//! Handles image overlay
use super::{assert_unchecked, really_unsafe_index, Image};
use std::simd::SimdInt;
use std::simd::SimdPartialOrd;
use std::simd::{simd_swizzle, Simd};
/// Trait for layering a image ontop of another, with a offset to the second image.
pub trait OverlayAt<W> {
/// Overlay with => self at coordinates x, y, without blending
/// # Safety
///
/// UB if x, y is out of bounds
unsafe fn overlay_at(&mut self, with: &W, x: u32, y: u32) -> &mut Self;
}
/// Trait for layering images ontop of each other.
/// Think `magick a b -layers flatten a`
pub trait Overlay<W> {
/// Overlay with => self (does not blend)
/// # Safety
///
/// UB if a.width != b.width || a.height != b.height
unsafe fn overlay(&mut self, with: &W) -> &mut Self;
}
#[inline]
/// 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>();
let mut mask = simd_swizzle!(
threshold,
[3, 3, 3, 7, 7, 7, 11, 11, 11, 15, 15, 15, 0, 0, 0, 0]
);
mask &= Simd::from_array([
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 0, 0,
]);
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;
dsti += 12;
}
while dsti + 3 <= rgb.len() {
// SAFETY: caller gurantees slice is big enough
if unsafe { *rgba.get_unchecked(srci + 3) } >= 128 {
// 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;
dsti += 3;
}
}
impl Overlay<Image<&[u8], 4>> for Image<&mut [u8], 4> {
#[inline]
unsafe fn overlay(&mut self, with: &Image<&[u8], 4>) -> &mut Self {
debug_assert!(self.width() == with.width());
debug_assert!(self.height() == with.height());
for (i, other_pixels) in with.chunked().enumerate() {
if other_pixels[3] >= 128 {
// 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
}
}
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 this
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
..(j as usize + 1) * with.width() as usize * 4;
let o_x = ((j as usize + y as usize) * self.width() as usize + x as usize) * 3
..((j as usize + y as usize) * self.width() as usize
+ 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
}
}
impl OverlayAt<Image<&[u8], 3>> for Image<&mut [u8], 3> {
/// Overlay a RGB image(with) => self at coordinates x, y.
/// As this is a `RGBxRGB` operation, blending is unnecessary,
/// and this is simply a copy.
///
/// # Safety
///
/// UB if x, y is out of bounds
#[inline]
unsafe fn overlay_at(&mut self, with: &Image<&[u8], 3>, x: u32, y: u32) -> &mut Self {
/// helper macro for defining rgb=>rgb overlays. allows unrolling
macro_rules! o3x3 {
($n:expr) => {{
for j in 0..($n as usize) {
let i_x = j * ($n as usize) * 3..(j + 1) * ($n as usize) * 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;
// <= because ".." range
debug_assert!(o_x.end <= self.buffer().len());
debug_assert!(i_x.end <= with.buffer().len());
// 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);
}
}};
}
// let it unroll
match with.width() {
8 => o3x3!(8),
16 => o3x3!(16), // this branch makes 8x8 0.16 times slower; but 16x16 0.2 times faster.
_ => o3x3!(with.width()),
}
self
}
}
impl Overlay<Image<&[u8], 4>> for Image<&mut [u8], 3> {
#[inline]
unsafe fn overlay(&mut self, with: &Image<&[u8], 4>) -> &mut Self {
debug_assert!(self.width() == with.width());
debug_assert!(self.height() == with.height());
for (i, chunk) in with
.buffer
.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
}
}
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);
}
}
}
self
}
}