bendns' repos / fimg
fast image operations
Diffstat (limited to 'src/overlay.rs')
-rw-r--r--src/overlay.rs55
1 files changed, 40 insertions, 15 deletions
diff --git a/src/overlay.rs b/src/overlay.rs
index 1a059e1..9624cb9 100644
--- a/src/overlay.rs
+++ b/src/overlay.rs
@@ -26,11 +26,17 @@ pub trait Overlay<W> {
/// SIMD accelerated rgba => rgb overlay.
///
/// See [blit](https://en.wikipedia.org/wiki/Bit_blit)
+///
+/// # Safety
+/// UB if rgb.len() % 3 != 0
+/// UB if rgba.len() % 4 != 0
unsafe fn blit(rgb: &mut [u8], rgba: &[u8]) {
let mut srci = 0;
let mut dsti = 0;
while dsti + 16 <= rgb.len() {
+ // SAFETY: i think it ok
let old: Simd<u8, 16> = Simd::from_slice(unsafe { rgb.get_unchecked(dsti..dsti + 16) });
+ // SAFETY: definetly ok
let new: Simd<u8, 16> = Simd::from_slice(unsafe { rgba.get_unchecked(srci..srci + 16) });
let threshold = new.simd_ge(Simd::splat(128)).to_int().cast::<u8>();
@@ -44,6 +50,7 @@ unsafe fn blit(rgb: &mut [u8], rgba: &[u8]) {
let new_rgb = simd_swizzle!(new, [0, 1, 2, 4, 5, 6, 8, 9, 10, 12, 13, 14, 0, 0, 0, 0]);
let blended = (new_rgb & mask) | (old & !mask);
+ // SAFETY: 4 * 4 == 16, so in bounds
blended.copy_to_slice(unsafe { rgb.get_unchecked_mut(dsti..dsti + 16) });
srci += 16;
@@ -51,10 +58,13 @@ unsafe fn blit(rgb: &mut [u8], rgba: &[u8]) {
}
while dsti + 3 <= rgb.len() {
+ // SAFETY: caller gurantees slice is big enough
if unsafe { *rgba.get_unchecked(srci + 3) } >= 128 {
- let src = unsafe { rgba.get_unchecked(srci..srci + 3) };
- let end = unsafe { rgb.get_unchecked_mut(dsti..dsti + 3) };
- unsafe { std::ptr::copy_nonoverlapping(src.as_ptr(), end.as_mut_ptr(), 3) };
+ // SAFETY: slice is big enough!
+ let src = unsafe { rgba.get_unchecked(srci..=srci + 2) };
+ // SAFETY: i hear it bound
+ let end = unsafe { rgb.get_unchecked_mut(dsti..=dsti + 2) };
+ end.copy_from_slice(src);
}
srci += 4;
@@ -69,16 +79,9 @@ impl Overlay<Image<&[u8], 4>> for Image<&mut [u8], 4> {
debug_assert!(self.height() == with.height());
for (i, other_pixels) in with.chunked().enumerate() {
if other_pixels[3] >= 128 {
- let idx_begin = unsafe { i.unchecked_mul(4) };
- let idx_end = unsafe { idx_begin.unchecked_add(4) };
- let own_pixels = unsafe { self.buffer.get_unchecked_mut(idx_begin..idx_end) };
- unsafe {
- std::ptr::copy_nonoverlapping(
- other_pixels.as_ptr(),
- own_pixels.as_mut_ptr(),
- 4,
- );
- };
+ // SAFETY: outside are bounds of index from slice
+ let own_pixels = unsafe { self.buffer.get_unchecked_mut(i * 4..i * 4 + 4) };
+ own_pixels.copy_from_slice(other_pixels);
}
}
self
@@ -88,9 +91,9 @@ impl Overlay<Image<&[u8], 4>> for Image<&mut [u8], 4> {
impl OverlayAt<Image<&[u8], 4>> for Image<&mut [u8], 3> {
#[inline]
unsafe fn overlay_at(&mut self, with: &Image<&[u8], 4>, x: u32, y: u32) -> &mut Self {
- // SAFETY: caller upholds these
+ // SAFETY: caller upholds this
unsafe { assert_unchecked!(x + with.width() <= self.width()) };
- unsafe { assert_unchecked!(y + with.height() <= self.height()) };
+ debug_assert!(y + with.height() <= self.height());
for j in 0..with.height() {
let i_x = j as usize * with.width() as usize * 4
..(j as usize + 1) * with.width() as usize * 4;
@@ -99,8 +102,11 @@ impl OverlayAt<Image<&[u8], 4>> for Image<&mut [u8], 3> {
+ x as usize
+ with.width() as usize)
* 3;
+ // SAFETY: index is in bounds
let rgb = unsafe { self.buffer.get_unchecked_mut(o_x) };
+ // SAFETY: bounds are outside index
let rgba = unsafe { with.buffer.get_unchecked(i_x) };
+ // SAFETY: arguments are 🟢
unsafe { blit(rgb, rgba) }
}
self
@@ -125,7 +131,9 @@ impl OverlayAt<Image<&[u8], 3>> for Image<&mut [u8], 3> {
let o_x = ((j + y as usize) * self.width() as usize + x as usize) * 3
..((j + y as usize) * self.width() as usize + x as usize + ($n as usize))
* 3;
+ // SAFETY: bounds are ✅
let a = unsafe { self.buffer.get_unchecked_mut(o_x) };
+ // SAFETY: we are in ⬜!
let b = unsafe { with.buffer.get_unchecked(i_x) };
a.copy_from_slice(b);
}
@@ -151,11 +159,13 @@ impl Overlay<Image<&[u8], 4>> for Image<&mut [u8], 3> {
.chunks_exact(with.width() as usize * 4)
.enumerate()
{
+ // SAFETY: all the bounds are good
let rgb = unsafe {
self.buffer.get_unchecked_mut(
i * with.width() as usize * 3..(i + 1) * with.width() as usize * 3,
)
};
+ // SAFETY: we have the rgb and rgba arguments right
unsafe { blit(rgb, chunk) };
}
self
@@ -164,15 +174,30 @@ impl Overlay<Image<&[u8], 4>> for Image<&mut [u8], 3> {
impl OverlayAt<Image<&[u8], 4>> for Image<&mut [u8], 4> {
#[inline]
+ /// Overlay with => self at coordinates x, y, without blending
+ ///
+ /// # Safety
+ /// UB if x, y is out of bounds
+ /// UB if x + with.width() > u32::MAX
+ /// UB if y + with.height() > u32::MAX
unsafe fn overlay_at(&mut self, with: &Image<&[u8], 4>, x: u32, y: u32) -> &mut Self {
for j in 0..with.height() {
for i in 0..with.width() {
+ // SAFETY: i, j is in bounds.
let index = unsafe { really_unsafe_index(i, j, with.width()) };
+ // SAFETY: using .pixel() results in horrible asm (+5k ns/iter)
let their_px = unsafe { with.buffer.get_unchecked(index * 4..index * 4 + 4) };
+ // SAFETY: must be sized right
if unsafe { *their_px.get_unchecked(3) } >= 128 {
+ // SAFETY:
+ // they said it cant go over.
+ // i dont know why, but this has performance importanceâ„¢
let x = unsafe { i.unchecked_add(x) };
+ // SAFETY: caller gurantees this cannot overflow.
let y = unsafe { j.unchecked_add(y) };
+ // SAFETY: compute the offset index.
let index = unsafe { really_unsafe_index(x, y, self.width()) };
+ // SAFETY: if everything else goes well, this is fine
let our_px = unsafe { self.buffer.get_unchecked_mut(index * 4..index * 4 + 4) };
our_px.copy_from_slice(their_px);
}