bendns' repos / fimg
fast image operations
Diffstat (limited to 'src/scale/traits.rs')
-rw-r--r--src/scale/traits.rs91
1 files changed, 91 insertions, 0 deletions
diff --git a/src/scale/traits.rs b/src/scale/traits.rs
new file mode 100644
index 0000000..66d1ddb
--- /dev/null
+++ b/src/scale/traits.rs
@@ -0,0 +1,91 @@
+//! implementation detail for scaling. look into if you want to add a algorithm
+use std::num::NonZeroU32;
+
+#[doc(hidden)]
+mod seal {
+ #[doc(hidden)]
+ pub trait Sealed {}
+}
+
+use seal::Sealed;
+
+use crate::Image;
+impl Sealed for ChannelCount<1> {}
+impl Sealed for ChannelCount<2> {}
+impl Sealed for ChannelCount<3> {}
+impl Sealed for ChannelCount<4> {}
+
+/// How to scale a image
+pub trait ScalingAlgorithm {
+ /// Y/Rgb scale
+ fn scale_opaque<const N: usize>(
+ i: Image<&[u8], N>,
+ w: NonZeroU32,
+ h: NonZeroU32,
+ ) -> Image<Box<[u8]>, N>
+ where
+ ChannelCount<N>: ToImageView<N>;
+ /// Ya/Rgba scale
+ fn scale_transparent<const N: usize>(
+ i: Image<&mut [u8], N>,
+ w: NonZeroU32,
+ h: NonZeroU32,
+ ) -> Image<Box<[u8]>, N>
+ where
+ ChannelCount<N>: AlphaDiv<N>;
+}
+
+/// helper
+pub trait ToImageView<const N: usize>: Sealed {
+ #[doc(hidden)]
+ type P: fr::PixelExt + fr::Convolution;
+ #[doc(hidden)]
+ fn wrap(i: Image<&[u8], N>) -> fr::ImageView<Self::P>;
+}
+
+/// helper
+pub trait AlphaDiv<const N: usize>: Sealed + ToImageView<N> {
+ #[doc(hidden)]
+ type P: fr::PixelExt + fr::Convolution + fr::AlphaMulDiv;
+ #[doc(hidden)]
+ fn handle(i: Image<&mut [u8], N>) -> fr::Image<'_, <Self as AlphaDiv<N>>::P>;
+}
+
+/// Generic helper for [`Image`] and [`fr::Image`] transfers.
+pub struct ChannelCount<const N: usize> {}
+
+macro_rules! tiv {
+ ($n:literal, $which:ident) => {
+ impl ToImageView<$n> for ChannelCount<$n> {
+ type P = fr::$which;
+ fn wrap(i: Image<&[u8], $n>) -> fr::ImageView<Self::P> {
+ // SAFETY: same conds
+ unsafe { fr::ImageView::new(i.width, i.height, i.buffer()) }
+ }
+ }
+ };
+}
+
+tiv!(1, U8);
+tiv!(2, U8x2);
+tiv!(3, U8x3);
+tiv!(4, U8x4);
+
+macro_rules! adiv {
+ ($n:literal, $which:ident) => {
+ impl AlphaDiv<$n> for ChannelCount<$n> {
+ type P = fr::$which;
+ fn handle(i: Image<&mut [u8], $n>) -> fr::Image<<Self as AlphaDiv<$n>>::P> {
+ // SAFETY: we kinda have the same conditions
+ let mut i = unsafe { fr::Image::from_slice_u8(i.width, i.height, i.take_buffer()) };
+ // SAFETY: mhm
+ unsafe { fr::MulDiv::default().multiply_alpha_inplace(&mut i.view_mut()) };
+
+ i
+ }
+ }
+ };
+}
+
+adiv!(2, U8x2);
+adiv!(4, U8x4);