/src/image/src/codecs/avif/encoder.rs

Source
//! Encoding of AVIF images.
///
/// The [AVIF] specification defines an image derivative of the AV1 bitstream, an open video codec.
///
/// [AVIF]: https://aomediacodec.github.io/av1-avif/
use std::borrow::Cow;
use std::cmp::min;
use std::io::Write;
use std::mem::size_of;

use crate::color::{FromColor, Luma, LumaA, Rgb, Rgba};
use crate::error::{
    EncodingError, ParameterError, ParameterErrorKind, UnsupportedError, UnsupportedErrorKind,
};
use crate::{ExtendedColorType, ImageBuffer, ImageEncoder, ImageFormat, Pixel};
use crate::{ImageError, ImageResult};

use bytemuck::{try_cast_slice, try_cast_slice_mut, Pod, PodCastError};
use num_traits::Zero;
use ravif::{BitDepth, Encoder, Img, RGB8, RGBA8};
use rgb::AsPixels;

/// AVIF Encoder.
///
/// Writes one image into the chosen output.
pub struct AvifEncoder<W> {
    inner: W,
    encoder: Encoder<'static>,
}

/// An enumeration over supported AVIF color spaces
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub enum ColorSpace {
    /// sRGB colorspace
    Srgb,
    /// BT.709 colorspace
    Bt709,
}

impl ColorSpace {
    fn to_ravif(self) -> ravif::ColorModel {
        match self {
            Self::Srgb => ravif::ColorModel::RGB,
            Self::Bt709 => ravif::ColorModel::YCbCr,
        }
    }
}

enum RgbColor<'buf> {
    Rgb8(Img<&'buf [RGB8]>),
    Rgba8(Img<&'buf [RGBA8]>),
}

impl<W: Write> AvifEncoder<W> {
    /// Create a new encoder that writes its output to `w`.
    pub fn new(w: W) -> Self {
        AvifEncoder::new_with_speed_quality(w, 4, 80) // `cavif` uses these defaults
    }

    /// Create a new encoder with a specified speed and quality that writes its output to `w`.
    /// `speed` accepts a value in the range 1-10, where 1 is the slowest and 10 is the fastest.
    /// Slower speeds generally yield better compression results.
    /// `quality` accepts a value in the range 1-100, where 1 is the worst and 100 is the best.
    pub fn new_with_speed_quality(w: W, speed: u8, quality: u8) -> Self {
        // Clamp quality and speed to range
        let quality = min(quality, 100);
        let speed = min(speed, 10);

        let encoder = Encoder::new()
            .with_quality(f32::from(quality))
            .with_alpha_quality(f32::from(quality))
            .with_speed(speed)
            .with_bit_depth(BitDepth::Eight);

        AvifEncoder { inner: w, encoder }
    }

    /// Encode with the specified `color_space`.
    pub fn with_colorspace(mut self, color_space: ColorSpace) -> Self {
        self.encoder = self
            .encoder
            .with_internal_color_model(color_space.to_ravif());
        self
    }

    /// Configures `rayon` thread pool size.
    /// The default `None` is to use all threads in the default `rayon` thread pool.
    pub fn with_num_threads(mut self, num_threads: Option<usize>) -> Self {
        self.encoder = self.encoder.with_num_threads(num_threads);
        self
    }
}

impl<W: Write> ImageEncoder for AvifEncoder<W> {
    /// Encode image data with the indicated color type.
    ///
    /// The encoder currently requires all data to be RGBA8, it will be converted internally if
    /// necessary. When data is suitably aligned, i.e. u16 channels to two bytes, then the
    /// conversion may be more efficient.
    #[track_caller]
    fn write_image(
        mut self,
        data: &[u8],
        width: u32,
        height: u32,
        color: ExtendedColorType,
    ) -> ImageResult<()> {
        let expected_buffer_len = color.buffer_size(width, height);
        assert_eq!(
            expected_buffer_len,
            data.len() as u64,
            "Invalid buffer length: expected {expected_buffer_len} got {} for {width}x{height} image",
            data.len(),
        );

        self.set_color(color);
        // `ravif` needs strongly typed data so let's convert. We can either use a temporarily
        // owned version in our own buffer or zero-copy if possible by using the input buffer.
        // This requires going through `rgb`.
        let mut fallback = vec![]; // This vector is used if we need to do a color conversion.
        let result = match Self::encode_as_img(&mut fallback, data, width, height, color)? {
            RgbColor::Rgb8(buffer) => self.encoder.encode_rgb(buffer),
            RgbColor::Rgba8(buffer) => self.encoder.encode_rgba(buffer),
        };
        let data = result.map_err(|err| {
            ImageError::Encoding(EncodingError::new(ImageFormat::Avif.into(), err))
        })?;
        self.inner.write_all(&data.avif_file)?;
        Ok(())
    }

    fn set_exif_metadata(&mut self, exif: Vec<u8>) -> Result<(), UnsupportedError> {
        // encoder.with_exif() accepts Self rather than &mut self, and Encoder doesn't impl Default,
        // so we can't even mem::take it and have to do this instead
        let encoder = std::mem::replace(&mut self.encoder, Encoder::new());
        self.encoder = encoder.with_exif(exif);
        Ok(())
    }
}

impl<W: Write> AvifEncoder<W> {
    // Does not currently do anything. Mirrors behaviour of old config function.
    fn set_color(&mut self, _color: ExtendedColorType) {
        // self.config.color_space = ColorSpace::RGB;
    }

    fn encode_as_img<'buf>(
        fallback: &'buf mut Vec<u8>,
        data: &'buf [u8],
        width: u32,
        height: u32,
        color: ExtendedColorType,
    ) -> ImageResult<RgbColor<'buf>> {
        // Error wrapping utility for color dependent buffer dimensions.
        fn try_from_raw<P: Pixel>(
            data: &[P::Subpixel],
            width: u32,
            height: u32,
        ) -> ImageResult<ImageBuffer<P, &[P::Subpixel]>> {
            ImageBuffer::from_raw(width, height, data).ok_or_else(|| {
                ImageError::Parameter(ParameterError::from_kind(
                    ParameterErrorKind::DimensionMismatch,
                ))
            })
        }

        // Convert to target color type using few buffer allocations.
        fn convert_into<'buf, P>(
            buf: &'buf mut Vec<u8>,
            image: ImageBuffer<P, &[P::Subpixel]>,
        ) -> Img<&'buf [RGBA8]>
        where
            P: Pixel,
            Rgba<u8>: FromColor<P>,
        {
            let (width, height) = image.dimensions();
            // TODO: conversion re-using the target buffer?
            let image: ImageBuffer<Rgba<u8>, _> = image.convert();
            *buf = image.into_raw();
            Img::new(buf.as_pixels(), width as usize, height as usize)
        }

        // Cast the input slice using few buffer allocations if possible.
        // In particular try not to allocate if the caller did the infallible reverse.
        fn cast_buffer<Channel>(buf: &[u8]) -> ImageResult<Cow<'_, [Channel]>>
        where
            Channel: Pod + Zero,
        {
            match try_cast_slice(buf) {
                Ok(slice) => Ok(Cow::Borrowed(slice)),
                Err(PodCastError::OutputSliceWouldHaveSlop) => Err(ImageError::Parameter(
                    ParameterError::from_kind(ParameterErrorKind::DimensionMismatch),
                )),
                Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned) => {
                    // Sad, but let's allocate.
                    // bytemuck checks alignment _before_ slop but size mismatch before this..
                    if !buf.len().is_multiple_of(size_of::<Channel>()) {
                        Err(ImageError::Parameter(ParameterError::from_kind(
                            ParameterErrorKind::DimensionMismatch,
                        )))
                    } else {
                        let len = buf.len() / size_of::<Channel>();
                        let mut data = vec![Channel::zero(); len];
                        let view = try_cast_slice_mut::<_, u8>(data.as_mut_slice()).unwrap();
                        view.copy_from_slice(buf);
                        Ok(Cow::Owned(data))
                    }
                }
                Err(err) => {
                    // Are you trying to encode a ZST??
                    Err(ImageError::Parameter(ParameterError::from_kind(
                        ParameterErrorKind::Generic(format!("{err:?}")),
                    )))
                }
            }
        }

        match color {
            ExtendedColorType::Rgb8 => {
                // ravif doesn't do any checks but has some asserts, so we do the checks.
                let img = try_from_raw::<Rgb<u8>>(data, width, height)?;
                // Now, internally ravif uses u32 but it takes usize. We could do some checked
                // conversion but instead we use that a non-empty image must be addressable.
                if img.pixels().is_empty() {
                    return Err(ImageError::Parameter(ParameterError::from_kind(
                        ParameterErrorKind::DimensionMismatch,
                    )));
                }

                Ok(RgbColor::Rgb8(Img::new(
                    AsPixels::as_pixels(data),
                    width as usize,
                    height as usize,
                )))
            }
            ExtendedColorType::Rgba8 => {
                // ravif doesn't do any checks but has some asserts, so we do the checks.
                let img = try_from_raw::<Rgba<u8>>(data, width, height)?;
                // Now, internally ravif uses u32 but it takes usize. We could do some checked
                // conversion but instead we use that a non-empty image must be addressable.
                if img.pixels().is_empty() {
                    return Err(ImageError::Parameter(ParameterError::from_kind(
                        ParameterErrorKind::DimensionMismatch,
                    )));
                }

                Ok(RgbColor::Rgba8(Img::new(
                    AsPixels::as_pixels(data),
                    width as usize,
                    height as usize,
                )))
            }
            // we need a separate buffer..
            ExtendedColorType::L8 => {
                let image = try_from_raw::<Luma<u8>>(data, width, height)?;
                Ok(RgbColor::Rgba8(convert_into(fallback, image)))
            }
            ExtendedColorType::La8 => {
                let image = try_from_raw::<LumaA<u8>>(data, width, height)?;
                Ok(RgbColor::Rgba8(convert_into(fallback, image)))
            }
            // we need to really convert data..
            ExtendedColorType::L16 => {
                let buffer = cast_buffer(data)?;
                let image = try_from_raw::<Luma<u16>>(&buffer, width, height)?;
                Ok(RgbColor::Rgba8(convert_into(fallback, image)))
            }
            ExtendedColorType::La16 => {
                let buffer = cast_buffer(data)?;
                let image = try_from_raw::<LumaA<u16>>(&buffer, width, height)?;
                Ok(RgbColor::Rgba8(convert_into(fallback, image)))
            }
            ExtendedColorType::Rgb16 => {
                let buffer = cast_buffer(data)?;
                let image = try_from_raw::<Rgb<u16>>(&buffer, width, height)?;
                Ok(RgbColor::Rgba8(convert_into(fallback, image)))
            }
            ExtendedColorType::Rgba16 => {
                let buffer = cast_buffer(data)?;
                let image = try_from_raw::<Rgba<u16>>(&buffer, width, height)?;
                Ok(RgbColor::Rgba8(convert_into(fallback, image)))
            }
            // for cases we do not support at all?
            _ => Err(ImageError::Unsupported(
                UnsupportedError::from_format_and_kind(
                    ImageFormat::Avif.into(),
                    UnsupportedErrorKind::Color(color),
                ),
            )),
        }
    }
}

Coverage Report

Created: 2026-08-14 08:22

Line	Count	Source
1		//! Encoding of AVIF images.
2		///
3		/// The [AVIF] specification defines an image derivative of the AV1 bitstream, an open video codec.
4		///
5		/// [AVIF]: https://aomediacodec.github.io/av1-avif/
6		use std::borrow::Cow;
7		use std::cmp::min;
8		use std::io::Write;
9		use std::mem::size_of;
10
11		use crate::color::{FromColor, Luma, LumaA, Rgb, Rgba};
12		use crate::error::{
13		EncodingError, ParameterError, ParameterErrorKind, UnsupportedError, UnsupportedErrorKind,
14		};
15		use crate::{ExtendedColorType, ImageBuffer, ImageEncoder, ImageFormat, Pixel};
16		use crate::{ImageError, ImageResult};
17
18		use bytemuck::{try_cast_slice, try_cast_slice_mut, Pod, PodCastError};
19		use num_traits::Zero;
20		use ravif::{BitDepth, Encoder, Img, RGB8, RGBA8};
21		use rgb::AsPixels;
22
23		/// AVIF Encoder.
24		///
25		/// Writes one image into the chosen output.
26		pub struct AvifEncoder<W> {
27		inner: W,
28		encoder: Encoder<'static>,
29		}
30
31		/// An enumeration over supported AVIF color spaces
32		#[derive(Debug, Copy, Clone, PartialEq, Eq)]
33		#[non_exhaustive]
34		pub enum ColorSpace {
35		/// sRGB colorspace
36		Srgb,
37		/// BT.709 colorspace
38		Bt709,
39		}
40
41		impl ColorSpace {
42	0	fn to_ravif(self) -> ravif::ColorModel {
43	0	match self {
44	0	Self::Srgb => ravif::ColorModel::RGB,
45	0	Self::Bt709 => ravif::ColorModel::YCbCr,
46		}
47	0	}
48		}
49
50		enum RgbColor<'buf> {
51		Rgb8(Img<&'buf [RGB8]>),
52		Rgba8(Img<&'buf [RGBA8]>),
53		}
54
55		impl<W: Write> AvifEncoder<W> {
56		/// Create a new encoder that writes its output to `w`.
57	0	pub fn new(w: W) -> Self {
58	0	AvifEncoder::new_with_speed_quality(w, 4, 80) // `cavif` uses these defaults
59	0	} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::new Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<&mut std::io::cursor::Cursor<alloc::vec::Vec<u8>>>>::new
60
61		/// Create a new encoder with a specified speed and quality that writes its output to `w`.
62		/// `speed` accepts a value in the range 1-10, where 1 is the slowest and 10 is the fastest.
63		/// Slower speeds generally yield better compression results.
64		/// `quality` accepts a value in the range 1-100, where 1 is the worst and 100 is the best.
65	0	pub fn new_with_speed_quality(w: W, speed: u8, quality: u8) -> Self {
66		// Clamp quality and speed to range
67	0	let quality = min(quality, 100);
68	0	let speed = min(speed, 10);
69
70	0	let encoder = Encoder::new()
71	0	.with_quality(f32::from(quality))
72	0	.with_alpha_quality(f32::from(quality))
73	0	.with_speed(speed)
74	0	.with_bit_depth(BitDepth::Eight);
75
76	0	AvifEncoder { inner: w, encoder }
77	0	} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::new_with_speed_quality Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<&mut std::io::cursor::Cursor<alloc::vec::Vec<u8>>>>::new_with_speed_quality
78
79		/// Encode with the specified `color_space`.
80	0	pub fn with_colorspace(mut self, color_space: ColorSpace) -> Self {
81	0	self.encoder = self
82	0	.encoder
83	0	.with_internal_color_model(color_space.to_ravif());
84	0	self
85	0	}
86
87		/// Configures `rayon` thread pool size.
88		/// The default `None` is to use all threads in the default `rayon` thread pool.
89	0	pub fn with_num_threads(mut self, num_threads: Option<usize>) -> Self {
90	0	self.encoder = self.encoder.with_num_threads(num_threads);
91	0	self
92	0	}
93		}
94
95		impl<W: Write> ImageEncoder for AvifEncoder<W> {
96		/// Encode image data with the indicated color type.
97		///
98		/// The encoder currently requires all data to be RGBA8, it will be converted internally if
99		/// necessary. When data is suitably aligned, i.e. u16 channels to two bytes, then the
100		/// conversion may be more efficient.
101		#[track_caller]
102	0	fn write_image(
103	0	mut self,
104	0	data: &[u8],
105	0	width: u32,
106	0	height: u32,
107	0	color: ExtendedColorType,
108	0	) -> ImageResult<()> {
109	0	let expected_buffer_len = color.buffer_size(width, height);
110	0	assert_eq!(
111		expected_buffer_len,
112	0	data.len() as u64,
113	0	"Invalid buffer length: expected {expected_buffer_len} got {} for {width}x{height} image",
114	0	data.len(),
115		);
116
117	0	self.set_color(color);
118		// `ravif` needs strongly typed data so let's convert. We can either use a temporarily
119		// owned version in our own buffer or zero-copy if possible by using the input buffer.
120		// This requires going through `rgb`.
121	0	let mut fallback = vec![]; // This vector is used if we need to do a color conversion.
122	0	let result = match Self::encode_as_img(&mut fallback, data, width, height, color)? {
123	0	RgbColor::Rgb8(buffer) => self.encoder.encode_rgb(buffer),
124	0	RgbColor::Rgba8(buffer) => self.encoder.encode_rgba(buffer),
125		};
126	0	let data = result.map_err(\|err\| {
127	0	ImageError::Encoding(EncodingError::new(ImageFormat::Avif.into(), err))
128	0	})?; Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_> as image::io::encoder::ImageEncoder>::write_image::{closure#0} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<&mut std::io::cursor::Cursor<alloc::vec::Vec<u8>>> as image::io::encoder::ImageEncoder>::write_image::{closure#0}
129	0	self.inner.write_all(&data.avif_file)?;
130	0	Ok(())
131	0	} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_> as image::io::encoder::ImageEncoder>::write_image Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<&mut std::io::cursor::Cursor<alloc::vec::Vec<u8>>> as image::io::encoder::ImageEncoder>::write_image
132
133	0	fn set_exif_metadata(&mut self, exif: Vec<u8>) -> Result<(), UnsupportedError> {
134		// encoder.with_exif() accepts Self rather than &mut self, and Encoder doesn't impl Default,
135		// so we can't even mem::take it and have to do this instead
136	0	let encoder = std::mem::replace(&mut self.encoder, Encoder::new());
137	0	self.encoder = encoder.with_exif(exif);
138	0	Ok(())
139	0	} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_> as image::io::encoder::ImageEncoder>::set_exif_metadata Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<&mut std::io::cursor::Cursor<alloc::vec::Vec<u8>>> as image::io::encoder::ImageEncoder>::set_exif_metadata
140		}
141
142		impl<W: Write> AvifEncoder<W> {
143		// Does not currently do anything. Mirrors behaviour of old config function.
144	0	fn set_color(&mut self, _color: ExtendedColorType) {
145		// self.config.color_space = ColorSpace::RGB;
146	0	} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::set_color Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<&mut std::io::cursor::Cursor<alloc::vec::Vec<u8>>>>::set_color
147
148	0	fn encode_as_img<'buf>(
149	0	fallback: &'buf mut Vec<u8>,
150	0	data: &'buf [u8],
151	0	width: u32,
152	0	height: u32,
153	0	color: ExtendedColorType,
154	0	) -> ImageResult<RgbColor<'buf>> {
155		// Error wrapping utility for color dependent buffer dimensions.
156	0	fn try_from_raw<P: Pixel>(
157	0	data: &[P::Subpixel],
158	0	width: u32,
159	0	height: u32,
160	0	) -> ImageResult<ImageBuffer<P, &[P::Subpixel]>> {
161	0	ImageBuffer::from_raw(width, height, data).ok_or_else(\|\| {
162	0	ImageError::Parameter(ParameterError::from_kind(
163	0	ParameterErrorKind::DimensionMismatch,
164	0	))
165	0	}) Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<_>::{closure#0} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::Rgb<u8>>::{closure#0} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::Rgb<u16>>::{closure#0} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::Luma<u8>>::{closure#0} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::Luma<u16>>::{closure#0} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::Rgba<u8>>::{closure#0} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::Rgba<u16>>::{closure#0} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::LumaA<u8>>::{closure#0} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::LumaA<u16>>::{closure#0}
166	0	} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<_> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::Rgb<u8>> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::Rgb<u16>> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::Luma<u8>> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::Luma<u16>> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::Rgba<u8>> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::Rgba<u16>> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::LumaA<u8>> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::try_from_raw::<image::color::LumaA<u16>>
167
168		// Convert to target color type using few buffer allocations.
169	0	fn convert_into<'buf, P>(
170	0	buf: &'buf mut Vec<u8>,
171	0	image: ImageBuffer<P, &[P::Subpixel]>,
172	0	) -> Img<&'buf [RGBA8]>
173	0	where
174	0	P: Pixel,
175	0	Rgba<u8>: FromColor<P>,
176		{
177	0	let (width, height) = image.dimensions();
178		// TODO: conversion re-using the target buffer?
179	0	let image: ImageBuffer<Rgba<u8>, _> = image.convert();
180	0	*buf = image.into_raw();
181	0	Img::new(buf.as_pixels(), width as usize, height as usize)
182	0	} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::convert_into::<_> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::convert_into::<image::color::Rgb<u16>> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::convert_into::<image::color::Luma<u8>> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::convert_into::<image::color::Luma<u16>> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::convert_into::<image::color::Rgba<u16>> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::convert_into::<image::color::LumaA<u8>> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::convert_into::<image::color::LumaA<u16>>
183
184		// Cast the input slice using few buffer allocations if possible.
185		// In particular try not to allocate if the caller did the infallible reverse.
186	0	fn cast_buffer<Channel>(buf: &[u8]) -> ImageResult<Cow<'_, [Channel]>>
187	0	where
188	0	Channel: Pod + Zero,
189		{
190	0	match try_cast_slice(buf) {
191	0	Ok(slice) => Ok(Cow::Borrowed(slice)),
192	0	Err(PodCastError::OutputSliceWouldHaveSlop) => Err(ImageError::Parameter(
193	0	ParameterError::from_kind(ParameterErrorKind::DimensionMismatch),
194	0	)),
195		Err(PodCastError::TargetAlignmentGreaterAndInputNotAligned) => {
196		// Sad, but let's allocate.
197		// bytemuck checks alignment _before_ slop but size mismatch before this..
198	0	if !buf.len().is_multiple_of(size_of::<Channel>()) {
199	0	Err(ImageError::Parameter(ParameterError::from_kind(
200	0	ParameterErrorKind::DimensionMismatch,
201	0	)))
202		} else {
203	0	let len = buf.len() / size_of::<Channel>();
204	0	let mut data = vec![Channel::zero(); len];
205	0	let view = try_cast_slice_mut::<_, u8>(data.as_mut_slice()).unwrap();
206	0	view.copy_from_slice(buf);
207	0	Ok(Cow::Owned(data))
208		}
209		}
210	0	Err(err) => {
211		// Are you trying to encode a ZST??
212	0	Err(ImageError::Parameter(ParameterError::from_kind(
213	0	ParameterErrorKind::Generic(format!("{err:?}")),
214	0	)))
215		}
216		}
217	0	} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::cast_buffer::<_> Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img::cast_buffer::<u16>
218
219	0	match color {
220		ExtendedColorType::Rgb8 => {
221		// ravif doesn't do any checks but has some asserts, so we do the checks.
222	0	let img = try_from_raw::<Rgb<u8>>(data, width, height)?;
223		// Now, internally ravif uses u32 but it takes usize. We could do some checked
224		// conversion but instead we use that a non-empty image must be addressable.
225	0	if img.pixels().is_empty() {
226	0	return Err(ImageError::Parameter(ParameterError::from_kind(
227	0	ParameterErrorKind::DimensionMismatch,
228	0	)));
229	0	}
230
231	0	Ok(RgbColor::Rgb8(Img::new(
232	0	AsPixels::as_pixels(data),
233	0	width as usize,
234	0	height as usize,
235	0	)))
236		}
237		ExtendedColorType::Rgba8 => {
238		// ravif doesn't do any checks but has some asserts, so we do the checks.
239	0	let img = try_from_raw::<Rgba<u8>>(data, width, height)?;
240		// Now, internally ravif uses u32 but it takes usize. We could do some checked
241		// conversion but instead we use that a non-empty image must be addressable.
242	0	if img.pixels().is_empty() {
243	0	return Err(ImageError::Parameter(ParameterError::from_kind(
244	0	ParameterErrorKind::DimensionMismatch,
245	0	)));
246	0	}
247
248	0	Ok(RgbColor::Rgba8(Img::new(
249	0	AsPixels::as_pixels(data),
250	0	width as usize,
251	0	height as usize,
252	0	)))
253		}
254		// we need a separate buffer..
255		ExtendedColorType::L8 => {
256	0	let image = try_from_raw::<Luma<u8>>(data, width, height)?;
257	0	Ok(RgbColor::Rgba8(convert_into(fallback, image)))
258		}
259		ExtendedColorType::La8 => {
260	0	let image = try_from_raw::<LumaA<u8>>(data, width, height)?;
261	0	Ok(RgbColor::Rgba8(convert_into(fallback, image)))
262		}
263		// we need to really convert data..
264		ExtendedColorType::L16 => {
265	0	let buffer = cast_buffer(data)?;
266	0	let image = try_from_raw::<Luma<u16>>(&buffer, width, height)?;
267	0	Ok(RgbColor::Rgba8(convert_into(fallback, image)))
268		}
269		ExtendedColorType::La16 => {
270	0	let buffer = cast_buffer(data)?;
271	0	let image = try_from_raw::<LumaA<u16>>(&buffer, width, height)?;
272	0	Ok(RgbColor::Rgba8(convert_into(fallback, image)))
273		}
274		ExtendedColorType::Rgb16 => {
275	0	let buffer = cast_buffer(data)?;
276	0	let image = try_from_raw::<Rgb<u16>>(&buffer, width, height)?;
277	0	Ok(RgbColor::Rgba8(convert_into(fallback, image)))
278		}
279		ExtendedColorType::Rgba16 => {
280	0	let buffer = cast_buffer(data)?;
281	0	let image = try_from_raw::<Rgba<u16>>(&buffer, width, height)?;
282	0	Ok(RgbColor::Rgba8(convert_into(fallback, image)))
283		}
284		// for cases we do not support at all?
285	0	_ => Err(ImageError::Unsupported(
286	0	UnsupportedError::from_format_and_kind(
287	0	ImageFormat::Avif.into(),
288	0	UnsupportedErrorKind::Color(color),
289	0	),
290	0	)),
291		}
292	0	} Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<_>>::encode_as_img Unexecuted instantiation: <image::codecs::avif::encoder::AvifEncoder<&mut std::io::cursor::Cursor<alloc::vec::Vec<u8>>>>::encode_as_img
293		}