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use std::{marker::PhantomData, num::NonZeroU32};
use crate::Image;
/// A smaller part of a larger image.
///
/// ```text
/// ┏━━━━━━━━━━━━━━┓ hard borders represent the full image
/// ┃ 1 2 3 1 ┃ vvvv the top left of the new image
/// ┃ ┌──────┐ ┃ crop(2, 2).from(1, 1)
/// ┃ 4 │ 5 6 │ 2 ┃ ^^^^ width and height
/// ┃ │ │ ┃
/// ┃ 7 │ 8 9 │ 3 ┃
/// ┗━━━┷━━━━━━┷━━━┛ soft borders represent the new image
/// ```
#[derive(Clone)]
pub struct SubImage<T, const CHANNELS: usize> {
inner: Image<T, CHANNELS>,
/// in pixels
offset_x: u32,
real_width: NonZeroU32,
real_height: NonZeroU32,
}
/// Trait for cropping a image.
pub trait Cropper<T, const C: usize> {
/// # Panics
///
/// if w - y == 0
fn from(self, x: u32, y: u32) -> SubImage<T, C>;
}
impl<T: Clone, const N: usize> Copy for SubImage<T, N> where Image<T, N>: Copy {}
macro_rules! def {
($t:ty, $($what:ident)?) => {
struct Crop<'a, T, const C: usize> {
dimensions: (NonZeroU32, NonZeroU32),
_d: PhantomData<SubImage<$t, C>>,
image: Image<$t, C>,
}
impl<'a, T, const C: usize> Cropper<$t, C> for Crop<'a, T, C> {
fn from(self, x: u32, y: u32) -> SubImage<$t, C> {
let w = self.image.width();
// SAFETY: ctor
let i = unsafe {
Image::new(
self.image.width,
NonZeroU32::new(self.image.height() - y).unwrap(),
&$($what)?(self.image.take_buffer()[(y as usize * C) * w as usize..]),
)
};
SubImage {
offset_x: x,
inner: i,
real_width: self.dimensions.0,
real_height: self.dimensions.1,
}
}
}
};
}
impl<T, const C: usize> Image<T, C> {
/// Crop a image.
///
/// The signature looks something like: `i.crop(width, height).from(top_left_x, top_left_y)`, which gives you a <code>[SubImage]<&\[T\], _></code>
///
/// If you want a owned image, `i.crop(w, h).from(x, y).own()` gets you a <code>[`Image`]<[Box]<\[T\], _>></code> back.
///
/// ```
/// # use fimg::{Image, Cropper};
/// let mut i = Image::<_, 1>::build(4, 3).buf([
/// 1, 2, 3, 1,
/// 4, 5, 6, 2,
/// 7, 8, 9, 3,
/// ]);
/// let c = i.crop(2, 2).from(1, 1);
/// # unsafe {
/// assert_eq!(c.pixel(0, 0), [5]);
/// assert_eq!(c.pixel(1, 1), [9]);
/// assert_eq!(
/// c.own().bytes(),
/// &[5, 6,
/// 8, 9]
/// );
/// # }
/// ```
///
/// # Panics
///
/// if width == 0 || height == 0
pub fn crop<'a, U: 'a>(&'a self, width: u32, height: u32) -> impl Cropper<&'a [U], C>
where
T: AsRef<[U]>,
{
def!(&'a [T],);
Crop {
dimensions: (
NonZeroU32::new(width).expect("Image::crop panics when width == 0"),
NonZeroU32::new(height).expect("Image::crop panics when height == 0"),
),
_d: PhantomData,
image: self.as_ref(),
}
}
/// Like [`Image::crop`], but returns a mutable [`SubImage`].
pub fn crop_mut<'a, U: 'a>(
&'a mut self,
width: u32,
height: u32,
) -> impl Cropper<&'a mut [U], C>
where
T: AsMut<[U]> + AsRef<[U]>,
{
def!(&'a mut [T], mut);
Crop {
dimensions: (
NonZeroU32::new(width).expect("Image::crop panics when width == 0"),
NonZeroU32::new(height).expect("Image::crop panics when height == 0"),
),
_d: PhantomData,
image: self.as_mut(),
}
}
}
impl<T: Clone, const C: usize> SubImage<&[T], C> {
/// Clones this [`SubImage`] into its own [`Image`]
pub fn own(&self) -> Image<Box<[T]>, C> {
let mut out = Vec::with_capacity(
self.real_width.get() as usize * self.real_height.get() as usize * C,
);
for row in self.inner.rows().take(self.real_height.get() as usize) {
out.extend_from_slice(
&row[self.offset_x as usize
..self.offset_x as usize + self.real_width.get() as usize]
.as_flattened(),
);
}
// SAFETY: ctor
unsafe { Image::new(self.real_width, self.real_height, out.into()) }
}
}
// TODO crop()
impl<W, const C: usize> SubImage<W, C> {
/// Get a pixel.
///
/// # Safety
///
/// this pixel must be in bounds.
pub unsafe fn pixel<U: Copy>(&self, x: u32, y: u32) -> &[U; C]
where
W: AsRef<[U]>,
{
// note: if you get a pixel, in release mode, that is in bounds of the outer image, but not the sub image, that would be library-ub.
debug_assert!(x < self.real_width.get());
debug_assert!(y < self.real_height.get());
// SAFETY: caller
unsafe { self.inner.pixel(x + self.offset_x, y) }
}
/// Get a pixel, mutably.
///
/// # Safety
///
/// this pixel must be in bounds.
pub unsafe fn pixel_mut<U: Copy>(&mut self, x: u32, y: u32) -> &mut [U]
where
W: AsMut<[U]> + AsRef<[U]>,
{
debug_assert!(x < self.real_width.get());
debug_assert!(y < self.real_height.get());
// SAFETY: caller
unsafe { self.inner.pixel_mut(x, y) }
}
}