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+use crate::error::{Error, Result, UnsupportedFeature};
+use crate::huffman::{fill_default_mjpeg_tables, HuffmanDecoder, HuffmanTable};
+use crate::marker::Marker;
+use crate::parser::{
+ parse_app, parse_com, parse_dht, parse_dqt, parse_dri, parse_sof, parse_sos,
+ AdobeColorTransform, AppData, CodingProcess, Component, Dimensions, EntropyCoding, FrameInfo,
+ IccChunk, ScanInfo,
+};
+use crate::read_u8;
+use crate::upsampler::Upsampler;
+use crate::worker::{compute_image_parallel, PreferWorkerKind, RowData, Worker, WorkerScope};
+use alloc::borrow::ToOwned;
+use alloc::sync::Arc;
+use alloc::vec::Vec;
+use alloc::{format, vec};
+use core::cmp;
+use core::mem;
+use core::ops::Range;
+use std::convert::TryInto;
+use std::io::Read;
+
+pub const MAX_COMPONENTS: usize = 4;
+
+mod lossless;
+use self::lossless::compute_image_lossless;
+
+#[cfg_attr(rustfmt, rustfmt_skip)]
+static UNZIGZAG: [u8; 64] = [
+ 0, 1, 8, 16, 9, 2, 3, 10,
+ 17, 24, 32, 25, 18, 11, 4, 5,
+ 12, 19, 26, 33, 40, 48, 41, 34,
+ 27, 20, 13, 6, 7, 14, 21, 28,
+ 35, 42, 49, 56, 57, 50, 43, 36,
+ 29, 22, 15, 23, 30, 37, 44, 51,
+ 58, 59, 52, 45, 38, 31, 39, 46,
+ 53, 60, 61, 54, 47, 55, 62, 63,
+];
+
+/// An enumeration over combinations of color spaces and bit depths a pixel can have.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum PixelFormat {
+ /// Luminance (grayscale), 8 bits
+ L8,
+ /// Luminance (grayscale), 16 bits
+ L16,
+ /// RGB, 8 bits per channel
+ RGB24,
+ /// CMYK, 8 bits per channel
+ CMYK32,
+}
+
+impl PixelFormat {
+ /// Determine the size in bytes of each pixel in this format
+ pub fn pixel_bytes(&self) -> usize {
+ match self {
+ PixelFormat::L8 => 1,
+ PixelFormat::L16 => 2,
+ PixelFormat::RGB24 => 3,
+ PixelFormat::CMYK32 => 4,
+ }
+ }
+}
+
+/// Represents metadata of an image.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct ImageInfo {
+ /// The width of the image, in pixels.
+ pub width: u16,
+ /// The height of the image, in pixels.
+ pub height: u16,
+ /// The pixel format of the image.
+ pub pixel_format: PixelFormat,
+ /// The coding process of the image.
+ pub coding_process: CodingProcess,
+}
+
+/// Describes the colour transform to apply before binary data is returned
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+#[non_exhaustive]
+pub enum ColorTransform {
+ /// No transform should be applied and the data is returned as-is.
+ None,
+ /// Unknown colour transformation
+ Unknown,
+ /// Grayscale transform should be applied (expects 1 channel)
+ Grayscale,
+ /// RGB transform should be applied.
+ RGB,
+ /// YCbCr transform should be applied.
+ YCbCr,
+ /// CMYK transform should be applied.
+ CMYK,
+ /// YCCK transform should be applied.
+ YCCK,
+ /// big gamut Y/Cb/Cr, bg-sYCC
+ JcsBgYcc,
+ /// big gamut red/green/blue, bg-sRGB
+ JcsBgRgb,
+}
+
+/// JPEG decoder
+pub struct Decoder<R> {
+ reader: R,
+
+ frame: Option<FrameInfo>,
+ dc_huffman_tables: Vec<Option<HuffmanTable>>,
+ ac_huffman_tables: Vec<Option<HuffmanTable>>,
+ quantization_tables: [Option<Arc<[u16; 64]>>; 4],
+
+ restart_interval: u16,
+
+ adobe_color_transform: Option<AdobeColorTransform>,
+ color_transform: Option<ColorTransform>,
+
+ is_jfif: bool,
+ is_mjpeg: bool,
+
+ icc_markers: Vec<IccChunk>,
+
+ exif_data: Option<Vec<u8>>,
+
+ // Used for progressive JPEGs.
+ coefficients: Vec<Vec<i16>>,
+ // Bitmask of which coefficients has been completely decoded.
+ coefficients_finished: [u64; MAX_COMPONENTS],
+
+ // Maximum allowed size of decoded image buffer
+ decoding_buffer_size_limit: usize,
+}
+
+impl<R: Read> Decoder<R> {
+ /// Creates a new `Decoder` using the reader `reader`.
+ pub fn new(reader: R) -> Decoder<R> {
+ Decoder {
+ reader,
+ frame: None,
+ dc_huffman_tables: vec![None, None, None, None],
+ ac_huffman_tables: vec![None, None, None, None],
+ quantization_tables: [None, None, None, None],
+ restart_interval: 0,
+ adobe_color_transform: None,
+ color_transform: None,
+ is_jfif: false,
+ is_mjpeg: false,
+ icc_markers: Vec::new(),
+ exif_data: None,
+ coefficients: Vec::new(),
+ coefficients_finished: [0; MAX_COMPONENTS],
+ decoding_buffer_size_limit: usize::MAX,
+ }
+ }
+
+ /// Colour transform to use when decoding the image. App segments relating to colour transforms
+ /// will be ignored.
+ pub fn set_color_transform(&mut self, transform: ColorTransform) {
+ self.color_transform = Some(transform);
+ }
+
+ /// Set maximum buffer size allowed for decoded images
+ pub fn set_max_decoding_buffer_size(&mut self, max: usize) {
+ self.decoding_buffer_size_limit = max;
+ }
+
+ /// Returns metadata about the image.
+ ///
+ /// The returned value will be `None` until a call to either `read_info` or `decode` has
+ /// returned `Ok`.
+ pub fn info(&self) -> Option<ImageInfo> {
+ match self.frame {
+ Some(ref frame) => {
+ let pixel_format = match frame.components.len() {
+ 1 => match frame.precision {
+ 8 => PixelFormat::L8,
+ 16 => PixelFormat::L16,
+ _ => panic!(),
+ },
+ 3 => PixelFormat::RGB24,
+ 4 => PixelFormat::CMYK32,
+ _ => panic!(),
+ };
+
+ Some(ImageInfo {
+ width: frame.output_size.width,
+ height: frame.output_size.height,
+ pixel_format,
+ coding_process: frame.coding_process,
+ })
+ }
+ None => None,
+ }
+ }
+
+ /// Returns raw exif data, starting at the TIFF header, if the image contains any.
+ ///
+ /// The returned value will be `None` until a call to `decode` has returned `Ok`.
+ pub fn exif_data(&self) -> Option<&[u8]> {
+ self.exif_data.as_deref()
+ }
+
+ /// Returns the embeded icc profile if the image contains one.
+ pub fn icc_profile(&self) -> Option<Vec<u8>> {
+ let mut marker_present: [Option<&IccChunk>; 256] = [None; 256];
+ let num_markers = self.icc_markers.len();
+ if num_markers == 0 || num_markers >= 255 {
+ return None;
+ }
+ // check the validity of the markers
+ for chunk in &self.icc_markers {
+ if usize::from(chunk.num_markers) != num_markers {
+ // all the lengths must match
+ return None;
+ }
+ if chunk.seq_no == 0 {
+ return None;
+ }
+ if marker_present[usize::from(chunk.seq_no)].is_some() {
+ // duplicate seq_no
+ return None;
+ } else {
+ marker_present[usize::from(chunk.seq_no)] = Some(chunk);
+ }
+ }
+
+ // assemble them together by seq_no failing if any are missing
+ let mut data = Vec::new();
+ // seq_no's start at 1
+ for &chunk in marker_present.get(1..=num_markers)? {
+ data.extend_from_slice(&chunk?.data);
+ }
+ Some(data)
+ }
+
+ /// Heuristic to avoid starting thread, synchronization if we expect a small amount of
+ /// parallelism to be utilized.
+ fn select_worker(frame: &FrameInfo, worker_preference: PreferWorkerKind) -> PreferWorkerKind {
+ const PARALLELISM_THRESHOLD: u64 = 128 * 128;
+
+ match worker_preference {
+ PreferWorkerKind::Immediate => PreferWorkerKind::Immediate,
+ PreferWorkerKind::Multithreaded => {
+ let width: u64 = frame.output_size.width.into();
+ let height: u64 = frame.output_size.width.into();
+ if width * height > PARALLELISM_THRESHOLD {
+ PreferWorkerKind::Multithreaded
+ } else {
+ PreferWorkerKind::Immediate
+ }
+ }
+ }
+ }
+
+ /// Tries to read metadata from the image without decoding it.
+ ///
+ /// If successful, the metadata can be obtained using the `info` method.
+ pub fn read_info(&mut self) -> Result<()> {
+ WorkerScope::with(|worker| self.decode_internal(true, worker)).map(|_| ())
+ }
+
+ /// Configure the decoder to scale the image during decoding.
+ ///
+ /// This efficiently scales the image by the smallest supported scale
+ /// factor that produces an image larger than or equal to the requested
+ /// size in at least one axis. The currently implemented scale factors
+ /// are 1/8, 1/4, 1/2 and 1.
+ ///
+ /// To generate a thumbnail of an exact size, pass the desired size and
+ /// then scale to the final size using a traditional resampling algorithm.
+ pub fn scale(&mut self, requested_width: u16, requested_height: u16) -> Result<(u16, u16)> {
+ self.read_info()?;
+ let frame = self.frame.as_mut().unwrap();
+ let idct_size = crate::idct::choose_idct_size(
+ frame.image_size,
+ Dimensions {
+ width: requested_width,
+ height: requested_height,
+ },
+ );
+ frame.update_idct_size(idct_size)?;
+ Ok((frame.output_size.width, frame.output_size.height))
+ }
+
+ /// Decodes the image and returns the decoded pixels if successful.
+ pub fn decode(&mut self) -> Result<Vec<u8>> {
+ WorkerScope::with(|worker| self.decode_internal(false, worker))
+ }
+
+ fn decode_internal(
+ &mut self,
+ stop_after_metadata: bool,
+ worker_scope: &WorkerScope,
+ ) -> Result<Vec<u8>> {
+ if stop_after_metadata && self.frame.is_some() {
+ // The metadata has already been read.
+ return Ok(Vec::new());
+ } else if self.frame.is_none()
+ && (read_u8(&mut self.reader)? != 0xFF
+ || Marker::from_u8(read_u8(&mut self.reader)?) != Some(Marker::SOI))
+ {
+ return Err(Error::Format(
+ "first two bytes are not an SOI marker".to_owned(),
+ ));
+ }
+
+ let mut previous_marker = Marker::SOI;
+ let mut pending_marker = None;
+ let mut scans_processed = 0;
+ let mut planes = vec![
+ Vec::<u8>::new();
+ self.frame
+ .as_ref()
+ .map_or(0, |frame| frame.components.len())
+ ];
+ let mut planes_u16 = vec![
+ Vec::<u16>::new();
+ self.frame
+ .as_ref()
+ .map_or(0, |frame| frame.components.len())
+ ];
+
+ loop {
+ let marker = match pending_marker.take() {
+ Some(m) => m,
+ None => self.read_marker()?,
+ };
+
+ match marker {
+ // Frame header
+ Marker::SOF(..) => {
+ // Section 4.10
+ // "An image contains only one frame in the cases of sequential and
+ // progressive coding processes; an image contains multiple frames for the
+ // hierarchical mode."
+ if self.frame.is_some() {
+ return Err(Error::Unsupported(UnsupportedFeature::Hierarchical));
+ }
+
+ let frame = parse_sof(&mut self.reader, marker)?;
+ let component_count = frame.components.len();
+
+ if frame.is_differential {
+ return Err(Error::Unsupported(UnsupportedFeature::Hierarchical));
+ }
+ if frame.entropy_coding == EntropyCoding::Arithmetic {
+ return Err(Error::Unsupported(
+ UnsupportedFeature::ArithmeticEntropyCoding,
+ ));
+ }
+ if frame.precision != 8 && frame.coding_process != CodingProcess::Lossless {
+ return Err(Error::Unsupported(UnsupportedFeature::SamplePrecision(
+ frame.precision,
+ )));
+ }
+ if frame.precision != 8 && frame.precision != 16 {
+ return Err(Error::Unsupported(UnsupportedFeature::SamplePrecision(
+ frame.precision,
+ )));
+ }
+ if component_count != 1 && component_count != 3 && component_count != 4 {
+ return Err(Error::Unsupported(UnsupportedFeature::ComponentCount(
+ component_count as u8,
+ )));
+ }
+
+ // Make sure we support the subsampling ratios used.
+ let _ = Upsampler::new(
+ &frame.components,
+ frame.image_size.width,
+ frame.image_size.height,
+ )?;
+
+ self.frame = Some(frame);
+
+ if stop_after_metadata {
+ return Ok(Vec::new());
+ }
+
+ planes = vec![Vec::new(); component_count];
+ planes_u16 = vec![Vec::new(); component_count];
+ }
+
+ // Scan header
+ Marker::SOS => {
+ if self.frame.is_none() {
+ return Err(Error::Format("scan encountered before frame".to_owned()));
+ }
+
+ let frame = self.frame.clone().unwrap();
+ let scan = parse_sos(&mut self.reader, &frame)?;
+
+ if frame.coding_process == CodingProcess::DctProgressive
+ && self.coefficients.is_empty()
+ {
+ self.coefficients = frame
+ .components
+ .iter()
+ .map(|c| {
+ let block_count =
+ c.block_size.width as usize * c.block_size.height as usize;
+ vec![0; block_count * 64]
+ })
+ .collect();
+ }
+
+ if frame.coding_process == CodingProcess::Lossless {
+ let (marker, data) = self.decode_scan_lossless(&frame, &scan)?;
+
+ for (i, plane) in data
+ .into_iter()
+ .enumerate()
+ .filter(|&(_, ref plane)| !plane.is_empty())
+ {
+ planes_u16[i] = plane;
+ }
+ pending_marker = marker;
+ } else {
+ // This was previously buggy, so let's explain the log here a bit. When a
+ // progressive frame is encoded then the coefficients (DC, AC) of each
+ // component (=color plane) can be split amongst scans. In particular it can
+ // happen or at least occurs in the wild that a scan contains coefficient 0 of
+ // all components. If now one but not all components had all other coefficients
+ // delivered in previous scans then such a scan contains all components but
+ // completes only some of them! (This is technically NOT permitted for all
+ // other coefficients as the standard dictates that scans with coefficients
+ // other than the 0th must only contain ONE component so we would either
+ // complete it or not. We may want to detect and error in case more component
+ // are part of a scan than allowed.) What a weird edge case.
+ //
+ // But this means we track precisely which components get completed here.
+ let mut finished = [false; MAX_COMPONENTS];
+
+ if scan.successive_approximation_low == 0 {
+ for (&i, component_finished) in
+ scan.component_indices.iter().zip(&mut finished)
+ {
+ if self.coefficients_finished[i] == !0 {
+ continue;
+ }
+ for j in scan.spectral_selection.clone() {
+ self.coefficients_finished[i] |= 1 << j;
+ }
+ if self.coefficients_finished[i] == !0 {
+ *component_finished = true;
+ }
+ }
+ }
+
+ let preference =
+ Self::select_worker(&frame, PreferWorkerKind::Multithreaded);
+
+ let (marker, data) = worker_scope
+ .get_or_init_worker(preference, |worker| {
+ self.decode_scan(&frame, &scan, worker, &finished)
+ })?;
+
+ if let Some(data) = data {
+ for (i, plane) in data
+ .into_iter()
+ .enumerate()
+ .filter(|&(_, ref plane)| !plane.is_empty())
+ {
+ if self.coefficients_finished[i] == !0 {
+ planes[i] = plane;
+ }
+ }
+ }
+
+ pending_marker = marker;
+ }
+
+ scans_processed += 1;
+ }
+
+ // Table-specification and miscellaneous markers
+ // Quantization table-specification
+ Marker::DQT => {
+ let tables = parse_dqt(&mut self.reader)?;
+
+ for (i, &table) in tables.iter().enumerate() {
+ if let Some(table) = table {
+ let mut unzigzagged_table = [0u16; 64];
+
+ for j in 0..64 {
+ unzigzagged_table[UNZIGZAG[j] as usize] = table[j];
+ }
+
+ self.quantization_tables[i] = Some(Arc::new(unzigzagged_table));
+ }
+ }
+ }
+ // Huffman table-specification
+ Marker::DHT => {
+ let is_baseline = self.frame.as_ref().map(|frame| frame.is_baseline);
+ let (dc_tables, ac_tables) = parse_dht(&mut self.reader, is_baseline)?;
+
+ let current_dc_tables = mem::take(&mut self.dc_huffman_tables);
+ self.dc_huffman_tables = dc_tables
+ .into_iter()
+ .zip(current_dc_tables.into_iter())
+ .map(|(a, b)| a.or(b))
+ .collect();
+
+ let current_ac_tables = mem::take(&mut self.ac_huffman_tables);
+ self.ac_huffman_tables = ac_tables
+ .into_iter()
+ .zip(current_ac_tables.into_iter())
+ .map(|(a, b)| a.or(b))
+ .collect();
+ }
+ // Arithmetic conditioning table-specification
+ Marker::DAC => {
+ return Err(Error::Unsupported(
+ UnsupportedFeature::ArithmeticEntropyCoding,
+ ))
+ }
+ // Restart interval definition
+ Marker::DRI => self.restart_interval = parse_dri(&mut self.reader)?,
+ // Comment
+ Marker::COM => {
+ let _comment = parse_com(&mut self.reader)?;
+ }
+ // Application data
+ Marker::APP(..) => {
+ if let Some(data) = parse_app(&mut self.reader, marker)? {
+ match data {
+ AppData::Adobe(color_transform) => {
+ self.adobe_color_transform = Some(color_transform)
+ }
+ AppData::Jfif => {
+ // From the JFIF spec:
+ // "The APP0 marker is used to identify a JPEG FIF file.
+ // The JPEG FIF APP0 marker is mandatory right after the SOI marker."
+ // Some JPEGs in the wild does not follow this though, so we allow
+ // JFIF headers anywhere APP0 markers are allowed.
+ /*
+ if previous_marker != Marker::SOI {
+ return Err(Error::Format("the JFIF APP0 marker must come right after the SOI marker".to_owned()));
+ }
+ */
+
+ self.is_jfif = true;
+ }
+ AppData::Avi1 => self.is_mjpeg = true,
+ AppData::Icc(icc) => self.icc_markers.push(icc),
+ AppData::Exif(data) => self.exif_data = Some(data),
+ }
+ }
+ }
+ // Restart
+ Marker::RST(..) => {
+ // Some encoders emit a final RST marker after entropy-coded data, which
+ // decode_scan does not take care of. So if we encounter one, we ignore it.
+ if previous_marker != Marker::SOS {
+ return Err(Error::Format(
+ "RST found outside of entropy-coded data".to_owned(),
+ ));
+ }
+ }
+
+ // Define number of lines
+ Marker::DNL => {
+ // Section B.2.1
+ // "If a DNL segment (see B.2.5) is present, it shall immediately follow the first scan."
+ if previous_marker != Marker::SOS || scans_processed != 1 {
+ return Err(Error::Format(
+ "DNL is only allowed immediately after the first scan".to_owned(),
+ ));
+ }
+
+ return Err(Error::Unsupported(UnsupportedFeature::DNL));
+ }
+
+ // Hierarchical mode markers
+ Marker::DHP | Marker::EXP => {
+ return Err(Error::Unsupported(UnsupportedFeature::Hierarchical))
+ }
+
+ // End of image
+ Marker::EOI => break,
+
+ _ => {
+ return Err(Error::Format(format!(
+ "{:?} marker found where not allowed",
+ marker
+ )))
+ }
+ }
+
+ previous_marker = marker;
+ }
+
+ if self.frame.is_none() {
+ return Err(Error::Format(
+ "end of image encountered before frame".to_owned(),
+ ));
+ }
+
+ let frame = self.frame.as_ref().unwrap();
+ let preference = Self::select_worker(&frame, PreferWorkerKind::Multithreaded);
+
+ worker_scope.get_or_init_worker(preference, |worker| {
+ self.decode_planes(worker, planes, planes_u16)
+ })
+ }
+
+ fn decode_planes(
+ &mut self,
+ worker: &mut dyn Worker,
+ mut planes: Vec<Vec<u8>>,
+ planes_u16: Vec<Vec<u16>>,
+ ) -> Result<Vec<u8>> {
+ if self.frame.is_none() {
+ return Err(Error::Format(
+ "end of image encountered before frame".to_owned(),
+ ));
+ }
+
+ let frame = self.frame.as_ref().unwrap();
+
+ if {
+ let required_mem = frame
+ .components
+ .len()
+ .checked_mul(frame.output_size.width.into())
+ .and_then(|m| m.checked_mul(frame.output_size.height.into()));
+ required_mem.map_or(true, |m| self.decoding_buffer_size_limit < m)
+ } {
+ return Err(Error::Format(
+ "size of decoded image exceeds maximum allowed size".to_owned(),
+ ));
+ }
+
+ // If we're decoding a progressive jpeg and a component is unfinished, render what we've got
+ if frame.coding_process == CodingProcess::DctProgressive
+ && self.coefficients.len() == frame.components.len()
+ {
+ for (i, component) in frame.components.iter().enumerate() {
+ // Only dealing with unfinished components
+ if self.coefficients_finished[i] == !0 {
+ continue;
+ }
+
+ let quantization_table =
+ match self.quantization_tables[component.quantization_table_index].clone() {
+ Some(quantization_table) => quantization_table,
+ None => continue,
+ };
+
+ // Get the worker prepared
+ let row_data = RowData {
+ index: i,
+ component: component.clone(),
+ quantization_table,
+ };
+ worker.start(row_data)?;
+
+ // Send the rows over to the worker and collect the result
+ let coefficients_per_mcu_row = usize::from(component.block_size.width)
+ * usize::from(component.vertical_sampling_factor)
+ * 64;
+
+ let mut tasks = (0..frame.mcu_size.height).map(|mcu_y| {
+ let offset = usize::from(mcu_y) * coefficients_per_mcu_row;
+ let row_coefficients =
+ self.coefficients[i][offset..offset + coefficients_per_mcu_row].to_vec();
+ (i, row_coefficients)
+ });
+
+ // FIXME: additional potential work stealing opportunities for rayon case if we
+ // also internally can parallelize over components.
+ worker.append_rows(&mut tasks)?;
+ planes[i] = worker.get_result(i)?;
+ }
+ }
+
+ if frame.coding_process == CodingProcess::Lossless {
+ compute_image_lossless(frame, planes_u16)
+ } else {
+ compute_image(
+ &frame.components,
+ planes,
+ frame.output_size,
+ self.determine_color_transform(),
+ )
+ }
+ }
+
+ fn determine_color_transform(&self) -> ColorTransform {
+ if let Some(color_transform) = self.color_transform {
+ return color_transform;
+ }
+
+ let frame = self.frame.as_ref().unwrap();
+
+ if frame.components.len() == 1 {
+ return ColorTransform::Grayscale;
+ }
+
+ // Using logic for determining colour as described here: https://entropymine.wordpress.com/2018/10/22/how-is-a-jpeg-images-color-type-determined/
+
+ if frame.components.len() == 3 {
+ match (
+ frame.components[0].identifier,
+ frame.components[1].identifier,
+ frame.components[2].identifier,
+ ) {
+ (1, 2, 3) => {
+ return ColorTransform::YCbCr;
+ }
+ (1, 34, 35) => {
+ return ColorTransform::JcsBgYcc;
+ }
+ (82, 71, 66) => {
+ return ColorTransform::RGB;
+ }
+ (114, 103, 98) => {
+ return ColorTransform::JcsBgRgb;
+ }
+ _ => {}
+ }
+
+ if self.is_jfif {
+ return ColorTransform::YCbCr;
+ }
+ }
+
+ if let Some(colour_transform) = self.adobe_color_transform {
+ match colour_transform {
+ AdobeColorTransform::Unknown => {
+ if frame.components.len() == 3 {
+ return ColorTransform::RGB;
+ } else if frame.components.len() == 4 {
+ return ColorTransform::CMYK;
+ }
+ }
+ AdobeColorTransform::YCbCr => {
+ return ColorTransform::YCbCr;
+ }
+ AdobeColorTransform::YCCK => {
+ return ColorTransform::YCCK;
+ }
+ }
+ } else if frame.components.len() == 4 {
+ return ColorTransform::CMYK;
+ }
+
+ if frame.components.len() == 4 {
+ ColorTransform::YCCK
+ } else if frame.components.len() == 3 {
+ ColorTransform::YCbCr
+ } else {
+ ColorTransform::Unknown
+ }
+ }
+
+ fn read_marker(&mut self) -> Result<Marker> {
+ loop {
+ // This should be an error as the JPEG spec doesn't allow extraneous data between marker segments.
+ // libjpeg allows this though and there are images in the wild utilising it, so we are
+ // forced to support this behavior.
+ // Sony Ericsson P990i is an example of a device which produce this sort of JPEGs.
+ while read_u8(&mut self.reader)? != 0xFF {}
+
+ // Section B.1.1.2
+ // All markers are assigned two-byte codes: an X’FF’ byte followed by a
+ // byte which is not equal to 0 or X’FF’ (see Table B.1). Any marker may
+ // optionally be preceded by any number of fill bytes, which are bytes
+ // assigned code X’FF’.
+ let mut byte = read_u8(&mut self.reader)?;
+
+ // Section B.1.1.2
+ // "Any marker may optionally be preceded by any number of fill bytes, which are bytes assigned code X’FF’."
+ while byte == 0xFF {
+ byte = read_u8(&mut self.reader)?;
+ }
+
+ if byte != 0x00 && byte != 0xFF {
+ return Ok(Marker::from_u8(byte).unwrap());
+ }
+ }
+ }
+
+ fn decode_scan(
+ &mut self,
+ frame: &FrameInfo,
+ scan: &ScanInfo,
+ worker: &mut dyn Worker,
+ finished: &[bool; MAX_COMPONENTS],
+ ) -> Result<(Option<Marker>, Option<Vec<Vec<u8>>>)> {
+ assert!(scan.component_indices.len() <= MAX_COMPONENTS);
+
+ let components: Vec<Component> = scan
+ .component_indices
+ .iter()
+ .map(|&i| frame.components[i].clone())
+ .collect();
+
+ // Verify that all required quantization tables has been set.
+ if components
+ .iter()
+ .any(|component| self.quantization_tables[component.quantization_table_index].is_none())
+ {
+ return Err(Error::Format("use of unset quantization table".to_owned()));
+ }
+
+ if self.is_mjpeg {
+ fill_default_mjpeg_tables(
+ scan,
+ &mut self.dc_huffman_tables,
+ &mut self.ac_huffman_tables,
+ );
+ }
+
+ // Verify that all required huffman tables has been set.
+ if scan.spectral_selection.start == 0
+ && scan
+ .dc_table_indices
+ .iter()
+ .any(|&i| self.dc_huffman_tables[i].is_none())
+ {
+ return Err(Error::Format(
+ "scan makes use of unset dc huffman table".to_owned(),
+ ));
+ }
+ if scan.spectral_selection.end > 1
+ && scan
+ .ac_table_indices
+ .iter()
+ .any(|&i| self.ac_huffman_tables[i].is_none())
+ {
+ return Err(Error::Format(
+ "scan makes use of unset ac huffman table".to_owned(),
+ ));
+ }
+
+ // Prepare the worker thread for the work to come.
+ for (i, component) in components.iter().enumerate() {
+ if finished[i] {
+ let row_data = RowData {
+ index: i,
+ component: component.clone(),
+ quantization_table: self.quantization_tables
+ [component.quantization_table_index]
+ .clone()
+ .unwrap(),
+ };
+
+ worker.start(row_data)?;
+ }
+ }
+
+ let is_progressive = frame.coding_process == CodingProcess::DctProgressive;
+ let is_interleaved = components.len() > 1;
+ let mut dummy_block = [0i16; 64];
+ let mut huffman = HuffmanDecoder::new();
+ let mut dc_predictors = [0i16; MAX_COMPONENTS];
+ let mut mcus_left_until_restart = self.restart_interval;
+ let mut expected_rst_num = 0;
+ let mut eob_run = 0;
+ let mut mcu_row_coefficients = vec![vec![]; components.len()];
+
+ if !is_progressive {
+ for (i, component) in components.iter().enumerate().filter(|&(i, _)| finished[i]) {
+ let coefficients_per_mcu_row = component.block_size.width as usize
+ * component.vertical_sampling_factor as usize
+ * 64;
+ mcu_row_coefficients[i] = vec![0i16; coefficients_per_mcu_row];
+ }
+ }
+
+ // 4.8.2
+ // When reading from the stream, if the data is non-interleaved then an MCU consists of
+ // exactly one block (effectively a 1x1 sample).
+ let (mcu_horizontal_samples, mcu_vertical_samples) = if is_interleaved {
+ let horizontal = components
+ .iter()
+ .map(|component| component.horizontal_sampling_factor as u16)
+ .collect::<Vec<_>>();
+ let vertical = components
+ .iter()
+ .map(|component| component.vertical_sampling_factor as u16)
+ .collect::<Vec<_>>();
+ (horizontal, vertical)
+ } else {
+ (vec![1], vec![1])
+ };
+
+ // This also affects how many MCU values we read from stream. If it's a non-interleaved stream,
+ // the MCUs will be exactly the block count.
+ let (max_mcu_x, max_mcu_y) = if is_interleaved {
+ (frame.mcu_size.width, frame.mcu_size.height)
+ } else {
+ (
+ components[0].block_size.width,
+ components[0].block_size.height,
+ )
+ };
+
+ for mcu_y in 0..max_mcu_y {
+ if mcu_y * 8 >= frame.image_size.height {
+ break;
+ }
+
+ for mcu_x in 0..max_mcu_x {
+ if mcu_x * 8 >= frame.image_size.width {
+ break;
+ }
+
+ if self.restart_interval > 0 {
+ if mcus_left_until_restart == 0 {
+ match huffman.take_marker(&mut self.reader)? {
+ Some(Marker::RST(n)) => {
+ if n != expected_rst_num {
+ return Err(Error::Format(format!(
+ "found RST{} where RST{} was expected",
+ n, expected_rst_num
+ )));
+ }
+
+ huffman.reset();
+ // Section F.2.1.3.1
+ dc_predictors = [0i16; MAX_COMPONENTS];
+ // Section G.1.2.2
+ eob_run = 0;
+
+ expected_rst_num = (expected_rst_num + 1) % 8;
+ mcus_left_until_restart = self.restart_interval;
+ }
+ Some(marker) => {
+ return Err(Error::Format(format!(
+ "found marker {:?} inside scan where RST{} was expected",
+ marker, expected_rst_num
+ )))
+ }
+ None => {
+ return Err(Error::Format(format!(
+ "no marker found where RST{} was expected",
+ expected_rst_num
+ )))
+ }
+ }
+ }
+
+ mcus_left_until_restart -= 1;
+ }
+
+ for (i, component) in components.iter().enumerate() {
+ for v_pos in 0..mcu_vertical_samples[i] {
+ for h_pos in 0..mcu_horizontal_samples[i] {
+ let coefficients = if is_progressive {
+ let block_y = (mcu_y * mcu_vertical_samples[i] + v_pos) as usize;
+ let block_x = (mcu_x * mcu_horizontal_samples[i] + h_pos) as usize;
+ let block_offset =
+ (block_y * component.block_size.width as usize + block_x) * 64;
+ &mut self.coefficients[scan.component_indices[i]]
+ [block_offset..block_offset + 64]
+ } else if finished[i] {
+ // Because the worker thread operates in batches as if we were always interleaved, we
+ // need to distinguish between a single-shot buffer and one that's currently in process
+ // (for a non-interleaved) stream
+ let mcu_batch_current_row = if is_interleaved {
+ 0
+ } else {
+ mcu_y % component.vertical_sampling_factor as u16
+ };
+
+ let block_y = (mcu_batch_current_row * mcu_vertical_samples[i]
+ + v_pos) as usize;
+ let block_x = (mcu_x * mcu_horizontal_samples[i] + h_pos) as usize;
+ let block_offset =
+ (block_y * component.block_size.width as usize + block_x) * 64;
+ &mut mcu_row_coefficients[i][block_offset..block_offset + 64]
+ } else {
+ &mut dummy_block[..64]
+ }
+ .try_into()
+ .unwrap();
+
+ if scan.successive_approximation_high == 0 {
+ decode_block(
+ &mut self.reader,
+ coefficients,
+ &mut huffman,
+ self.dc_huffman_tables[scan.dc_table_indices[i]].as_ref(),
+ self.ac_huffman_tables[scan.ac_table_indices[i]].as_ref(),
+ scan.spectral_selection.clone(),
+ scan.successive_approximation_low,
+ &mut eob_run,
+ &mut dc_predictors[i],
+ )?;
+ } else {
+ decode_block_successive_approximation(
+ &mut self.reader,
+ coefficients,
+ &mut huffman,
+ self.ac_huffman_tables[scan.ac_table_indices[i]].as_ref(),
+ scan.spectral_selection.clone(),
+ scan.successive_approximation_low,
+ &mut eob_run,
+ )?;
+ }
+ }
+ }
+ }
+ }
+
+ // Send the coefficients from this MCU row to the worker thread for dequantization and idct.
+ for (i, component) in components.iter().enumerate() {
+ if finished[i] {
+ // In the event of non-interleaved streams, if we're still building the buffer out,
+ // keep going; don't send it yet. We also need to ensure we don't skip over the last
+ // row(s) of the image.
+ if !is_interleaved && (mcu_y + 1) * 8 < frame.image_size.height {
+ if (mcu_y + 1) % component.vertical_sampling_factor as u16 > 0 {
+ continue;
+ }
+ }
+
+ let coefficients_per_mcu_row = component.block_size.width as usize
+ * component.vertical_sampling_factor as usize
+ * 64;
+
+ let row_coefficients = if is_progressive {
+ // Because non-interleaved streams will have multiple MCU rows concatenated together,
+ // the row for calculating the offset is different.
+ let worker_mcu_y = if is_interleaved {
+ mcu_y
+ } else {
+ // Explicitly doing floor-division here
+ mcu_y / component.vertical_sampling_factor as u16
+ };
+
+ let offset = worker_mcu_y as usize * coefficients_per_mcu_row;
+ self.coefficients[scan.component_indices[i]]
+ [offset..offset + coefficients_per_mcu_row]
+ .to_vec()
+ } else {
+ mem::replace(
+ &mut mcu_row_coefficients[i],
+ vec![0i16; coefficients_per_mcu_row],
+ )
+ };
+
+ // FIXME: additional potential work stealing opportunities for rayon case if we
+ // also internally can parallelize over components.
+ worker.append_row((i, row_coefficients))?;
+ }
+ }
+ }
+
+ let mut marker = huffman.take_marker(&mut self.reader)?;
+ while let Some(Marker::RST(_)) = marker {
+ marker = self.read_marker().ok();
+ }
+
+ if finished.iter().any(|&c| c) {
+ // Retrieve all the data from the worker thread.
+ let mut data = vec![Vec::new(); frame.components.len()];
+
+ for (i, &component_index) in scan.component_indices.iter().enumerate() {
+ if finished[i] {
+ data[component_index] = worker.get_result(i)?;
+ }
+ }
+
+ Ok((marker, Some(data)))
+ } else {
+ Ok((marker, None))
+ }
+ }
+}
+
+fn decode_block<R: Read>(
+ reader: &mut R,
+ coefficients: &mut [i16; 64],
+ huffman: &mut HuffmanDecoder,
+ dc_table: Option<&HuffmanTable>,
+ ac_table: Option<&HuffmanTable>,
+ spectral_selection: Range<u8>,
+ successive_approximation_low: u8,
+ eob_run: &mut u16,
+ dc_predictor: &mut i16,
+) -> Result<()> {
+ debug_assert_eq!(coefficients.len(), 64);
+
+ if spectral_selection.start == 0 {
+ // Section F.2.2.1
+ // Figure F.12
+ let value = huffman.decode(reader, dc_table.unwrap())?;
+ let diff = match value {
+ 0 => 0,
+ 1..=11 => huffman.receive_extend(reader, value)?,
+ _ => {
+ // Section F.1.2.1.1
+ // Table F.1
+ return Err(Error::Format(
+ "invalid DC difference magnitude category".to_owned(),
+ ));
+ }
+ };
+
+ // Malicious JPEG files can cause this add to overflow, therefore we use wrapping_add.
+ // One example of such a file is tests/crashtest/images/dc-predictor-overflow.jpg
+ *dc_predictor = dc_predictor.wrapping_add(diff);
+ coefficients[0] = *dc_predictor << successive_approximation_low;
+ }
+
+ let mut index = cmp::max(spectral_selection.start, 1);
+
+ if index < spectral_selection.end && *eob_run > 0 {
+ *eob_run -= 1;
+ return Ok(());
+ }
+
+ // Section F.1.2.2.1
+ while index < spectral_selection.end {
+ if let Some((value, run)) = huffman.decode_fast_ac(reader, ac_table.unwrap())? {
+ index += run;
+
+ if index >= spectral_selection.end {
+ break;
+ }
+
+ coefficients[UNZIGZAG[index as usize] as usize] = value << successive_approximation_low;
+ index += 1;
+ } else {
+ let byte = huffman.decode(reader, ac_table.unwrap())?;
+ let r = byte >> 4;
+ let s = byte & 0x0f;
+
+ if s == 0 {
+ match r {
+ 15 => index += 16, // Run length of 16 zero coefficients.
+ _ => {
+ *eob_run = (1 << r) - 1;
+
+ if r > 0 {
+ *eob_run += huffman.get_bits(reader, r)?;
+ }
+
+ break;
+ }
+ }
+ } else {
+ index += r;
+
+ if index >= spectral_selection.end {
+ break;
+ }
+
+ coefficients[UNZIGZAG[index as usize] as usize] =
+ huffman.receive_extend(reader, s)? << successive_approximation_low;
+ index += 1;
+ }
+ }
+ }
+
+ Ok(())
+}
+
+fn decode_block_successive_approximation<R: Read>(
+ reader: &mut R,
+ coefficients: &mut [i16; 64],
+ huffman: &mut HuffmanDecoder,
+ ac_table: Option<&HuffmanTable>,
+ spectral_selection: Range<u8>,
+ successive_approximation_low: u8,
+ eob_run: &mut u16,
+) -> Result<()> {
+ debug_assert_eq!(coefficients.len(), 64);
+
+ let bit = 1 << successive_approximation_low;
+
+ if spectral_selection.start == 0 {
+ // Section G.1.2.1
+
+ if huffman.get_bits(reader, 1)? == 1 {
+ coefficients[0] |= bit;
+ }
+ } else {
+ // Section G.1.2.3
+
+ if *eob_run > 0 {
+ *eob_run -= 1;
+ refine_non_zeroes(reader, coefficients, huffman, spectral_selection, 64, bit)?;
+ return Ok(());
+ }
+
+ let mut index = spectral_selection.start;
+
+ while index < spectral_selection.end {
+ let byte = huffman.decode(reader, ac_table.unwrap())?;
+ let r = byte >> 4;
+ let s = byte & 0x0f;
+
+ let mut zero_run_length = r;
+ let mut value = 0;
+
+ match s {
+ 0 => {
+ match r {
+ 15 => {
+ // Run length of 16 zero coefficients.
+ // We don't need to do anything special here, zero_run_length is 15
+ // and then value (which is zero) gets written, resulting in 16
+ // zero coefficients.
+ }
+ _ => {
+ *eob_run = (1 << r) - 1;
+
+ if r > 0 {
+ *eob_run += huffman.get_bits(reader, r)?;
+ }
+
+ // Force end of block.
+ zero_run_length = 64;
+ }
+ }
+ }
+ 1 => {
+ if huffman.get_bits(reader, 1)? == 1 {
+ value = bit;
+ } else {
+ value = -bit;
+ }
+ }
+ _ => return Err(Error::Format("unexpected huffman code".to_owned())),
+ }
+
+ let range = Range {
+ start: index,
+ end: spectral_selection.end,
+ };
+ index = refine_non_zeroes(reader, coefficients, huffman, range, zero_run_length, bit)?;
+
+ if value != 0 {
+ coefficients[UNZIGZAG[index as usize] as usize] = value;
+ }
+
+ index += 1;
+ }
+ }
+
+ Ok(())
+}
+
+fn refine_non_zeroes<R: Read>(
+ reader: &mut R,
+ coefficients: &mut [i16; 64],
+ huffman: &mut HuffmanDecoder,
+ range: Range<u8>,
+ zrl: u8,
+ bit: i16,
+) -> Result<u8> {
+ debug_assert_eq!(coefficients.len(), 64);
+
+ let last = range.end - 1;
+ let mut zero_run_length = zrl;
+
+ for i in range {
+ let index = UNZIGZAG[i as usize] as usize;
+
+ let coefficient = &mut coefficients[index];
+
+ if *coefficient == 0 {
+ if zero_run_length == 0 {
+ return Ok(i);
+ }
+
+ zero_run_length -= 1;
+ } else if huffman.get_bits(reader, 1)? == 1 && *coefficient & bit == 0 {
+ if *coefficient > 0 {
+ *coefficient = coefficient
+ .checked_add(bit)
+ .ok_or_else(|| Error::Format("Coefficient overflow".to_owned()))?;
+ } else {
+ *coefficient = coefficient
+ .checked_sub(bit)
+ .ok_or_else(|| Error::Format("Coefficient overflow".to_owned()))?;
+ }
+ }
+ }
+
+ Ok(last)
+}
+
+fn compute_image(
+ components: &[Component],
+ mut data: Vec<Vec<u8>>,
+ output_size: Dimensions,
+ color_transform: ColorTransform,
+) -> Result<Vec<u8>> {
+ if data.is_empty() || data.iter().any(Vec::is_empty) {
+ return Err(Error::Format("not all components have data".to_owned()));
+ }
+
+ if components.len() == 1 {
+ let component = &components[0];
+ let mut decoded: Vec<u8> = data.remove(0);
+
+ let width = component.size.width as usize;
+ let height = component.size.height as usize;
+ let size = width * height;
+ let line_stride = component.block_size.width as usize * component.dct_scale;
+
+ // if the image width is a multiple of the block size,
+ // then we don't have to move bytes in the decoded data
+ if usize::from(output_size.width) != line_stride {
+ // The first line already starts at index 0, so we need to move only lines 1..height
+ // We move from the top down because all lines are being moved backwards.
+ for y in 1..height {
+ let destination_idx = y * width;
+ let source_idx = y * line_stride;
+ let end = source_idx + width;
+ decoded.copy_within(source_idx..end, destination_idx);
+ }
+ }
+ decoded.resize(size, 0);
+ Ok(decoded)
+ } else {
+ compute_image_parallel(components, data, output_size, color_transform)
+ }
+}
+
+pub(crate) fn choose_color_convert_func(
+ component_count: usize,
+ color_transform: ColorTransform,
+) -> Result<fn(&[Vec<u8>], &mut [u8])> {
+ match component_count {
+ 3 => match color_transform {
+ ColorTransform::None => Ok(color_no_convert),
+ ColorTransform::Grayscale => Err(Error::Format(
+ "Invalid number of channels (3) for Grayscale data".to_string(),
+ )),
+ ColorTransform::RGB => Ok(color_convert_line_rgb),
+ ColorTransform::YCbCr => Ok(color_convert_line_ycbcr),
+ ColorTransform::CMYK => Err(Error::Format(
+ "Invalid number of channels (3) for CMYK data".to_string(),
+ )),
+ ColorTransform::YCCK => Err(Error::Format(
+ "Invalid number of channels (3) for YCCK data".to_string(),
+ )),
+ ColorTransform::JcsBgYcc => Err(Error::Unsupported(
+ UnsupportedFeature::ColorTransform(ColorTransform::JcsBgYcc),
+ )),
+ ColorTransform::JcsBgRgb => Err(Error::Unsupported(
+ UnsupportedFeature::ColorTransform(ColorTransform::JcsBgRgb),
+ )),
+ ColorTransform::Unknown => Err(Error::Format("Unknown colour transform".to_string())),
+ },
+ 4 => match color_transform {
+ ColorTransform::None => Ok(color_no_convert),
+ ColorTransform::Grayscale => Err(Error::Format(
+ "Invalid number of channels (4) for Grayscale data".to_string(),
+ )),
+ ColorTransform::RGB => Err(Error::Format(
+ "Invalid number of channels (4) for RGB data".to_string(),
+ )),
+ ColorTransform::YCbCr => Err(Error::Format(
+ "Invalid number of channels (4) for YCbCr data".to_string(),
+ )),
+ ColorTransform::CMYK => Ok(color_convert_line_cmyk),
+ ColorTransform::YCCK => Ok(color_convert_line_ycck),
+
+ ColorTransform::JcsBgYcc => Err(Error::Unsupported(
+ UnsupportedFeature::ColorTransform(ColorTransform::JcsBgYcc),
+ )),
+ ColorTransform::JcsBgRgb => Err(Error::Unsupported(
+ UnsupportedFeature::ColorTransform(ColorTransform::JcsBgRgb),
+ )),
+ ColorTransform::Unknown => Err(Error::Format("Unknown colour transform".to_string())),
+ },
+ _ => panic!(),
+ }
+}
+
+fn color_convert_line_rgb(data: &[Vec<u8>], output: &mut [u8]) {
+ assert!(data.len() == 3, "wrong number of components for rgb");
+ let [r, g, b]: &[Vec<u8>; 3] = data.try_into().unwrap();
+ for (((chunk, r), g), b) in output
+ .chunks_exact_mut(3)
+ .zip(r.iter())
+ .zip(g.iter())
+ .zip(b.iter())
+ {
+ chunk[0] = *r;
+ chunk[1] = *g;
+ chunk[2] = *b;
+ }
+}
+
+fn color_convert_line_ycbcr(data: &[Vec<u8>], output: &mut [u8]) {
+ assert!(data.len() == 3, "wrong number of components for ycbcr");
+ let [y, cb, cr]: &[_; 3] = data.try_into().unwrap();
+
+ #[cfg(not(feature = "platform_independent"))]
+ let arch_specific_pixels = {
+ if let Some(ycbcr) = crate::arch::get_color_convert_line_ycbcr() {
+ #[allow(unsafe_code)]
+ unsafe {
+ ycbcr(y, cb, cr, output)
+ }
+ } else {
+ 0
+ }
+ };
+
+ #[cfg(feature = "platform_independent")]
+ let arch_specific_pixels = 0;
+
+ for (((chunk, y), cb), cr) in output
+ .chunks_exact_mut(3)
+ .zip(y.iter())
+ .zip(cb.iter())
+ .zip(cr.iter())
+ .skip(arch_specific_pixels)
+ {
+ let (r, g, b) = ycbcr_to_rgb(*y, *cb, *cr);
+ chunk[0] = r;
+ chunk[1] = g;
+ chunk[2] = b;
+ }
+}
+
+fn color_convert_line_ycck(data: &[Vec<u8>], output: &mut [u8]) {
+ assert!(data.len() == 4, "wrong number of components for ycck");
+ let [c, m, y, k]: &[Vec<u8>; 4] = data.try_into().unwrap();
+
+ for ((((chunk, c), m), y), k) in output
+ .chunks_exact_mut(4)
+ .zip(c.iter())
+ .zip(m.iter())
+ .zip(y.iter())
+ .zip(k.iter())
+ {
+ let (r, g, b) = ycbcr_to_rgb(*c, *m, *y);
+ chunk[0] = r;
+ chunk[1] = g;
+ chunk[2] = b;
+ chunk[3] = 255 - *k;
+ }
+}
+
+fn color_convert_line_cmyk(data: &[Vec<u8>], output: &mut [u8]) {
+ assert!(data.len() == 4, "wrong number of components for cmyk");
+ let [c, m, y, k]: &[Vec<u8>; 4] = data.try_into().unwrap();
+
+ for ((((chunk, c), m), y), k) in output
+ .chunks_exact_mut(4)
+ .zip(c.iter())
+ .zip(m.iter())
+ .zip(y.iter())
+ .zip(k.iter())
+ {
+ chunk[0] = 255 - c;
+ chunk[1] = 255 - m;
+ chunk[2] = 255 - y;
+ chunk[3] = 255 - k;
+ }
+}
+
+fn color_no_convert(data: &[Vec<u8>], output: &mut [u8]) {
+ let mut output_iter = output.iter_mut();
+
+ for pixel in data {
+ for d in pixel {
+ *(output_iter.next().unwrap()) = *d;
+ }
+ }
+}
+
+const FIXED_POINT_OFFSET: i32 = 20;
+const HALF: i32 = (1 << FIXED_POINT_OFFSET) / 2;
+
+// ITU-R BT.601
+// Based on libjpeg-turbo's jdcolext.c
+fn ycbcr_to_rgb(y: u8, cb: u8, cr: u8) -> (u8, u8, u8) {
+ let y = y as i32 * (1 << FIXED_POINT_OFFSET) + HALF;
+ let cb = cb as i32 - 128;
+ let cr = cr as i32 - 128;
+
+ let r = clamp_fixed_point(y + stbi_f2f(1.40200) * cr);
+ let g = clamp_fixed_point(y - stbi_f2f(0.34414) * cb - stbi_f2f(0.71414) * cr);
+ let b = clamp_fixed_point(y + stbi_f2f(1.77200) * cb);
+ (r, g, b)
+}
+
+fn stbi_f2f(x: f32) -> i32 {
+ (x * ((1 << FIXED_POINT_OFFSET) as f32) + 0.5) as i32
+}
+
+fn clamp_fixed_point(value: i32) -> u8 {
+ (value >> FIXED_POINT_OFFSET).min(255).max(0) as u8
+}
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