
From: bendn <bend.n@outlook.com>
Date: Thu, 2 Nov 2023 09:15:05 +0700
Subject: [PATCH] generic

---
 src/overlay.rs         | 40 +++++++---------------------------------
 src/pixels/blending.rs | 10 +++++++++-
 2 files changed, 16 insertions(+), 34 deletions(-)

diff --git a/src/overlay.rs b/src/overlay.rs
index d364a76..8561ab5 100644
--- a/src/overlay.rs
+++ b/src/overlay.rs
@@ -129,20 +129,16 @@ impl<T: AsMut<[u8]> + AsRef<[u8]>, U: AsRef<[u8]>> Overlay<Image<U, 4>> for Imag
     }
 }
 
-impl BlendingOverlay<Image<&[u8], 4>> for Image<&mut [u8], 4> {
+impl<const A: usize, const B: usize, T: AsMut<[u8]> + AsRef<[u8]>, U: AsRef<[u8]>>
+    BlendingOverlay<Image<U, B>> for Image<T, A>
+where
+    [u8; A]: Blend<B>,
+{
     #[inline]
-    unsafe fn overlay_blended(&mut self, with: &Image<&[u8], 4>) -> &mut Self {
+    unsafe fn overlay_blended(&mut self, with: &Image<U, B>) -> &mut Self {
         debug_assert!(self.width() == with.width());
         debug_assert!(self.height() == with.height());
-        for (i, other_pixels) in with.chunked().enumerate() {
-            // SAFETY: caller assures us, all is well.
-            let own_pixels = unsafe {
-                &mut *(self
-                    .buffer
-                    .as_mut()
-                    .get_unchecked_mut(i * 4..i * 4 + 4)
-                    .as_mut_ptr() as *mut [u8; 4])
-            };
+        for (other_pixels, own_pixels) in with.chunked().zip(self.chunked_mut()) {
             own_pixels.blend(*other_pixels);
         }
         self
@@ -259,28 +255,6 @@ impl<T: AsMut<[u8]> + AsRef<[u8]>, U: AsRef<[u8]>> Overlay<Image<U, 4>> for Imag
     }
 }
 
-impl<T: AsMut<[u8]> + AsRef<[u8]>, U: AsRef<[u8]>> BlendingOverlay<Image<U, 4>> for Image<T, 3> {
-    #[inline]
-    unsafe fn overlay_blended(&mut self, with: &Image<U, 4>) -> &mut Self {
-        debug_assert!(self.width() == with.width());
-        debug_assert!(self.height() == with.height());
-        for (i, other_pixels) in with.chunked().enumerate() {
-            // SAFETY: caller assures us, all is well.
-            let [r, g, b] = unsafe {
-                &mut *(self
-                    .buffer
-                    .as_mut()
-                    .get_unchecked_mut(i * 3..i * 3 + 3)
-                    .as_mut_ptr() as *mut [u8; 3])
-            };
-            let mut us = [*r, *g, *b, 255];
-            us.blend(*other_pixels);
-            (*r, *g, *b) = (us[0], us[1], us[2]);
-        }
-        self
-    }
-}
-
 impl ClonerOverlay<4, 3> for ImageCloner<'_, 3> {
     #[inline]
     #[must_use = "function does not modify the original image"]
diff --git a/src/pixels/blending.rs b/src/pixels/blending.rs
index 17ce141..a65861e 100644
--- a/src/pixels/blending.rs
+++ b/src/pixels/blending.rs
@@ -1,5 +1,5 @@
 //! module for pixel blending ops
-use super::{unfloat, Floatify, PMap, Trunc, Unfloatify};
+use super::{convert::PFrom, unfloat, Floatify, PMap, Trunc, Unfloatify};
 use umath::FF32;
 
 /// Trait for blending pixels together.
@@ -41,6 +41,14 @@ impl Blend<3> for [u8; 3] {
     }
 }
 
+impl Blend<4> for [u8; 3] {
+    fn blend(&mut self, with: [u8; 4]) {
+        let mut us: [u8; 4] = PFrom::pfrom(*self);
+        us.blend(with);
+        *self = PFrom::pfrom(us);
+    }
+}
+
 impl Blend<2> for [u8; 2] {
     fn blend(&mut self, with: [u8; 2]) {
         let bg = self.float();