exr/image/read/
specific_channels.rs

1//! How to read arbitrary but specific selection of arbitrary channels.
2//! This is not a zero-cost abstraction.
3
4use crate::image::recursive::*;
5use crate::block::samples::*;
6use crate::image::*;
7use crate::math::*;
8use crate::meta::header::*;
9use crate::error::*;
10use crate::block::UncompressedBlock;
11use crate::image::read::layers::{ChannelsReader, ReadChannels};
12use crate::block::chunk::TileCoordinates;
13
14use std::marker::PhantomData;
15use crate::io::Read;
16
17
18/// Can be attached one more channel reader.
19/// Call `required` or `optional` on this object to declare another channel to be read from the file.
20/// Call `collect_pixels` at last to define how the previously declared pixels should be stored.
21pub trait ReadSpecificChannel: Sized + CheckDuplicates {
22
23    /// A separate internal reader for the pixels. Will be of type `Recursive<_, SampleReader<_>>`,
24    /// depending on the pixels of the specific channel combination.
25    type RecursivePixelReader: RecursivePixelReader;
26
27    /// Create a separate internal reader for the pixels of the specific channel combination.
28    fn create_recursive_reader(&self, channels: &ChannelList) -> Result<Self::RecursivePixelReader>;
29
30    /// Plan to read an additional channel from the image, with the specified name.
31    /// If the channel cannot be found in the image when the image is read, the image will not be loaded.
32    /// The generic parameter can usually be inferred from the closure in `collect_pixels`.
33    fn required<Sample>(self, channel_name: impl Into<Text>) -> ReadRequiredChannel<Self, Sample> {
34        let channel_name = channel_name.into();
35        assert!(self.already_contains(&channel_name).not(), "a channel with the name `{}` is already defined", channel_name);
36        ReadRequiredChannel { channel_name, previous_channels: self, px: Default::default() }
37    }
38
39    /// Plan to read an additional channel from the image, with the specified name.
40    /// If the file does not contain this channel, the specified default sample will be returned instead.
41    /// You can check whether the channel has been loaded by
42    /// checking the presence of the optional channel description before instantiating your own image.
43    /// The generic parameter can usually be inferred from the closure in `collect_pixels`.
44    fn optional<Sample>(self, channel_name: impl Into<Text>, default_sample: Sample)
45        -> ReadOptionalChannel<Self, Sample>
46    {
47        let channel_name = channel_name.into();
48        assert!(self.already_contains(&channel_name).not(), "a channel with the name `{}` is already defined", channel_name);
49        ReadOptionalChannel { channel_name, previous_channels: self, default_sample }
50    }
51
52    /// Using two closures, define how to store the pixels.
53    /// The first closure creates an image, and the second closure inserts a single pixel.
54    /// The type of the pixel can be defined by the second closure;
55    /// it must be a tuple containing `f16`, `f32`, `u32` or `Sample` values.
56    /// See the examples for more information.
57    fn collect_pixels<Pixel, PixelStorage, CreatePixels, SetPixel>(
58        self, create_pixels: CreatePixels, set_pixel: SetPixel
59    ) -> CollectPixels<Self, Pixel, PixelStorage, CreatePixels, SetPixel>
60        where
61            <Self::RecursivePixelReader as RecursivePixelReader>::RecursivePixel: IntoTuple<Pixel>,
62            <Self::RecursivePixelReader as RecursivePixelReader>::RecursiveChannelDescriptions: IntoNonRecursive,
63            CreatePixels: Fn(
64                Vec2<usize>,
65                &<<Self::RecursivePixelReader as RecursivePixelReader>::RecursiveChannelDescriptions as IntoNonRecursive>::NonRecursive
66            ) -> PixelStorage,
67            SetPixel: Fn(&mut PixelStorage, Vec2<usize>, Pixel),
68    {
69        CollectPixels { read_channels: self, set_pixel, create_pixels, px: Default::default() }
70    }
71}
72
73/// A reader containing sub-readers for reading the pixel content of an image.
74pub trait RecursivePixelReader {
75
76    /// The channel descriptions from the image.
77    /// Will be converted to a tuple before being stored in `SpecificChannels<_, ChannelDescriptions>`.
78    type RecursiveChannelDescriptions;
79
80    /// Returns the channel descriptions based on the channels in the file.
81    fn get_descriptions(&self) -> Self::RecursiveChannelDescriptions;
82
83    /// The pixel type. Will be converted to a tuple at the end of the process.
84    type RecursivePixel: Copy + Default + 'static;
85
86    /// Read the line of pixels.
87    fn read_pixels<'s, FullPixel>(
88        &self, bytes: &'s[u8], pixels: &mut [FullPixel],
89        get_pixel: impl Fn(&mut FullPixel) -> &mut Self::RecursivePixel
90    );
91}
92
93// does not use the generic `Recursive` struct to reduce the number of angle brackets in the public api
94/// Used to read another specific channel from an image.
95/// Contains the previous `ReadChannels` objects.
96#[derive(Clone, Debug)]
97pub struct ReadOptionalChannel<ReadChannels, Sample> {
98    previous_channels: ReadChannels,
99    channel_name: Text,
100    default_sample: Sample,
101}
102
103// does not use the generic `Recursive` struct to reduce the number of angle brackets in the public api
104/// Used to read another specific channel from an image.
105/// Contains the previous `ReadChannels` objects.
106#[derive(Clone, Debug)]
107pub struct ReadRequiredChannel<ReadChannels, Sample> {
108    previous_channels: ReadChannels,
109    channel_name: Text,
110    px: PhantomData<Sample>,
111}
112
113/// Specifies how to collect all the specified channels into a number of individual pixels.
114#[derive(Copy, Clone, Debug)]
115pub struct CollectPixels<ReadChannels, Pixel, PixelStorage, CreatePixels, SetPixel> {
116    read_channels: ReadChannels,
117    create_pixels: CreatePixels,
118    set_pixel: SetPixel,
119    px: PhantomData<(Pixel, PixelStorage)>,
120}
121
122impl<Inner: CheckDuplicates, Sample> CheckDuplicates for ReadRequiredChannel<Inner, Sample> {
123    fn already_contains(&self, name: &Text) -> bool {
124        &self.channel_name == name || self.previous_channels.already_contains(name)
125    }
126}
127
128impl<Inner: CheckDuplicates, Sample> CheckDuplicates for ReadOptionalChannel<Inner, Sample> {
129    fn already_contains(&self, name: &Text) -> bool {
130        &self.channel_name == name || self.previous_channels.already_contains(name)
131    }
132}
133
134impl<'s, InnerChannels, Pixel, PixelStorage, CreatePixels, SetPixel: 's>
135ReadChannels<'s> for CollectPixels<InnerChannels, Pixel, PixelStorage, CreatePixels, SetPixel>
136    where
137        InnerChannels: ReadSpecificChannel,
138        <InnerChannels::RecursivePixelReader as RecursivePixelReader>::RecursivePixel: IntoTuple<Pixel>,
139        <InnerChannels::RecursivePixelReader as RecursivePixelReader>::RecursiveChannelDescriptions: IntoNonRecursive,
140        CreatePixels: Fn(Vec2<usize>, &<<InnerChannels::RecursivePixelReader as RecursivePixelReader>::RecursiveChannelDescriptions as IntoNonRecursive>::NonRecursive) -> PixelStorage,
141        SetPixel: Fn(&mut PixelStorage, Vec2<usize>, Pixel),
142{
143    type Reader = SpecificChannelsReader<
144        PixelStorage, &'s SetPixel,
145        InnerChannels::RecursivePixelReader,
146        Pixel,
147    >;
148
149    fn create_channels_reader(&'s self, header: &Header) -> Result<Self::Reader> {
150        if header.deep { return Err(Error::invalid("`SpecificChannels` does not support deep data yet")) }
151
152        let pixel_reader = self.read_channels.create_recursive_reader(&header.channels)?;
153        let channel_descriptions = pixel_reader.get_descriptions().into_non_recursive();// TODO not call this twice
154
155        let create = &self.create_pixels;
156        let pixel_storage = create(header.layer_size, &channel_descriptions);
157
158        Ok(SpecificChannelsReader {
159            set_pixel: &self.set_pixel,
160            pixel_storage,
161            pixel_reader,
162            px: Default::default()
163        })
164    }
165}
166
167/// The reader that holds the temporary data that is required to read some specified channels.
168#[derive(Copy, Clone, Debug)]
169pub struct SpecificChannelsReader<PixelStorage, SetPixel, PixelReader, Pixel> {
170    set_pixel: SetPixel,
171    pixel_storage: PixelStorage,
172    pixel_reader: PixelReader,
173    px: PhantomData<Pixel>
174}
175
176impl<PixelStorage, SetPixel, PxReader, Pixel>
177ChannelsReader for SpecificChannelsReader<PixelStorage, SetPixel, PxReader, Pixel>
178    where PxReader: RecursivePixelReader,
179          PxReader::RecursivePixel: IntoTuple<Pixel>,
180          PxReader::RecursiveChannelDescriptions: IntoNonRecursive,
181          SetPixel: Fn(&mut PixelStorage, Vec2<usize>, Pixel),
182{
183    type Channels = SpecificChannels<PixelStorage, <PxReader::RecursiveChannelDescriptions as IntoNonRecursive>::NonRecursive>;
184
185    fn filter_block(&self, tile: TileCoordinates) -> bool { tile.is_largest_resolution_level() } // TODO all levels
186
187    fn read_block(&mut self, header: &Header, block: UncompressedBlock) -> UnitResult {
188        let mut pixels = vec![PxReader::RecursivePixel::default(); block.index.pixel_size.width()]; // TODO allocate once in self
189
190        let byte_lines = block.data.chunks_exact(header.channels.bytes_per_pixel * block.index.pixel_size.width());
191        debug_assert_eq!(byte_lines.len(), block.index.pixel_size.height(), "invalid block lines split");
192
193        for (y_offset, line_bytes) in byte_lines.enumerate() { // TODO sampling
194            // this two-step copy method should be very cache friendly in theory, and also reduce sample_type lookup count
195            self.pixel_reader.read_pixels(line_bytes, &mut pixels, |px| px);
196
197            for (x_offset, pixel) in pixels.iter().enumerate() {
198                let set_pixel = &self.set_pixel;
199                set_pixel(&mut self.pixel_storage, block.index.pixel_position + Vec2(x_offset, y_offset), pixel.into_tuple());
200            }
201        }
202
203        Ok(())
204    }
205
206    fn into_channels(self) -> Self::Channels {
207        SpecificChannels { channels: self.pixel_reader.get_descriptions().into_non_recursive(), pixels: self.pixel_storage }
208    }
209}
210
211
212/// Read zero channels from an image. Call `with_named_channel` on this object
213/// to read as many channels as desired.
214pub type ReadZeroChannels = NoneMore;
215
216impl ReadSpecificChannel for NoneMore {
217    type RecursivePixelReader = NoneMore;
218    fn create_recursive_reader(&self, _: &ChannelList) -> Result<Self::RecursivePixelReader> { Ok(NoneMore) }
219}
220
221impl<DefaultSample, ReadChannels> ReadSpecificChannel for ReadOptionalChannel<ReadChannels, DefaultSample>
222    where ReadChannels: ReadSpecificChannel, DefaultSample: FromNativeSample + 'static,
223{
224    type RecursivePixelReader = Recursive<ReadChannels::RecursivePixelReader, OptionalSampleReader<DefaultSample>>;
225
226    fn create_recursive_reader(&self, channels: &ChannelList) -> Result<Self::RecursivePixelReader> {
227        debug_assert!(self.previous_channels.already_contains(&self.channel_name).not(), "duplicate channel name: {}", self.channel_name);
228
229        let inner_samples_reader = self.previous_channels.create_recursive_reader(channels)?;
230        let reader = channels.channels_with_byte_offset()
231            .find(|(_, channel)| channel.name == self.channel_name)
232            .map(|(channel_byte_offset, channel)| SampleReader {
233                channel_byte_offset, channel: channel.clone(),
234                px: Default::default()
235            });
236
237        Ok(Recursive::new(inner_samples_reader, OptionalSampleReader {
238            reader, default_sample: self.default_sample,
239        }))
240    }
241}
242
243impl<Sample, ReadChannels> ReadSpecificChannel for ReadRequiredChannel<ReadChannels, Sample>
244    where ReadChannels: ReadSpecificChannel, Sample: FromNativeSample + 'static
245{
246    type RecursivePixelReader = Recursive<ReadChannels::RecursivePixelReader, SampleReader<Sample>>;
247
248    fn create_recursive_reader(&self, channels: &ChannelList) -> Result<Self::RecursivePixelReader> {
249        let previous_samples_reader = self.previous_channels.create_recursive_reader(channels)?;
250        let (channel_byte_offset, channel) = channels.channels_with_byte_offset()
251                .find(|(_, channel)| channel.name == self.channel_name)
252                .ok_or_else(|| Error::invalid(format!(
253                    "layer does not contain all of your specified channels (`{}` is missing)",
254                    self.channel_name
255                )))?;
256
257        Ok(Recursive::new(previous_samples_reader, SampleReader { channel_byte_offset, channel: channel.clone(), px: Default::default() }))
258    }
259}
260
261/// Reader for a single channel. Generic over the concrete sample type (f16, f32, u32).
262#[derive(Clone, Debug)]
263pub struct SampleReader<Sample> {
264
265    /// to be multiplied with line width!
266    channel_byte_offset: usize,
267
268    channel: ChannelDescription,
269    px: PhantomData<Sample>
270}
271
272/// Reader for a single channel. Generic over the concrete sample type (f16, f32, u32).
273/// Can also skip reading a channel if it could not be found in the image.
274#[derive(Clone, Debug)]
275pub struct OptionalSampleReader<DefaultSample> {
276    reader: Option<SampleReader<DefaultSample>>,
277    default_sample: DefaultSample,
278}
279
280impl<Sample: FromNativeSample> SampleReader<Sample> {
281    fn read_own_samples<'s, FullPixel>(
282        &self, bytes: &'s[u8], pixels: &mut [FullPixel],
283        get_sample: impl Fn(&mut FullPixel) -> &mut Sample
284    ){
285        let start_index = pixels.len() * self.channel_byte_offset;
286        let byte_count = pixels.len() * self.channel.sample_type.bytes_per_sample();
287        let mut own_bytes_reader = &mut &bytes[start_index .. start_index + byte_count]; // TODO check block size somewhere
288        let mut samples_out = pixels.iter_mut().map(|pixel| get_sample(pixel));
289
290        // match the type once for the whole line, not on every single sample
291        match self.channel.sample_type {
292            SampleType::F16 => read_and_convert_all_samples_batched(
293                &mut own_bytes_reader, &mut samples_out,
294                Sample::from_f16s
295            ),
296
297            SampleType::F32 => read_and_convert_all_samples_batched(
298                &mut own_bytes_reader, &mut samples_out,
299                Sample::from_f32s
300            ),
301
302            SampleType::U32 => read_and_convert_all_samples_batched(
303                &mut own_bytes_reader, &mut samples_out,
304                Sample::from_u32s
305            ),
306        }
307
308        debug_assert!(samples_out.next().is_none(), "not all samples have been converted");
309        debug_assert!(own_bytes_reader.is_empty(), "bytes left after reading all samples");
310    }
311}
312
313
314/// Does the same as `convert_batch(in_bytes.chunks().map(From::from_bytes))`, but vectorized.
315/// Reads the samples for one line, using the sample type specified in the file,
316/// and then converts those to the desired sample types.
317/// Uses batches to allow vectorization, converting multiple values with one instruction.
318/// Does not convert endianness.
319fn read_and_convert_all_samples_batched<'t, From, To>(
320    mut in_bytes: impl Read,
321    out_samples: &mut impl ExactSizeIterator<Item=&'t mut To>,
322    convert_batch: fn(&[From], &mut [To])
323) where From: Data + Default + Copy, To: 't + Default + Copy
324{
325    // this is not a global! why is this warning triggered?
326    #[allow(non_upper_case_globals)]
327    const batch_size: usize = 16;
328
329    let total_sample_count = out_samples.len();
330    let batch_count = total_sample_count / batch_size;
331    let remaining_samples_count = total_sample_count % batch_size;
332
333    let len_error_msg = "sample count was miscalculated";
334    let byte_error_msg = "error when reading from in-memory slice";
335
336    // write samples from a given slice to the output iterator. should be inlined.
337    let output_n_samples = &mut move |samples: &[To]| {
338        for converted_sample in samples {
339            *out_samples.next().expect(len_error_msg) = *converted_sample;
340        }
341    };
342
343    // read samples from the byte source into a given slice. should be inlined.
344    // todo: use #[inline] when available
345    // error[E0658]: attributes on expressions are experimental,
346    // see issue #15701 <https://github.com/rust-lang/rust/issues/15701> for more information
347    let read_n_samples = &mut move |samples: &mut [From]| {
348        Data::read_slice_ne(&mut in_bytes, samples).expect(byte_error_msg);
349    };
350
351    // temporary arrays with fixed size, operations should be vectorized within these arrays
352    let mut source_samples_batch: [From; batch_size] = Default::default();
353    let mut desired_samples_batch: [To; batch_size] = Default::default();
354
355    // first convert all whole batches, size statically known to be 16 element arrays
356    for _ in 0 .. batch_count {
357        read_n_samples(&mut source_samples_batch);
358        convert_batch(source_samples_batch.as_slice(), desired_samples_batch.as_mut_slice());
359        output_n_samples(&desired_samples_batch);
360    }
361
362    // then convert a partial remaining batch, size known only at runtime
363    if remaining_samples_count != 0 {
364        let source_samples_batch = &mut source_samples_batch[..remaining_samples_count];
365        let desired_samples_batch = &mut desired_samples_batch[..remaining_samples_count];
366
367        read_n_samples(source_samples_batch);
368        convert_batch(source_samples_batch, desired_samples_batch);
369        output_n_samples(desired_samples_batch);
370    }
371}
372
373#[cfg(test)]
374mod test {
375    use super::*;
376
377    #[test]
378    fn equals_naive_f32(){
379        for total_array_size in [3, 7, 30, 41, 120, 10_423] {
380            let input_f32s = (0..total_array_size).map(|_| rand::random::<f32>()).collect::<Vec<f32>>();
381            let in_f32s_bytes = input_f32s.iter().cloned().flat_map(f32::to_ne_bytes).collect::<Vec<u8>>();
382
383            let mut out_f16_samples_batched = vec![
384                f16::from_f32(rand::random::<f32>());
385                total_array_size
386            ];
387
388            read_and_convert_all_samples_batched(
389                &mut in_f32s_bytes.as_slice(),
390                &mut out_f16_samples_batched.iter_mut(),
391                f16::from_f32s
392            );
393
394            let out_f16_samples_naive = input_f32s.iter()
395                .cloned().map(f16::from_f32);
396
397            assert!(out_f16_samples_naive.eq(out_f16_samples_batched));
398        }
399    }
400}
401
402
403impl RecursivePixelReader for NoneMore {
404    type RecursiveChannelDescriptions = NoneMore;
405    fn get_descriptions(&self) -> Self::RecursiveChannelDescriptions { NoneMore }
406
407    type RecursivePixel = NoneMore;
408
409    fn read_pixels<'s, FullPixel>(
410        &self, _: &'s[u8], _: &mut [FullPixel],
411        _: impl Fn(&mut FullPixel) -> &mut NoneMore
412    ){}
413}
414
415impl<Sample, InnerReader: RecursivePixelReader>
416    RecursivePixelReader
417    for Recursive<InnerReader, SampleReader<Sample>>
418    where Sample: FromNativeSample + 'static
419{
420    type RecursiveChannelDescriptions = Recursive<InnerReader::RecursiveChannelDescriptions, ChannelDescription>;
421    fn get_descriptions(&self) -> Self::RecursiveChannelDescriptions { Recursive::new(self.inner.get_descriptions(), self.value.channel.clone()) }
422
423    type RecursivePixel = Recursive<InnerReader::RecursivePixel, Sample>;
424
425    fn read_pixels<'s, FullPixel>(
426        &self, bytes: &'s[u8], pixels: &mut [FullPixel],
427        get_pixel: impl Fn(&mut FullPixel) -> &mut Self::RecursivePixel
428    ) {
429        self.value.read_own_samples(bytes, pixels, |px| &mut get_pixel(px).value);
430        self.inner.read_pixels(bytes, pixels, |px| &mut get_pixel(px).inner);
431    }
432}
433
434impl<Sample, InnerReader: RecursivePixelReader>
435RecursivePixelReader
436for Recursive<InnerReader, OptionalSampleReader<Sample>>
437    where Sample: FromNativeSample + 'static
438{
439    type RecursiveChannelDescriptions = Recursive<InnerReader::RecursiveChannelDescriptions, Option<ChannelDescription>>;
440    fn get_descriptions(&self) -> Self::RecursiveChannelDescriptions { Recursive::new(
441        self.inner.get_descriptions(), self.value.reader.as_ref().map(|reader| reader.channel.clone())
442    ) }
443
444    type RecursivePixel = Recursive<InnerReader::RecursivePixel, Sample>;
445
446    fn read_pixels<'s, FullPixel>(
447        &self, bytes: &'s[u8], pixels: &mut [FullPixel],
448        get_pixel: impl Fn(&mut FullPixel) -> &mut Self::RecursivePixel
449    ) {
450        if let Some(reader) = &self.value.reader {
451            reader.read_own_samples(bytes, pixels, |px| &mut get_pixel(px).value);
452        }
453        else {
454            // if this channel is optional and was not found in the file, fill the default sample
455            for pixel in pixels.iter_mut() {
456                get_pixel(pixel).value = self.value.default_sample;
457            }
458        }
459
460        self.inner.read_pixels(bytes, pixels, |px| &mut get_pixel(px).inner);
461    }
462}
463
464
exr/image/read/specific_channels.rs

exr/image/read/
specific_channels.rs
