use std::iter::{repeat, StepBy};
use std::ops::Range;
#[inline(always)]
pub fn unpack_bits<F>(buf: &mut [u8], channels: usize, bit_depth: u8, func: F)
where
F: Fn(u8, &mut [u8]),
{
if buf.len() < channels {
return;
}
let bits = buf.len() / channels * bit_depth as usize;
let extra_bits = bits % 8;
let entries = bits / 8
+ match extra_bits {
0 => 0,
_ => 1,
};
let skip = match extra_bits {
0 => 0,
n => (8 - n) / bit_depth as usize,
};
let mask = ((1u16 << bit_depth) - 1) as u8;
let i = (0..entries)
.rev() .flat_map(|idx|
(0..8).step_by(bit_depth.into())
.zip(repeat(idx)))
.skip(skip);
let j = (0..=buf.len() - channels).rev().step_by(channels);
for ((shift, i), j) in i.zip(j) {
let pixel = (buf[i] & (mask << shift)) >> shift;
func(pixel, &mut buf[j..(j + channels)])
}
}
pub fn expand_trns_line(buf: &mut [u8], trns: &[u8], channels: usize) {
if buf.len() < (channels + 1) {
return;
}
let i = (0..=buf.len() / (channels + 1) * channels - channels)
.rev()
.step_by(channels);
let j = (0..=buf.len() - (channels + 1)).rev().step_by(channels + 1);
for (i, j) in i.zip(j) {
let i_pixel = i;
let j_chunk = j;
if &buf[i_pixel..i_pixel + channels] == trns {
buf[j_chunk + channels] = 0
} else {
buf[j_chunk + channels] = 0xFF
}
for k in (0..channels).rev() {
buf[j_chunk + k] = buf[i_pixel + k];
}
}
}
pub fn expand_trns_line16(buf: &mut [u8], trns: &[u8], channels: usize) {
let c2 = 2 * channels;
if buf.len() < (c2 + 2) {
return;
}
let i = (0..=buf.len() / (c2 + 2) * c2 - c2).rev().step_by(c2);
let j = (0..=buf.len() - (c2 + 2)).rev().step_by(c2 + 2);
for (i, j) in i.zip(j) {
let i_pixel = i;
let j_chunk = j;
if &buf[i_pixel..i_pixel + c2] == trns {
buf[j_chunk + c2] = 0;
buf[j_chunk + c2 + 1] = 0
} else {
buf[j_chunk + c2] = 0xFF;
buf[j_chunk + c2 + 1] = 0xFF
}
for k in (0..c2).rev() {
buf[j_chunk + k] = buf[i_pixel + k];
}
}
}
#[derive(Clone)]
pub(crate) struct Adam7Iterator {
line: u32,
lines: u32,
line_width: u32,
current_pass: u8,
width: u32,
height: u32,
}
impl Adam7Iterator {
pub fn new(width: u32, height: u32) -> Adam7Iterator {
let mut this = Adam7Iterator {
line: 0,
lines: 0,
line_width: 0,
current_pass: 1,
width,
height,
};
this.init_pass();
this
}
fn init_pass(&mut self) {
let w = f64::from(self.width);
let h = f64::from(self.height);
let (line_width, lines) = match self.current_pass {
1 => (w / 8.0, h / 8.0),
2 => ((w - 4.0) / 8.0, h / 8.0),
3 => (w / 4.0, (h - 4.0) / 8.0),
4 => ((w - 2.0) / 4.0, h / 4.0),
5 => (w / 2.0, (h - 2.0) / 4.0),
6 => ((w - 1.0) / 2.0, h / 2.0),
7 => (w, (h - 1.0) / 2.0),
_ => unreachable!(),
};
self.line_width = line_width.ceil() as u32;
self.lines = lines.ceil() as u32;
self.line = 0;
}
pub fn current_pass(&self) -> u8 {
self.current_pass
}
}
impl Iterator for Adam7Iterator {
type Item = (u8, u32, u32);
fn next(&mut self) -> Option<Self::Item> {
if self.line < self.lines && self.line_width > 0 {
let this_line = self.line;
self.line += 1;
Some((self.current_pass, this_line, self.line_width))
} else if self.current_pass < 7 {
self.current_pass += 1;
self.init_pass();
self.next()
} else {
None
}
}
}
fn subbyte_pixels(scanline: &[u8], bits_pp: usize) -> impl Iterator<Item = u8> + '_ {
(0..scanline.len() * 8)
.step_by(bits_pp)
.map(move |bit_idx| {
let byte_idx = bit_idx / 8;
let rem = 8 - bit_idx % 8 - bits_pp;
match bits_pp {
1 => (scanline[byte_idx] >> rem) & 1,
2 => (scanline[byte_idx] >> rem) & 3,
4 => (scanline[byte_idx] >> rem) & 15,
_ => unreachable!(),
}
})
}
fn expand_adam7_bits(
pass: u8,
width: usize,
line_no: usize,
bits_pp: usize,
) -> StepBy<Range<usize>> {
let (line_mul, line_off, samp_mul, samp_off) = match pass {
1 => (8, 0, 8, 0),
2 => (8, 0, 8, 4),
3 => (8, 4, 4, 0),
4 => (4, 0, 4, 2),
5 => (4, 2, 2, 0),
6 => (2, 0, 2, 1),
7 => (2, 1, 1, 0),
_ => panic!("Adam7 pass out of range: {}", pass),
};
let prog_line = line_mul * line_no + line_off;
let line_width = (width * bits_pp + 7) & !7;
let line_start = prog_line * line_width;
let start = line_start + (samp_off * bits_pp);
let stop = line_start + (width * bits_pp);
(start..stop).step_by(bits_pp * samp_mul)
}
pub fn expand_pass(
img: &mut [u8],
width: u32,
scanline: &[u8],
pass: u8,
line_no: u32,
bits_pp: u8,
) {
let width = width as usize;
let line_no = line_no as usize;
let bits_pp = bits_pp as usize;
if pass == 0 || pass > 7 {
return;
}
let bit_indices = expand_adam7_bits(pass, width, line_no, bits_pp);
if bits_pp < 8 {
for (pos, px) in bit_indices.zip(subbyte_pixels(scanline, bits_pp)) {
let rem = 8 - pos % 8 - bits_pp;
img[pos / 8] |= px << rem as u8;
}
} else {
let bytes_pp = bits_pp / 8;
for (bitpos, px) in bit_indices.zip(scanline.chunks(bytes_pp)) {
for (offset, val) in px.iter().enumerate() {
img[bitpos / 8 + offset] = *val;
}
}
}
}
#[test]
fn test_adam7() {
let it = Adam7Iterator::new(4, 4);
let passes: Vec<_> = it.collect();
assert_eq!(
&*passes,
&[
(1, 0, 1),
(4, 0, 1),
(5, 0, 2),
(6, 0, 2),
(6, 1, 2),
(7, 0, 4),
(7, 1, 4)
]
);
}
#[test]
fn test_subbyte_pixels() {
let scanline = &[0b10101010, 0b10101010];
let pixels = subbyte_pixels(scanline, 1).collect::<Vec<_>>();
assert_eq!(pixels.len(), 16);
assert_eq!(pixels, [1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0]);
}
#[test]
fn test_expand_adam7_bits() {
let width = 32;
let bits_pp = 1;
let expected = |offset: usize, step: usize, count: usize| {
(0..count)
.map(move |i| step * i + offset)
.collect::<Vec<_>>()
};
for line_no in 0..8 {
let start = 8 * line_no * width;
assert_eq!(
expand_adam7_bits(1, width, line_no, bits_pp).collect::<Vec<_>>(),
expected(start, 8, 4)
);
let start = start + 4;
assert_eq!(
expand_adam7_bits(2, width, line_no, bits_pp).collect::<Vec<_>>(),
expected(start, 8, 4)
);
let start = (8 * line_no + 4) as usize * width as usize;
assert_eq!(
expand_adam7_bits(3, width, line_no, bits_pp).collect::<Vec<_>>(),
expected(start, 4, 8)
);
}
for line_no in 0..16 {
let start = 4 * line_no * width + 2;
assert_eq!(
expand_adam7_bits(4, width, line_no, bits_pp).collect::<Vec<_>>(),
expected(start, 4, 8)
);
let start = (4 * line_no + 2) * width;
assert_eq!(
expand_adam7_bits(5, width, line_no, bits_pp).collect::<Vec<_>>(),
expected(start, 2, 16)
)
}
for line_no in 0..32 {
let start = 2 * line_no * width + 1;
assert_eq!(
expand_adam7_bits(6, width, line_no, bits_pp).collect::<Vec<_>>(),
expected(start, 2, 16),
"line_no: {}",
line_no
);
let start = (2 * line_no + 1) * width;
assert_eq!(
expand_adam7_bits(7, width, line_no, bits_pp).collect::<Vec<_>>(),
expected(start, 1, 32)
);
}
}
#[test]
fn test_expand_pass_subbyte() {
let mut img = [0u8; 8];
let width = 8;
let bits_pp = 1;
expand_pass(&mut img, width, &[0b10000000], 1, 0, bits_pp);
assert_eq!(img, [0b10000000u8, 0, 0, 0, 0, 0, 0, 0]);
expand_pass(&mut img, width, &[0b10000000], 2, 0, bits_pp);
assert_eq!(img, [0b10001000u8, 0, 0, 0, 0, 0, 0, 0]);
expand_pass(&mut img, width, &[0b11000000], 3, 0, bits_pp);
assert_eq!(img, [0b10001000u8, 0, 0, 0, 0b10001000, 0, 0, 0]);
expand_pass(&mut img, width, &[0b11000000], 4, 0, bits_pp);
assert_eq!(img, [0b10101010u8, 0, 0, 0, 0b10001000, 0, 0, 0]);
expand_pass(&mut img, width, &[0b11000000], 4, 1, bits_pp);
assert_eq!(img, [0b10101010u8, 0, 0, 0, 0b10101010, 0, 0, 0]);
expand_pass(&mut img, width, &[0b11110000], 5, 0, bits_pp);
assert_eq!(img, [0b10101010u8, 0, 0b10101010, 0, 0b10101010, 0, 0, 0]);
expand_pass(&mut img, width, &[0b11110000], 5, 1, bits_pp);
assert_eq!(
img,
[0b10101010u8, 0, 0b10101010, 0, 0b10101010, 0, 0b10101010, 0]
);
expand_pass(&mut img, width, &[0b11110000], 6, 0, bits_pp);
assert_eq!(
img,
[0b11111111u8, 0, 0b10101010, 0, 0b10101010, 0, 0b10101010, 0]
);
expand_pass(&mut img, width, &[0b11110000], 6, 1, bits_pp);
assert_eq!(
img,
[0b11111111u8, 0, 0b11111111, 0, 0b10101010, 0, 0b10101010, 0]
);
expand_pass(&mut img, width, &[0b11110000], 6, 2, bits_pp);
assert_eq!(
img,
[0b11111111u8, 0, 0b11111111, 0, 0b11111111, 0, 0b10101010, 0]
);
expand_pass(&mut img, width, &[0b11110000], 6, 3, bits_pp);
assert_eq!(
[0b11111111u8, 0, 0b11111111, 0, 0b11111111, 0, 0b11111111, 0],
img
);
expand_pass(&mut img, width, &[0b11111111], 7, 0, bits_pp);
assert_eq!(
[
0b11111111u8,
0b11111111,
0b11111111,
0,
0b11111111,
0,
0b11111111,
0
],
img
);
expand_pass(&mut img, width, &[0b11111111], 7, 1, bits_pp);
assert_eq!(
[
0b11111111u8,
0b11111111,
0b11111111,
0b11111111,
0b11111111,
0,
0b11111111,
0
],
img
);
expand_pass(&mut img, width, &[0b11111111], 7, 2, bits_pp);
assert_eq!(
[
0b11111111u8,
0b11111111,
0b11111111,
0b11111111,
0b11111111,
0b11111111,
0b11111111,
0
],
img
);
expand_pass(&mut img, width, &[0b11111111], 7, 3, bits_pp);
assert_eq!(
[
0b11111111u8,
0b11111111,
0b11111111,
0b11111111,
0b11111111,
0b11111111,
0b11111111,
0b11111111
],
img
);
}