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use std::cmp::Ordering;
use std::time::Duration;
use crate::error::ImageResult;
use crate::RgbaImage;
/// An implementation dependent iterator, reading the frames as requested
pub struct Frames<'a> {
iterator: Box<dyn Iterator<Item = ImageResult<Frame>> + 'a>,
}
impl<'a> Frames<'a> {
/// Creates a new `Frames` from an implementation specific iterator.
pub fn new(iterator: Box<dyn Iterator<Item = ImageResult<Frame>> + 'a>) -> Self {
Frames { iterator }
}
/// Steps through the iterator from the current frame until the end and pushes each frame into
/// a `Vec`.
/// If en error is encountered that error is returned instead.
///
/// Note: This is equivalent to `Frames::collect::<ImageResult<Vec<Frame>>>()`
pub fn collect_frames(self) -> ImageResult<Vec<Frame>> {
self.collect()
}
}
impl<'a> Iterator for Frames<'a> {
type Item = ImageResult<Frame>;
fn next(&mut self) -> Option<ImageResult<Frame>> {
self.iterator.next()
}
}
/// A single animation frame
#[derive(Clone)]
pub struct Frame {
/// Delay between the frames in milliseconds
delay: Delay,
/// x offset
left: u32,
/// y offset
top: u32,
buffer: RgbaImage,
}
/// The delay of a frame relative to the previous one.
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd)]
pub struct Delay {
ratio: Ratio,
}
impl Frame {
/// Constructs a new frame without any delay.
pub fn new(buffer: RgbaImage) -> Frame {
Frame {
delay: Delay::from_ratio(Ratio { numer: 0, denom: 1 }),
left: 0,
top: 0,
buffer,
}
}
/// Constructs a new frame
pub fn from_parts(buffer: RgbaImage, left: u32, top: u32, delay: Delay) -> Frame {
Frame {
delay,
left,
top,
buffer,
}
}
/// Delay of this frame
pub fn delay(&self) -> Delay {
self.delay
}
/// Returns the image buffer
pub fn buffer(&self) -> &RgbaImage {
&self.buffer
}
/// Returns a mutable image buffer
pub fn buffer_mut(&mut self) -> &mut RgbaImage {
&mut self.buffer
}
/// Returns the image buffer
pub fn into_buffer(self) -> RgbaImage {
self.buffer
}
/// Returns the x offset
pub fn left(&self) -> u32 {
self.left
}
/// Returns the y offset
pub fn top(&self) -> u32 {
self.top
}
}
impl Delay {
/// Create a delay from a ratio of milliseconds.
///
/// # Examples
///
/// ```
/// use image::Delay;
/// let delay_10ms = Delay::from_numer_denom_ms(10, 1);
/// ```
pub fn from_numer_denom_ms(numerator: u32, denominator: u32) -> Self {
Delay {
ratio: Ratio::new(numerator, denominator),
}
}
/// Convert from a duration, clamped between 0 and an implemented defined maximum.
///
/// The maximum is *at least* `i32::MAX` milliseconds. It should be noted that the accuracy of
/// the result may be relative and very large delays have a coarse resolution.
///
/// # Examples
///
/// ```
/// use std::time::Duration;
/// use image::Delay;
///
/// let duration = Duration::from_millis(20);
/// let delay = Delay::from_saturating_duration(duration);
/// ```
pub fn from_saturating_duration(duration: Duration) -> Self {
// A few notes: The largest number we can represent as a ratio is u32::MAX but we can
// sometimes represent much smaller numbers.
//
// We can represent duration as `millis+a/b` (where a < b, b > 0).
// We must thus bound b with `bĀ·millis + (b-1) <= u32::MAX` or
// > `0 < b <= (u32::MAX + 1)/(millis + 1)`
// Corollary: millis <= u32::MAX
const MILLIS_BOUND: u128 = u32::max_value() as u128;
let millis = duration.as_millis().min(MILLIS_BOUND);
let submillis = (duration.as_nanos() % 1_000_000) as u32;
let max_b = if millis > 0 {
((MILLIS_BOUND + 1) / (millis + 1)) as u32
} else {
MILLIS_BOUND as u32
};
let millis = millis as u32;
let (a, b) = Self::closest_bounded_fraction(max_b, submillis, 1_000_000);
Self::from_numer_denom_ms(a + b * millis, b)
}
/// The numerator and denominator of the delay in milliseconds.
///
/// This is guaranteed to be an exact conversion if the `Delay` was previously created with the
/// `from_numer_denom_ms` constructor.
pub fn numer_denom_ms(self) -> (u32, u32) {
(self.ratio.numer, self.ratio.denom)
}
pub(crate) fn from_ratio(ratio: Ratio) -> Self {
Delay { ratio }
}
pub(crate) fn into_ratio(self) -> Ratio {
self.ratio
}
/// Given some fraction, compute an approximation with denominator bounded.
///
/// Note that `denom_bound` bounds nominator and denominator of all intermediate
/// approximations and the end result.
fn closest_bounded_fraction(denom_bound: u32, nom: u32, denom: u32) -> (u32, u32) {
use std::cmp::Ordering::*;
assert!(0 < denom);
assert!(0 < denom_bound);
assert!(nom < denom);
// Avoid a few type troubles. All intermediate results are bounded by `denom_bound` which
// is in turn bounded by u32::MAX. Representing with u64 allows multiplication of any two
// values without fears of overflow.
// Compare two fractions whose parts fit into a u32.
fn compare_fraction((an, ad): (u64, u64), (bn, bd): (u64, u64)) -> Ordering {
(an * bd).cmp(&(bn * ad))
}
// Computes the nominator of the absolute difference between two such fractions.
fn abs_diff_nom((an, ad): (u64, u64), (bn, bd): (u64, u64)) -> u64 {
let c0 = an * bd;
let c1 = ad * bn;
let d0 = c0.max(c1);
let d1 = c0.min(c1);
d0 - d1
}
let exact = (u64::from(nom), u64::from(denom));
// The lower bound fraction, numerator and denominator.
let mut lower = (0u64, 1u64);
// The upper bound fraction, numerator and denominator.
let mut upper = (1u64, 1u64);
// The closest approximation for now.
let mut guess = (u64::from(nom * 2 > denom), 1u64);
// loop invariant: ad, bd <= denom_bound
// iterates the Farey sequence.
loop {
// Break if we are done.
if compare_fraction(guess, exact) == Equal {
break;
}
// Break if next Farey number is out-of-range.
if u64::from(denom_bound) - lower.1 < upper.1 {
break;
}
// Next Farey approximation n between a and b
let next = (lower.0 + upper.0, lower.1 + upper.1);
// if F < n then replace the upper bound, else replace lower.
if compare_fraction(exact, next) == Less {
upper = next;
} else {
lower = next;
}
// Now correct the closest guess.
// In other words, if |c - f| > |n - f| then replace it with the new guess.
// This favors the guess with smaller denominator on equality.
// |g - f| = |g_diff_nom|/(gd*fd);
let g_diff_nom = abs_diff_nom(guess, exact);
// |n - f| = |n_diff_nom|/(nd*fd);
let n_diff_nom = abs_diff_nom(next, exact);
// The difference |n - f| is smaller than |g - f| if either the integral part of the
// fraction |n_diff_nom|/nd is smaller than the one of |g_diff_nom|/gd or if they are
// the same but the fractional part is larger.
if match (n_diff_nom / next.1).cmp(&(g_diff_nom / guess.1)) {
Less => true,
Greater => false,
// Note that the nominator for the fractional part is smaller than its denominator
// which is smaller than u32 and can't overflow the multiplication with the other
// denominator, that is we can compare these fractions by multiplication with the
// respective other denominator.
Equal => {
compare_fraction(
(n_diff_nom % next.1, next.1),
(g_diff_nom % guess.1, guess.1),
) == Less
}
} {
guess = next;
}
}
(guess.0 as u32, guess.1 as u32)
}
}
impl From<Delay> for Duration {
fn from(delay: Delay) -> Self {
let ratio = delay.into_ratio();
let ms = ratio.to_integer();
let rest = ratio.numer % ratio.denom;
let nanos = (u64::from(rest) * 1_000_000) / u64::from(ratio.denom);
Duration::from_millis(ms.into()) + Duration::from_nanos(nanos)
}
}
#[derive(Copy, Clone, Debug)]
pub(crate) struct Ratio {
numer: u32,
denom: u32,
}
impl Ratio {
#[inline]
pub(crate) fn new(numerator: u32, denominator: u32) -> Self {
assert_ne!(denominator, 0);
Self {
numer: numerator,
denom: denominator,
}
}
#[inline]
pub(crate) fn to_integer(&self) -> u32 {
self.numer / self.denom
}
}
impl PartialEq for Ratio {
fn eq(&self, other: &Self) -> bool {
self.cmp(other) == Ordering::Equal
}
}
impl Eq for Ratio {}
impl PartialOrd for Ratio {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl Ord for Ratio {
fn cmp(&self, other: &Self) -> Ordering {
// The following comparison can be simplified:
// a / b <cmp> c / d
// We multiply both sides by `b`:
// a <cmp> c * b / d
// We multiply both sides by `d`:
// a * d <cmp> c * b
let a: u32 = self.numer;
let b: u32 = self.denom;
let c: u32 = other.numer;
let d: u32 = other.denom;
// We cast the types from `u32` to `u64` in order
// to not overflow the multiplications.
(a as u64 * d as u64).cmp(&(c as u64 * b as u64))
}
}
#[cfg(test)]
mod tests {
use super::{Delay, Duration, Ratio};
#[test]
fn simple() {
let second = Delay::from_numer_denom_ms(1000, 1);
assert_eq!(Duration::from(second), Duration::from_secs(1));
}
#[test]
fn fps_30() {
let thirtieth = Delay::from_numer_denom_ms(1000, 30);
let duration = Duration::from(thirtieth);
assert_eq!(duration.as_secs(), 0);
assert_eq!(duration.subsec_millis(), 33);
assert_eq!(duration.subsec_nanos(), 33_333_333);
}
#[test]
fn duration_outlier() {
let oob = Duration::from_secs(0xFFFF_FFFF);
let delay = Delay::from_saturating_duration(oob);
assert_eq!(delay.numer_denom_ms(), (0xFFFF_FFFF, 1));
}
#[test]
fn duration_approx() {
let oob = Duration::from_millis(0xFFFF_FFFF) + Duration::from_micros(1);
let delay = Delay::from_saturating_duration(oob);
assert_eq!(delay.numer_denom_ms(), (0xFFFF_FFFF, 1));
let inbounds = Duration::from_millis(0xFFFF_FFFF) - Duration::from_micros(1);
let delay = Delay::from_saturating_duration(inbounds);
assert_eq!(delay.numer_denom_ms(), (0xFFFF_FFFF, 1));
let fine =
Duration::from_millis(0xFFFF_FFFF / 1000) + Duration::from_micros(0xFFFF_FFFF % 1000);
let delay = Delay::from_saturating_duration(fine);
// Funnily, 0xFFFF_FFFF is divisble by 5, thus we compare with a `Ratio`.
assert_eq!(delay.into_ratio(), Ratio::new(0xFFFF_FFFF, 1000));
}
#[test]
fn precise() {
// The ratio has only 32 bits in the numerator, too imprecise to get more than 11 digits
// correct. But it may be expressed as 1_000_000/3 instead.
let exceed = Duration::from_secs(333) + Duration::from_nanos(333_333_333);
let delay = Delay::from_saturating_duration(exceed);
assert_eq!(Duration::from(delay), exceed);
}
#[test]
fn small() {
// Not quite a delay of `1 ms`.
let delay = Delay::from_numer_denom_ms(1 << 16, (1 << 16) + 1);
let duration = Duration::from(delay);
assert_eq!(duration.as_millis(), 0);
// Not precisely the original but should be smaller than 0.
let delay = Delay::from_saturating_duration(duration);
assert_eq!(delay.into_ratio().to_integer(), 0);
}
}