1use std::cmp::Ordering;
2use std::time::Duration;
3
4use crate::error::ImageResult;
5use crate::RgbaImage;
6
7/// An implementation dependent iterator, reading the frames as requested
8pub struct Frames<'a> {
9 iterator: Box<dyn Iterator<Item = ImageResult<Frame>> + 'a>,
10}
11
12impl<'a> Frames<'a> {
13 /// Creates a new `Frames` from an implementation specific iterator.
14 pub fn new(iterator: Box<dyn Iterator<Item = ImageResult<Frame>> + 'a>) -> Self {
15 Frames { iterator }
16 }
17
18 /// Steps through the iterator from the current frame until the end and pushes each frame into
19 /// a `Vec`.
20 /// If en error is encountered that error is returned instead.
21 ///
22 /// Note: This is equivalent to `Frames::collect::<ImageResult<Vec<Frame>>>()`
23 pub fn collect_frames(self) -> ImageResult<Vec<Frame>> {
24 self.collect()
25 }
26}
27
28impl<'a> Iterator for Frames<'a> {
29 type Item = ImageResult<Frame>;
30 fn next(&mut self) -> Option<ImageResult<Frame>> {
31 self.iterator.next()
32 }
33}
34
35/// A single animation frame
36#[derive(Clone)]
37pub struct Frame {
38 /// Delay between the frames in milliseconds
39 delay: Delay,
40 /// x offset
41 left: u32,
42 /// y offset
43 top: u32,
44 buffer: RgbaImage,
45}
46
47/// The delay of a frame relative to the previous one.
48#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd)]
49pub struct Delay {
50 ratio: Ratio,
51}
52
53impl Frame {
54 /// Constructs a new frame without any delay.
55 pub fn new(buffer: RgbaImage) -> Frame {
56 Frame {
57 delay: Delay::from_ratio(Ratio { numer: 0, denom: 1 }),
58 left: 0,
59 top: 0,
60 buffer,
61 }
62 }
63
64 /// Constructs a new frame
65 pub fn from_parts(buffer: RgbaImage, left: u32, top: u32, delay: Delay) -> Frame {
66 Frame {
67 delay,
68 left,
69 top,
70 buffer,
71 }
72 }
73
74 /// Delay of this frame
75 pub fn delay(&self) -> Delay {
76 self.delay
77 }
78
79 /// Returns the image buffer
80 pub fn buffer(&self) -> &RgbaImage {
81 &self.buffer
82 }
83
84 /// Returns a mutable image buffer
85 pub fn buffer_mut(&mut self) -> &mut RgbaImage {
86 &mut self.buffer
87 }
88
89 /// Returns the image buffer
90 pub fn into_buffer(self) -> RgbaImage {
91 self.buffer
92 }
93
94 /// Returns the x offset
95 pub fn left(&self) -> u32 {
96 self.left
97 }
98
99 /// Returns the y offset
100 pub fn top(&self) -> u32 {
101 self.top
102 }
103}
104
105impl Delay {
106 /// Create a delay from a ratio of milliseconds.
107 ///
108 /// # Examples
109 ///
110 /// ```
111 /// use image::Delay;
112 /// let delay_10ms = Delay::from_numer_denom_ms(10, 1);
113 /// ```
114 pub fn from_numer_denom_ms(numerator: u32, denominator: u32) -> Self {
115 Delay {
116 ratio: Ratio::new(numerator, denominator),
117 }
118 }
119
120 /// Convert from a duration, clamped between 0 and an implemented defined maximum.
121 ///
122 /// The maximum is *at least* `i32::MAX` milliseconds. It should be noted that the accuracy of
123 /// the result may be relative and very large delays have a coarse resolution.
124 ///
125 /// # Examples
126 ///
127 /// ```
128 /// use std::time::Duration;
129 /// use image::Delay;
130 ///
131 /// let duration = Duration::from_millis(20);
132 /// let delay = Delay::from_saturating_duration(duration);
133 /// ```
134 pub fn from_saturating_duration(duration: Duration) -> Self {
135 // A few notes: The largest number we can represent as a ratio is u32::MAX but we can
136 // sometimes represent much smaller numbers.
137 //
138 // We can represent duration as `millis+a/b` (where a < b, b > 0).
139 // We must thus bound b with `b·millis + (b-1) <= u32::MAX` or
140 // > `0 < b <= (u32::MAX + 1)/(millis + 1)`
141 // Corollary: millis <= u32::MAX
142
143 const MILLIS_BOUND: u128 = u32::max_value() as u128;
144
145 let millis = duration.as_millis().min(MILLIS_BOUND);
146 let submillis = (duration.as_nanos() % 1_000_000) as u32;
147
148 let max_b = if millis > 0 {
149 ((MILLIS_BOUND + 1) / (millis + 1)) as u32
150 } else {
151 MILLIS_BOUND as u32
152 };
153 let millis = millis as u32;
154
155 let (a, b) = Self::closest_bounded_fraction(max_b, submillis, 1_000_000);
156 Self::from_numer_denom_ms(a + b * millis, b)
157 }
158
159 /// The numerator and denominator of the delay in milliseconds.
160 ///
161 /// This is guaranteed to be an exact conversion if the `Delay` was previously created with the
162 /// `from_numer_denom_ms` constructor.
163 pub fn numer_denom_ms(self) -> (u32, u32) {
164 (self.ratio.numer, self.ratio.denom)
165 }
166
167 pub(crate) fn from_ratio(ratio: Ratio) -> Self {
168 Delay { ratio }
169 }
170
171 pub(crate) fn into_ratio(self) -> Ratio {
172 self.ratio
173 }
174
175 /// Given some fraction, compute an approximation with denominator bounded.
176 ///
177 /// Note that `denom_bound` bounds nominator and denominator of all intermediate
178 /// approximations and the end result.
179 fn closest_bounded_fraction(denom_bound: u32, nom: u32, denom: u32) -> (u32, u32) {
180 use std::cmp::Ordering::*;
181 assert!(0 < denom);
182 assert!(0 < denom_bound);
183 assert!(nom < denom);
184
185 // Avoid a few type troubles. All intermediate results are bounded by `denom_bound` which
186 // is in turn bounded by u32::MAX. Representing with u64 allows multiplication of any two
187 // values without fears of overflow.
188
189 // Compare two fractions whose parts fit into a u32.
190 fn compare_fraction((an, ad): (u64, u64), (bn, bd): (u64, u64)) -> Ordering {
191 (an * bd).cmp(&(bn * ad))
192 }
193
194 // Computes the nominator of the absolute difference between two such fractions.
195 fn abs_diff_nom((an, ad): (u64, u64), (bn, bd): (u64, u64)) -> u64 {
196 let c0 = an * bd;
197 let c1 = ad * bn;
198
199 let d0 = c0.max(c1);
200 let d1 = c0.min(c1);
201 d0 - d1
202 }
203
204 let exact = (u64::from(nom), u64::from(denom));
205 // The lower bound fraction, numerator and denominator.
206 let mut lower = (0u64, 1u64);
207 // The upper bound fraction, numerator and denominator.
208 let mut upper = (1u64, 1u64);
209 // The closest approximation for now.
210 let mut guess = (u64::from(nom * 2 > denom), 1u64);
211
212 // loop invariant: ad, bd <= denom_bound
213 // iterates the Farey sequence.
214 loop {
215 // Break if we are done.
216 if compare_fraction(guess, exact) == Equal {
217 break;
218 }
219
220 // Break if next Farey number is out-of-range.
221 if u64::from(denom_bound) - lower.1 < upper.1 {
222 break;
223 }
224
225 // Next Farey approximation n between a and b
226 let next = (lower.0 + upper.0, lower.1 + upper.1);
227 // if F < n then replace the upper bound, else replace lower.
228 if compare_fraction(exact, next) == Less {
229 upper = next;
230 } else {
231 lower = next;
232 }
233
234 // Now correct the closest guess.
235 // In other words, if |c - f| > |n - f| then replace it with the new guess.
236 // This favors the guess with smaller denominator on equality.
237
238 // |g - f| = |g_diff_nom|/(gd*fd);
239 let g_diff_nom = abs_diff_nom(guess, exact);
240 // |n - f| = |n_diff_nom|/(nd*fd);
241 let n_diff_nom = abs_diff_nom(next, exact);
242
243 // The difference |n - f| is smaller than |g - f| if either the integral part of the
244 // fraction |n_diff_nom|/nd is smaller than the one of |g_diff_nom|/gd or if they are
245 // the same but the fractional part is larger.
246 if match (n_diff_nom / next.1).cmp(&(g_diff_nom / guess.1)) {
247 Less => true,
248 Greater => false,
249 // Note that the nominator for the fractional part is smaller than its denominator
250 // which is smaller than u32 and can't overflow the multiplication with the other
251 // denominator, that is we can compare these fractions by multiplication with the
252 // respective other denominator.
253 Equal => {
254 compare_fraction(
255 (n_diff_nom % next.1, next.1),
256 (g_diff_nom % guess.1, guess.1),
257 ) == Less
258 }
259 } {
260 guess = next;
261 }
262 }
263
264 (guess.0 as u32, guess.1 as u32)
265 }
266}
267
268impl From<Delay> for Duration {
269 fn from(delay: Delay) -> Self {
270 let ratio: Ratio = delay.into_ratio();
271 let ms: u32 = ratio.to_integer();
272 let rest: u32 = ratio.numer % ratio.denom;
273 let nanos: u64 = (u64::from(rest) * 1_000_000) / u64::from(ratio.denom);
274 Duration::from_millis(ms.into()) + Duration::from_nanos(nanos)
275 }
276}
277
278#[derive(Copy, Clone, Debug)]
279pub(crate) struct Ratio {
280 numer: u32,
281 denom: u32,
282}
283
284impl Ratio {
285 #[inline]
286 pub(crate) fn new(numerator: u32, denominator: u32) -> Self {
287 assert_ne!(denominator, 0);
288 Self {
289 numer: numerator,
290 denom: denominator,
291 }
292 }
293
294 #[inline]
295 pub(crate) fn to_integer(&self) -> u32 {
296 self.numer / self.denom
297 }
298}
299
300impl PartialEq for Ratio {
301 fn eq(&self, other: &Self) -> bool {
302 self.cmp(other) == Ordering::Equal
303 }
304}
305
306impl Eq for Ratio {}
307
308impl PartialOrd for Ratio {
309 fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
310 Some(self.cmp(other))
311 }
312}
313
314impl Ord for Ratio {
315 fn cmp(&self, other: &Self) -> Ordering {
316 // The following comparison can be simplified:
317 // a / b <cmp> c / d
318 // We multiply both sides by `b`:
319 // a <cmp> c * b / d
320 // We multiply both sides by `d`:
321 // a * d <cmp> c * b
322
323 let a: u32 = self.numer;
324 let b: u32 = self.denom;
325 let c: u32 = other.numer;
326 let d: u32 = other.denom;
327
328 // We cast the types from `u32` to `u64` in order
329 // to not overflow the multiplications.
330
331 (a as u64 * d as u64).cmp(&(c as u64 * b as u64))
332 }
333}
334
335#[cfg(test)]
336mod tests {
337 use super::{Delay, Duration, Ratio};
338
339 #[test]
340 fn simple() {
341 let second = Delay::from_numer_denom_ms(1000, 1);
342 assert_eq!(Duration::from(second), Duration::from_secs(1));
343 }
344
345 #[test]
346 fn fps_30() {
347 let thirtieth = Delay::from_numer_denom_ms(1000, 30);
348 let duration = Duration::from(thirtieth);
349 assert_eq!(duration.as_secs(), 0);
350 assert_eq!(duration.subsec_millis(), 33);
351 assert_eq!(duration.subsec_nanos(), 33_333_333);
352 }
353
354 #[test]
355 fn duration_outlier() {
356 let oob = Duration::from_secs(0xFFFF_FFFF);
357 let delay = Delay::from_saturating_duration(oob);
358 assert_eq!(delay.numer_denom_ms(), (0xFFFF_FFFF, 1));
359 }
360
361 #[test]
362 fn duration_approx() {
363 let oob = Duration::from_millis(0xFFFF_FFFF) + Duration::from_micros(1);
364 let delay = Delay::from_saturating_duration(oob);
365 assert_eq!(delay.numer_denom_ms(), (0xFFFF_FFFF, 1));
366
367 let inbounds = Duration::from_millis(0xFFFF_FFFF) - Duration::from_micros(1);
368 let delay = Delay::from_saturating_duration(inbounds);
369 assert_eq!(delay.numer_denom_ms(), (0xFFFF_FFFF, 1));
370
371 let fine =
372 Duration::from_millis(0xFFFF_FFFF / 1000) + Duration::from_micros(0xFFFF_FFFF % 1000);
373 let delay = Delay::from_saturating_duration(fine);
374 // Funnily, 0xFFFF_FFFF is divisble by 5, thus we compare with a `Ratio`.
375 assert_eq!(delay.into_ratio(), Ratio::new(0xFFFF_FFFF, 1000));
376 }
377
378 #[test]
379 fn precise() {
380 // The ratio has only 32 bits in the numerator, too imprecise to get more than 11 digits
381 // correct. But it may be expressed as 1_000_000/3 instead.
382 let exceed = Duration::from_secs(333) + Duration::from_nanos(333_333_333);
383 let delay = Delay::from_saturating_duration(exceed);
384 assert_eq!(Duration::from(delay), exceed);
385 }
386
387 #[test]
388 fn small() {
389 // Not quite a delay of `1 ms`.
390 let delay = Delay::from_numer_denom_ms(1 << 16, (1 << 16) + 1);
391 let duration = Duration::from(delay);
392 assert_eq!(duration.as_millis(), 0);
393 // Not precisely the original but should be smaller than 0.
394 let delay = Delay::from_saturating_duration(duration);
395 assert_eq!(delay.into_ratio().to_integer(), 0);
396 }
397}
398