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Move ImageAlphaType into being ImageFormats instead #125

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Move ImageAlphaType into being ImageFormats instead #125

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25 changes: 8 additions & 17 deletions src/image.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,10 +9,14 @@ use super::{Blob, Extend};
#[non_exhaustive]
#[repr(u8)]
pub enum ImageFormat {
/// 32-bit RGBA with 8-bit channels.
/// 32-bit RGBA with 8-bit channels, with a separate alpha.
Rgba8 = 0,
/// 32-bit BGRA with 8-bit channels.
Bgra8 = 1,
/// 32-bit RGBA with 8-bit channels, with premultiplied alpha.
PremulRgba8 = 1,
/// 32-bit BGRA with 8-bit channels, with a separate alpha.
Bgra8 = 2,
/// 32-bit BGRA with 8-bit channels, with premultiplied alpha.
PremulBgra8 = 3,
// NOTICE: If a new value is added, be sure to update the bytemuck CheckedBitPattern impl.
}

Expand All @@ -24,24 +28,13 @@ impl ImageFormat {
#[must_use]
pub fn size_in_bytes(self, width: u32, height: u32) -> Option<usize> {
match self {
Self::Rgba8 | Self::Bgra8 => 4_usize
Self::Rgba8 | Self::PremulRgba8 | Self::Bgra8 | Self::PremulBgra8 => 4_usize
.checked_mul(width as usize)
.and_then(|x| x.checked_mul(height as usize)),
}
}
}

/// Handling of alpha channel.
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
#[repr(u8)]
pub enum ImageAlphaType {
/// Image has separate alpha channel (also called straight/unpremultiplied alpha).
Alpha = 0,
/// Image has colors with premultiplied alpha.
AlphaPremultiplied = 1,
}

/// Defines the desired quality for sampling an image.
#[derive(Copy, Clone, PartialEq, Eq, Default, Debug)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
Expand Down Expand Up @@ -71,8 +64,6 @@ pub struct ImageData {
pub data: Blob<u8>,
/// Pixel format of the image.
pub format: ImageFormat,
/// Encoding of alpha in the image pixels.
pub alpha_type: ImageAlphaType,
/// Width of the image.
pub width: u32,
/// Height of the image.
Expand Down
81 changes: 4 additions & 77 deletions src/impl_bytemuck.rs
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Expand Up @@ -3,7 +3,7 @@

#![allow(unsafe_code, reason = "unsafe is required for bytemuck unsafe impls")]

use crate::{Compose, Extend, Fill, ImageAlphaType, ImageFormat, ImageQuality, Mix};
use crate::{Compose, Extend, Fill, ImageFormat, ImageQuality, Mix};

// Safety: The enum is `repr(u8)` and has only fieldless variants.
unsafe impl bytemuck::NoUninit for Compose {}
Expand Down Expand Up @@ -102,32 +102,7 @@ unsafe impl bytemuck::checked::CheckedBitPattern for ImageFormat {
unsafe impl bytemuck::Contiguous for ImageFormat {
type Int = u8;
const MIN_VALUE: u8 = Self::Rgba8 as u8;
const MAX_VALUE: u8 = Self::Bgra8 as u8;
}

// Safety: The enum is `repr(u8)` and has only fieldless variants.
unsafe impl bytemuck::NoUninit for ImageAlphaType {}

// Safety: The enum is `repr(u8)` and `0` is a valid value.
unsafe impl bytemuck::Zeroable for ImageAlphaType {}

// Safety: The enum is `repr(u8)`.
unsafe impl bytemuck::checked::CheckedBitPattern for ImageAlphaType {
type Bits = u8;

fn is_valid_bit_pattern(bits: &u8) -> bool {
use bytemuck::Contiguous;
// Don't need to compare against MIN_VALUE as this is u8 and 0 is the MIN_VALUE.
*bits <= Self::MAX_VALUE
}
}

// Safety: The enum is `repr(u8)`. All values are `u8` and fall within
// the min and max values.
unsafe impl bytemuck::Contiguous for ImageAlphaType {
type Int = u8;
const MIN_VALUE: u8 = Self::Alpha as u8;
const MAX_VALUE: u8 = Self::AlphaPremultiplied as u8;
const MAX_VALUE: u8 = Self::PremulBgra8 as u8;
}

// Safety: The enum is `repr(u8)` and has only fieldless variants.
Expand Down Expand Up @@ -172,7 +147,7 @@ unsafe impl bytemuck::checked::CheckedBitPattern for Mix {

#[cfg(test)]
mod tests {
use crate::{Compose, Extend, Fill, ImageAlphaType, ImageFormat, ImageQuality, Mix};
use crate::{Compose, Extend, Fill, ImageFormat, ImageQuality, Mix};
use bytemuck::{checked::try_from_bytes, Contiguous, Zeroable};
use core::ptr;

Expand All @@ -191,22 +166,14 @@ mod tests {
assert_eq!(Ok(&Fill::EvenOdd), try_from_bytes::<Fill>(valid_one));
assert!(try_from_bytes::<Fill>(invalid).is_err());

assert_eq!(
Ok(&ImageAlphaType::Alpha),
try_from_bytes::<ImageAlphaType>(valid_zero)
);
assert_eq!(
Ok(&ImageAlphaType::AlphaPremultiplied),
try_from_bytes::<ImageAlphaType>(valid_one)
);
assert!(try_from_bytes::<ImageFormat>(invalid).is_err());

assert_eq!(
Ok(&ImageFormat::Rgba8),
try_from_bytes::<ImageFormat>(valid_zero)
);
assert_eq!(
Ok(&ImageFormat::Bgra8),
Ok(&ImageFormat::PremulRgba8),
try_from_bytes::<ImageFormat>(valid_one)
);
assert!(try_from_bytes::<ImageFormat>(invalid).is_err());
Expand Down Expand Up @@ -245,11 +212,6 @@ mod tests {
let image_format_2 = ImageFormat::from_integer(image_format_1.into_integer());
assert_eq!(Some(image_format_1), image_format_2);

let image_alpha_type_1 = ImageAlphaType::Alpha;
let image_alpha_type_2 = ImageAlphaType::from_integer(image_alpha_type_1.into_integer());
assert_eq!(Some(image_alpha_type_1), image_alpha_type_2);
assert_eq!(None, ImageAlphaType::from_integer(255));

let image_quality_1 = ImageQuality::Low;
let image_quality_2 = ImageQuality::from_integer(image_quality_1.into_integer());
assert_eq!(Some(image_quality_1), image_quality_2);
Expand All @@ -271,9 +233,6 @@ mod tests {
let image_format = ImageFormat::zeroed();
assert_eq!(image_format, ImageFormat::Rgba8);

let image_alpha_type = ImageAlphaType::zeroed();
assert_eq!(image_alpha_type, ImageAlphaType::Alpha);

let image_quality = ImageQuality::zeroed();
assert_eq!(image_quality, ImageQuality::Low);

Expand Down Expand Up @@ -337,20 +296,6 @@ mod tests {
}
};

/// Tests that the [`Contiguous`] impl for [`ImageAlphaType`] is not trivially incorrect.
const _: () = {
let mut value = 0;
while value <= ImageAlphaType::MAX_VALUE {
// Safety: In a const context, therefore if this makes an invalid ImageFormat, that will be detected.
let it: ImageAlphaType = unsafe { ptr::read((&raw const value).cast()) };
// Evaluate the enum value to ensure it actually has a valid tag
if it as u8 != value {
unreachable!();
}
value += 1;
}
};

/// Tests that the [`Contiguous`] impl for [`ImageQuality`] is not trivially incorrect.
const _: () = {
let mut value = 0;
Expand Down Expand Up @@ -443,24 +388,6 @@ mod doctests {
/// ```
const _IMAGE_FORMAT: () = {};

/// Validates that any new variants in `ImageAlphaType` has led to a change in the `Contiguous` impl.
/// Note that to test this robustly, we'd need 256 tests, which is impractical.
/// We make the assumption that all new variants will maintain contiguousness.
///
/// ```compile_fail,E0080
/// use bytemuck::Contiguous;
/// use peniko::ImageAlphaType;
/// const {
/// let value = ImageAlphaType::MAX_VALUE + 1;
/// let it: ImageAlphaType = unsafe { core::ptr::read((&raw const value).cast()) };
/// // Evaluate the enum value to ensure it actually has an invalid tag
/// if it as u8 != value {
/// unreachable!();
/// }
/// }
/// ```
const _IMAGE_ALPHA_TYPE: () = {};

/// Validates that any new variants in `ImageQuality` has led to a change in the `Contiguous` impl.
/// Note that to test this robustly, we'd need 256 tests, which is impractical.
/// We make the assumption that all new variants will maintain contiguousness.
Expand Down
4 changes: 1 addition & 3 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -51,9 +51,7 @@ pub use gradient::{
ColorStop, ColorStops, ColorStopsSource, Gradient, GradientKind, LinearGradientPosition,
RadialGradientPosition, SweepGradientPosition,
};
pub use image::{
ImageAlphaType, ImageBrush, ImageBrushRef, ImageData, ImageFormat, ImageQuality, ImageSampler,
};
pub use image::{ImageBrush, ImageBrushRef, ImageData, ImageFormat, ImageQuality, ImageSampler};
pub use style::{Fill, Style, StyleRef};

/// A convenient alias for the color type used for [`Brush`].
Expand Down
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