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Improved nearest interpolation #13

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Merged
awxkee merged 1 commit into from
Feb 10, 2026
Merged

Improved nearest interpolation #13

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26 changes: 14 additions & 12 deletions src/resize_nearest.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -39,11 +39,12 @@ pub(crate) fn resize_nearest<T: Copy + Send + Sync, const CHANNELS: usize>(
dst_width: usize,
dst_height: usize,
) {
let x_scale = src_width as f32 / dst_width as f32;
let y_scale = src_height as f32 / dst_height as f32;
const SHIFT: i32 = 32;

let clip_width = src_width as f32 - 1f32;
let clip_height = src_height as f32 - 1f32;
let k_x: u64 = ((src_width as u64) << SHIFT) / dst_width as u64;
let k_y: u64 = ((src_height as u64) << SHIFT) / dst_height as u64;
let k_x_half: u64 = k_x >> 1;
let k_y_half: u64 = k_y >> 1;

let dst_stride = dst_width * CHANNELS;
let src_stride = src_width * CHANNELS;
Expand All @@ -59,14 +60,13 @@ pub(crate) fn resize_nearest<T: Copy + Send + Sync, const CHANNELS: usize>(
}

iter.enumerate().for_each(|(y, dst_row)| {
for (x, dst_chunk) in dst_row.chunks_exact_mut(CHANNELS).enumerate() {
let src_x = ((x as f32 + 0.5f32) * x_scale - 0.5f32)
.min(clip_width)
.max(0f32) as usize;
let src_y = ((y as f32 + 0.5f32) * y_scale - 0.5f32)
.min(clip_height)
.max(0f32) as usize;
let src_offset_y = src_y * src_stride;
let src_y = ((y as u64 * k_y + k_y_half) >> SHIFT) as usize;
let src_offset_y = src_y * src_stride;

let mut src_x_fixed = k_x_half;
for dst_chunk in dst_row.chunks_exact_mut(CHANNELS) {
let src_x = (src_x_fixed >> SHIFT) as usize;

let src_px = src_x * CHANNELS;
let offset = src_offset_y + src_px;

Expand All @@ -75,6 +75,8 @@ pub(crate) fn resize_nearest<T: Copy + Send + Sync, const CHANNELS: usize>(
for (src, dst) in src_slice.iter().zip(dst_chunk.iter_mut()) {
*dst = *src;
}

src_x_fixed += k_x;
}
});
}