exr/block/
samples.rs

1//! Extract pixel samples from a block of pixel bytes.
2
3use crate::prelude::*;
4use half::prelude::HalfFloatSliceExt;
5
6
7/// A single red, green, blue, or alpha value.
8#[derive(Copy, Clone, Debug)]
9pub enum Sample {
10
11    /// A 16-bit float sample.
12    F16(f16),
13
14    /// A 32-bit float sample.
15    F32(f32),
16
17    /// An unsigned integer sample.
18    U32(u32)
19}
20
21impl Sample {
22
23    /// Create a sample containing a 32-bit float.
24    pub fn f32(f32: f32) -> Self { Sample::F32(f32) }
25
26    /// Create a sample containing a 16-bit float.
27    pub fn f16(f16: f16) -> Self { Sample::F16(f16) }
28
29    /// Create a sample containing a 32-bit integer.
30    pub fn u32(u32: u32) -> Self { Sample::U32(u32) }
31
32    /// Convert the sample to an f16 value. This has lower precision than f32.
33    /// Note: An f32 can only represent integers up to `1024` as precise as a u32 could.
34    #[inline]
35    pub fn to_f16(self) -> f16 {
36        match self {
37            Sample::F16(sample) => sample,
38            Sample::F32(sample) => f16::from_f32(sample),
39            Sample::U32(sample) => f16::from_f32(sample as f32),
40        }
41    }
42
43    /// Convert the sample to an f32 value.
44    /// Note: An f32 can only represent integers up to `8388608` as precise as a u32 could.
45    #[inline]
46    pub fn to_f32(self) -> f32 {
47        match self {
48            Sample::F32(sample) => sample,
49            Sample::F16(sample) => sample.to_f32(),
50            Sample::U32(sample) => sample as f32,
51        }
52    }
53
54    /// Convert the sample to a u32. Rounds floats to integers the same way that `3.1 as u32` does.
55    #[inline]
56    pub fn to_u32(self) -> u32 {
57        match self {
58            Sample::F16(sample) => sample.to_f32() as u32,
59            Sample::F32(sample) => sample as u32,
60            Sample::U32(sample) => sample,
61        }
62    }
63
64    /// Is this value not a number?
65    #[inline]
66    pub fn is_nan(self) -> bool {
67        match self {
68            Sample::F16(value) => value.is_nan(),
69            Sample::F32(value) => value.is_nan(),
70            Sample::U32(_) => false,
71        }
72    }
73
74    /// Is this value zero or negative zero?
75    #[inline]
76    pub fn is_zero(&self) -> bool {
77        match *self {
78            Sample::F16(value) => value == f16::ZERO || value == f16::NEG_ZERO,
79            Sample::F32(value) => value == 0.0,
80            Sample::U32(value) => value == 0,
81        }
82    }
83}
84
85impl PartialEq for Sample {
86    fn eq(&self, other: &Self) -> bool {
87        match *self {
88            Sample::F16(num) => num == other.to_f16(),
89            Sample::F32(num) => num == other.to_f32(),
90            Sample::U32(num) => num == other.to_u32(),
91        }
92    }
93}
94
95// this is not recommended because it may hide whether a color is transparent or opaque and might be undesired for depth channels
96impl Default for Sample {
97    fn default() -> Self { Sample::F32(0.0) }
98}
99
100impl From<f16> for Sample { #[inline] fn from(f: f16) -> Self { Sample::F16(f) } }
101impl From<f32> for Sample { #[inline] fn from(f: f32) -> Self { Sample::F32(f) } }
102impl From<u32> for Sample { #[inline] fn from(f: u32) -> Self { Sample::U32(f) } }
103
104impl<T> From<Option<T>> for Sample where T: Into<Sample> + Default {
105    #[inline] fn from(num: Option<T>) -> Self { num.unwrap_or_default().into() }
106}
107
108
109impl From<Sample> for f16 { #[inline] fn from(s: Sample) -> Self { s.to_f16() } }
110impl From<Sample> for f32 { #[inline] fn from(s: Sample) -> Self { s.to_f32() } }
111impl From<Sample> for u32 { #[inline] fn from(s: Sample) -> Self { s.to_u32() } }
112
113
114/// Create an arbitrary sample type from one of the defined sample types.
115/// Should be compiled to a no-op where the file contains the predicted sample type.
116/// The slice functions should be optimized into a `memcpy` where there is no conversion needed.
117pub trait FromNativeSample: Sized + Copy + Default + 'static {
118
119    /// Create this sample from a f16, trying to represent the same numerical value
120    fn from_f16(value: f16) -> Self;
121
122    /// Create this sample from a f32, trying to represent the same numerical value
123    fn from_f32(value: f32) -> Self;
124
125    /// Create this sample from a u32, trying to represent the same numerical value
126    fn from_u32(value: u32) -> Self;
127
128    /// Convert all values from the slice into this type.
129    /// This function exists to allow the compiler to perform a vectorization optimization.
130    /// Note that this default implementation will **not** be vectorized by the compiler automatically.
131    /// For maximum performance you will need to override this function and implement it via
132    /// an explicit batched conversion such as [`convert_to_f32_slice`](https://docs.rs/half/2.3.1/half/slice/trait.HalfFloatSliceExt.html#tymethod.convert_to_f32_slice)
133    #[inline]
134    fn from_f16s(from: &[f16], to: &mut [Self]) {
135        assert_eq!(from.len(), to.len(), "slices must have the same length");
136        for (from, to) in from.iter().zip(to.iter_mut()) {
137            *to = Self::from_f16(*from);
138        }
139    }
140
141    /// Convert all values from the slice into this type.
142    /// This function exists to allow the compiler to perform a vectorization optimization.
143    /// Note that this default implementation will be vectorized by the compiler automatically.
144    #[inline]
145    fn from_f32s(from: &[f32], to: &mut [Self]) {
146        assert_eq!(from.len(), to.len(), "slices must have the same length");
147        for (from, to) in from.iter().zip(to.iter_mut()) {
148            *to = Self::from_f32(*from);
149        }
150    }
151
152    /// Convert all values from the slice into this type.
153    /// This function exists to allow the compiler to perform a vectorization optimization.
154    /// Note that this default implementation will be vectorized by the compiler automatically,
155    /// provided that the CPU supports the necessary conversion instructions.
156    /// For example, x86_64 lacks the instructions to convert `u32` to floats,
157    /// so this will inevitably be slow on x86_64.
158    #[inline]
159    fn from_u32s(from: &[u32], to: &mut [Self]) {
160        assert_eq!(from.len(), to.len(), "slices must have the same length");
161        for (from, to) in from.iter().zip(to.iter_mut()) {
162            *to = Self::from_u32(*from);
163        }
164    }
165}
166
167// TODO haven't i implemented this exact behaviour already somewhere else in this library...??
168impl FromNativeSample for f32 {
169    #[inline] fn from_f16(value: f16) -> Self { value.to_f32() }
170    #[inline] fn from_f32(value: f32) -> Self { value }
171    #[inline] fn from_u32(value: u32) -> Self { value as f32 }
172
173    // f16 is a custom type
174    // so the compiler can not automatically vectorize the conversion
175    // that's why we need to specialize this function
176    #[inline]
177    fn from_f16s(from: &[f16], to: &mut [Self]) {
178        from.convert_to_f32_slice(to);
179    }
180}
181
182impl FromNativeSample for u32 {
183    #[inline] fn from_f16(value: f16) -> Self { value.to_f32() as u32 }
184    #[inline] fn from_f32(value: f32) -> Self { value as u32 }
185    #[inline] fn from_u32(value: u32) -> Self { value }
186}
187
188impl FromNativeSample for f16 {
189    #[inline] fn from_f16(value: f16) -> Self { value }
190    #[inline] fn from_f32(value: f32) -> Self { f16::from_f32(value) }
191    #[inline] fn from_u32(value: u32) -> Self { f16::from_f32(value as f32) }
192
193    // f16 is a custom type
194    // so the compiler can not automatically vectorize the conversion
195    // that's why we need to specialize this function
196    #[inline]
197    fn from_f32s(from: &[f32], to: &mut [Self]) {
198        to.convert_from_f32_slice(from)
199    }
200}
201
202impl FromNativeSample for Sample {
203    #[inline] fn from_f16(value: f16) -> Self { Self::from(value) }
204    #[inline] fn from_f32(value: f32) -> Self { Self::from(value) }
205    #[inline] fn from_u32(value: u32) -> Self { Self::from(value) }
206}
207
208
209/// Convert any type into one of the supported sample types.
210/// Should be compiled to a no-op where the file contains the predicted sample type
211pub trait IntoNativeSample: Copy + Default + Sync + 'static {
212
213    /// Convert this sample to an f16, trying to represent the same numerical value.
214    fn to_f16(&self) -> f16;
215
216    /// Convert this sample to an f32, trying to represent the same numerical value.
217    fn to_f32(&self) -> f32;
218
219    /// Convert this sample to an u16, trying to represent the same numerical value.
220    fn to_u32(&self) -> u32;
221}
222
223impl IntoNativeSample for f16 {
224    fn to_f16(&self) -> f16 { f16::from_f16(*self) }
225    fn to_f32(&self) -> f32 { f32::from_f16(*self) }
226    fn to_u32(&self) -> u32 { u32::from_f16(*self) }
227}
228
229impl IntoNativeSample for f32 {
230    fn to_f16(&self) -> f16 { f16::from_f32(*self) }
231    fn to_f32(&self) -> f32 { f32::from_f32(*self) }
232    fn to_u32(&self) -> u32 { u32::from_f32(*self) }
233}
234
235impl IntoNativeSample for u32 {
236    fn to_f16(&self) -> f16 { f16::from_u32(*self) }
237    fn to_f32(&self) -> f32 { f32::from_u32(*self) }
238    fn to_u32(&self) -> u32 { u32::from_u32(*self) }
239}
240
241impl IntoNativeSample for Sample {
242    fn to_f16(&self) -> f16 { Sample::to_f16(*self) }
243    fn to_f32(&self) -> f32 { Sample::to_f32(*self) }
244    fn to_u32(&self) -> u32 { Sample::to_u32(*self) }
245}
246
247
248
exr/block/samples.rs

exr/block/
samples.rs
