pixels/
snapshot.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5use std::ops::{Bound, Deref, DerefMut, Range, RangeBounds};
6use std::sync::Arc;
7
8use base::generic_channel::GenericSharedMemory;
9use euclid::default::{Rect, Size2D};
10use image::codecs::jpeg::JpegEncoder;
11use image::codecs::png::PngEncoder;
12use image::codecs::webp::WebPEncoder;
13use image::{ExtendedColorType, GenericImageView, ImageEncoder, ImageError, Rgb};
14use malloc_size_of_derive::MallocSizeOf;
15use serde::{Deserialize, Serialize};
16
17use crate::{EncodedImageType, Multiply, rgba8_get_rect, transform_inplace};
18
19#[derive(Clone, Copy, Debug, Default, Deserialize, Eq, MallocSizeOf, PartialEq, Serialize)]
20pub enum SnapshotPixelFormat {
21    #[default]
22    RGBA,
23    BGRA,
24}
25
26#[derive(Clone, Copy, Debug, Deserialize, Eq, MallocSizeOf, PartialEq, Serialize)]
27pub enum Alpha {
28    Premultiplied,
29    NotPremultiplied,
30    /// This is used for opaque textures for which the presence of alpha in the
31    /// output data format does not matter.
32    DontCare,
33}
34
35impl Alpha {
36    pub const fn from_premultiplied(is_premultiplied: bool) -> Self {
37        if is_premultiplied {
38            Self::Premultiplied
39        } else {
40            Self::NotPremultiplied
41        }
42    }
43
44    pub const fn needs_alpha_multiplication(&self) -> bool {
45        match self {
46            Alpha::Premultiplied => false,
47            Alpha::NotPremultiplied => true,
48            Alpha::DontCare => false,
49        }
50    }
51}
52
53#[derive(Clone, Copy, Debug, Deserialize, Eq, MallocSizeOf, PartialEq, Serialize)]
54pub enum SnapshotAlphaMode {
55    /// Internal data is opaque (alpha is cleared to 1)
56    Opaque,
57    /// Internal data should be treated as opaque (does not mean it actually is)
58    AsOpaque { premultiplied: bool },
59    /// Data is not opaque
60    Transparent { premultiplied: bool },
61}
62
63impl Default for SnapshotAlphaMode {
64    fn default() -> Self {
65        Self::Transparent {
66            premultiplied: true,
67        }
68    }
69}
70
71impl SnapshotAlphaMode {
72    pub const fn alpha(&self) -> Alpha {
73        match self {
74            SnapshotAlphaMode::Opaque => Alpha::DontCare,
75            SnapshotAlphaMode::AsOpaque { premultiplied } => {
76                Alpha::from_premultiplied(*premultiplied)
77            },
78            SnapshotAlphaMode::Transparent { premultiplied } => {
79                Alpha::from_premultiplied(*premultiplied)
80            },
81        }
82    }
83}
84
85/// The data in a [`Snapshot`]. If created via shared memory, this will be
86/// the `SharedMemory` variant, but otherwise it is the `Owned` variant.
87/// any attempt to mutate the [`Snapshot`] will convert it to the `Owned`
88/// variant.
89#[derive(Clone, Debug, MallocSizeOf)]
90pub enum SnapshotData {
91    SharedMemory(
92        #[conditional_malloc_size_of] Arc<GenericSharedMemory>,
93        Range<usize>,
94    ),
95    SharedVec(#[conditional_malloc_size_of] Arc<Vec<u8>>, Range<usize>),
96    Owned(Vec<u8>),
97}
98
99impl SnapshotData {
100    fn to_vec(&self) -> Vec<u8> {
101        match &self {
102            SnapshotData::SharedMemory(data, byte_range) => Vec::from(&data[byte_range.clone()]),
103            SnapshotData::SharedVec(data, byte_range) => Vec::from(&data[byte_range.clone()]),
104            SnapshotData::Owned(data) => data.clone(),
105        }
106    }
107}
108
109impl DerefMut for SnapshotData {
110    fn deref_mut(&mut self) -> &mut Self::Target {
111        match self {
112            SnapshotData::SharedMemory(..) | SnapshotData::SharedVec(..) => {
113                *self = SnapshotData::Owned(self.to_vec());
114                &mut *self
115            },
116            SnapshotData::Owned(items) => items,
117        }
118    }
119}
120
121impl Deref for SnapshotData {
122    type Target = [u8];
123
124    fn deref(&self) -> &Self::Target {
125        match &self {
126            SnapshotData::SharedMemory(data, byte_range) => &data[byte_range.clone()],
127            SnapshotData::SharedVec(data, byte_range) => &data[byte_range.clone()],
128            SnapshotData::Owned(items) => items,
129        }
130    }
131}
132
133/// Represents image bitmap with metadata, usually as snapshot of canvas
134///
135/// This allows us to hold off conversions (BGRA <-> RGBA, (un)premultiply)
136/// to when/if they are actually needed (WebGL/WebGPU can load both BGRA and RGBA).
137///
138/// Inspired by snapshot for concept in WebGPU spec:
139/// <https://gpuweb.github.io/gpuweb/#abstract-opdef-get-a-copy-of-the-image-contents-of-a-context>
140#[derive(Clone, Debug, MallocSizeOf)]
141pub struct Snapshot {
142    size: Size2D<u32>,
143    /// internal data (can be any format it will be converted on use if needed)
144    data: SnapshotData,
145    /// RGBA/BGRA (reflect internal data)
146    format: SnapshotPixelFormat,
147    /// How to treat alpha channel
148    alpha_mode: SnapshotAlphaMode,
149}
150
151impl Snapshot {
152    pub const fn size(&self) -> Size2D<u32> {
153        self.size
154    }
155
156    pub const fn format(&self) -> SnapshotPixelFormat {
157        self.format
158    }
159
160    pub const fn alpha_mode(&self) -> SnapshotAlphaMode {
161        self.alpha_mode
162    }
163
164    pub fn empty() -> Self {
165        Self {
166            size: Size2D::zero(),
167            data: SnapshotData::Owned(vec![]),
168            format: SnapshotPixelFormat::RGBA,
169            alpha_mode: SnapshotAlphaMode::Transparent {
170                premultiplied: true,
171            },
172        }
173    }
174
175    /// Returns snapshot with provided size that is black transparent alpha
176    pub fn cleared(size: Size2D<u32>) -> Self {
177        Self {
178            size,
179            data: SnapshotData::Owned(vec![0; size.area() as usize * 4]),
180            format: SnapshotPixelFormat::RGBA,
181            alpha_mode: SnapshotAlphaMode::Transparent {
182                premultiplied: true,
183            },
184        }
185    }
186
187    pub fn from_vec(
188        size: Size2D<u32>,
189        format: SnapshotPixelFormat,
190        alpha_mode: SnapshotAlphaMode,
191        data: Vec<u8>,
192    ) -> Self {
193        Self {
194            size,
195            data: SnapshotData::Owned(data),
196            format,
197            alpha_mode,
198        }
199    }
200
201    pub fn from_arc_vec(
202        size: Size2D<u32>,
203        format: SnapshotPixelFormat,
204        alpha_mode: SnapshotAlphaMode,
205        data: Arc<Vec<u8>>,
206        byte_range_bounds: impl RangeBounds<usize>,
207    ) -> Self {
208        let range_start = match byte_range_bounds.start_bound() {
209            Bound::Included(bound) => *bound,
210            Bound::Excluded(bound) => *bound + 1,
211            Bound::Unbounded => 0,
212        };
213        let range_end = match byte_range_bounds.end_bound() {
214            Bound::Included(bound) => *bound + 1,
215            Bound::Excluded(bound) => *bound,
216            Bound::Unbounded => data.len(),
217        };
218        Self {
219            size,
220            data: SnapshotData::SharedVec(data, range_start..range_end),
221            format,
222            alpha_mode,
223        }
224    }
225
226    pub fn get_rect(&self, rect: Rect<u32>) -> Self {
227        let data = rgba8_get_rect(self.as_raw_bytes(), self.size(), rect).to_vec();
228        Self::from_vec(rect.size, self.format, self.alpha_mode, data)
229    }
230
231    /// Convert inner data of snapshot to target format and alpha mode.
232    /// If data is already in target format and alpha mode no work will be done.
233    pub fn transform(
234        &mut self,
235        target_alpha_mode: SnapshotAlphaMode,
236        target_format: SnapshotPixelFormat,
237    ) {
238        if self.alpha_mode == target_alpha_mode && target_format == self.format {
239            return;
240        }
241
242        let swap_rb = target_format != self.format;
243        let multiply = match (self.alpha_mode, target_alpha_mode) {
244            (SnapshotAlphaMode::Opaque, _) => Multiply::None,
245            (alpha_mode, SnapshotAlphaMode::Opaque)
246                if alpha_mode.alpha() == Alpha::Premultiplied =>
247            {
248                Multiply::UnMultiply
249            },
250            (_, SnapshotAlphaMode::Opaque) => Multiply::None,
251            (
252                SnapshotAlphaMode::Transparent { premultiplied } |
253                SnapshotAlphaMode::AsOpaque { premultiplied },
254                SnapshotAlphaMode::Transparent {
255                    premultiplied: target_premultiplied,
256                } |
257                SnapshotAlphaMode::AsOpaque {
258                    premultiplied: target_premultiplied,
259                },
260            ) => {
261                if premultiplied == target_premultiplied {
262                    Multiply::None
263                } else if target_premultiplied {
264                    Multiply::PreMultiply
265                } else {
266                    Multiply::UnMultiply
267                }
268            },
269        };
270
271        let clear_alpha = !matches!(self.alpha_mode, SnapshotAlphaMode::Opaque) &&
272            matches!(target_alpha_mode, SnapshotAlphaMode::Opaque);
273
274        if matches!(multiply, Multiply::None) && !swap_rb && !clear_alpha {
275            return;
276        }
277
278        transform_inplace(self.data.deref_mut(), multiply, swap_rb, clear_alpha);
279        self.alpha_mode = target_alpha_mode;
280        self.format = target_format;
281    }
282
283    pub fn as_raw_bytes(&self) -> &[u8] {
284        &self.data
285    }
286
287    pub fn as_raw_bytes_mut(&mut self) -> &mut [u8] {
288        &mut self.data
289    }
290
291    pub fn to_shared(&self) -> SharedSnapshot {
292        let (data, byte_range) = match &self.data {
293            SnapshotData::SharedMemory(data, byte_range) => (data.clone(), byte_range.clone()),
294            SnapshotData::SharedVec(data, byte_range) => (
295                Arc::new(GenericSharedMemory::from_bytes(data)),
296                byte_range.clone(),
297            ),
298            SnapshotData::Owned(data) => (
299                Arc::new(GenericSharedMemory::from_bytes(data)),
300                0..data.len(),
301            ),
302        };
303        SharedSnapshot {
304            size: self.size,
305            data,
306            byte_range,
307            format: self.format,
308            alpha_mode: self.alpha_mode,
309        }
310    }
311
312    pub fn encode_for_mime_type<W: std::io::Write>(
313        &mut self,
314        image_type: &EncodedImageType,
315        quality: Option<f64>,
316        encoder: &mut W,
317    ) -> Result<(), ImageError> {
318        let width = self.size.width;
319        let height = self.size.height;
320        let alpha_mode = match image_type {
321            EncodedImageType::Jpeg => SnapshotAlphaMode::AsOpaque {
322                premultiplied: true,
323            },
324            _ => SnapshotAlphaMode::Transparent {
325                premultiplied: false,
326            },
327        };
328
329        self.transform(alpha_mode, SnapshotPixelFormat::RGBA);
330        let data = &self.data;
331
332        match image_type {
333            EncodedImageType::Png => {
334                // FIXME(nox): https://github.com/image-rs/image-png/issues/86
335                // FIXME(nox): https://github.com/image-rs/image-png/issues/87
336                PngEncoder::new(encoder).write_image(data, width, height, ExtendedColorType::Rgba8)
337            },
338            EncodedImageType::Jpeg => {
339                let mut jpeg_encoder = if let Some(quality) = quality {
340                    // The specification allows quality to be in [0.0..1.0] but the JPEG encoder
341                    // expects it to be in [1..100]
342                    if (0.0..=1.0).contains(&quality) {
343                        JpegEncoder::new_with_quality(
344                            encoder,
345                            (quality * 100.0).round().clamp(1.0, 100.0) as u8,
346                        )
347                    } else {
348                        JpegEncoder::new(encoder)
349                    }
350                } else {
351                    JpegEncoder::new(encoder)
352                };
353
354                // JPEG doesn't support transparency, so simply calling jpeg_encoder.write_image fails here.
355                // Instead we have to create a struct to translate from rgba to rgb.
356                struct RgbaDataForJpegEncoder<'a> {
357                    width: u32,
358                    height: u32,
359                    data: &'a [u8],
360                }
361
362                impl<'a> GenericImageView for RgbaDataForJpegEncoder<'a> {
363                    type Pixel = Rgb<u8>;
364
365                    fn dimensions(&self) -> (u32, u32) {
366                        (self.width, self.height)
367                    }
368
369                    fn get_pixel(&self, x: u32, y: u32) -> Self::Pixel {
370                        let offset = (self.width * y + x) as usize * 4;
371                        Rgb([
372                            self.data[offset],
373                            self.data[offset + 1],
374                            self.data[offset + 2],
375                        ])
376                    }
377                }
378
379                let image = RgbaDataForJpegEncoder {
380                    width,
381                    height,
382                    data,
383                };
384
385                jpeg_encoder.encode_image(&image)
386            },
387            EncodedImageType::Webp => {
388                // No quality support because of https://github.com/image-rs/image/issues/1984
389                WebPEncoder::new_lossless(encoder).write_image(
390                    data,
391                    width,
392                    height,
393                    ExtendedColorType::Rgba8,
394                )
395            },
396        }
397    }
398}
399
400impl From<Snapshot> for Vec<u8> {
401    fn from(value: Snapshot) -> Self {
402        match value.data {
403            SnapshotData::SharedMemory(..) => Vec::from(value.as_raw_bytes()),
404            SnapshotData::SharedVec(..) => Vec::from(value.as_raw_bytes()),
405            SnapshotData::Owned(data) => data,
406        }
407    }
408}
409
410/// A version of [`Snapshot`] that can be sent across IPC channels.
411#[derive(Clone, Debug, Deserialize, MallocSizeOf, Serialize)]
412pub struct SharedSnapshot {
413    /// The physical size of this [`SharedSnapshot`].
414    size: Size2D<u32>,
415    /// The shared data of this [`SharedSnapshot`].
416    #[conditional_malloc_size_of]
417    data: Arc<GenericSharedMemory>,
418    /// The byte range of the data within the shared memory segment. This is used to
419    /// send individual image frames of animated images.
420    byte_range: Range<usize>,
421    /// The [`SnapshotPixelFormat`] of this [`SharedSnapshot`]
422    format: SnapshotPixelFormat,
423    /// The [`SnapshotAlphaMode`] of this [`SharedSnapshot`].
424    alpha_mode: SnapshotAlphaMode,
425}
426
427impl SharedSnapshot {
428    pub fn to_owned(&self) -> Snapshot {
429        Snapshot {
430            size: self.size,
431            data: SnapshotData::SharedMemory(self.data.clone(), self.byte_range.clone()),
432            format: self.format,
433            alpha_mode: self.alpha_mode,
434        }
435    }
436
437    /// Returns snapshot with provided size that is black transparent alpha
438    pub fn cleared(size: Size2D<u32>) -> Self {
439        let length_in_bytes = size.area() as usize * 4;
440        Self {
441            size,
442            data: Arc::new(GenericSharedMemory::from_byte(0, length_in_bytes)),
443            byte_range: 0..length_in_bytes,
444            format: SnapshotPixelFormat::RGBA,
445            alpha_mode: SnapshotAlphaMode::Transparent {
446                premultiplied: true,
447            },
448        }
449    }
450
451    pub const fn size(&self) -> Size2D<u32> {
452        self.size
453    }
454
455    pub const fn format(&self) -> SnapshotPixelFormat {
456        self.format
457    }
458
459    pub const fn alpha_mode(&self) -> SnapshotAlphaMode {
460        self.alpha_mode
461    }
462
463    pub fn data(&self) -> &[u8] {
464        &(&self.data)[self.byte_range.clone()]
465    }
466
467    pub fn shared_memory(&self) -> GenericSharedMemory {
468        (*self.data).clone()
469    }
470}
pixels/snapshot.rs

pixels/
snapshot.rs
