Enum turbojpeg::Subsamp

#[non_exhaustive]
#[repr(i32)]
pub enum Subsamp {
    None = 0,
    Sub2x1 = 1,
    Sub2x2 = 2,
    Gray = 3,
    Sub1x2 = 4,
    Sub4x1 = 5,
    Sub1x4 = 6,
}

Chrominance subsampling options.

When pixels are converted from RGB to YCbCr or from CMYK to YCCK as part of the JPEG compression process, some of the Cb and Cr (chrominance) components can be discarded or averaged together to produce a smaller image with little perceptible loss of image clarity (the human eye is more sensitive to small changes in brightness than to small changes in color). This is called “chrominance subsampling”.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

None = 0

No chrominance subsampling (4:4:4);

The JPEG or YUV image will contain one chrominance component for every pixel in the source image.

Sub2x1 = 1

2x1 chrominance subsampling (4:2:2).

The JPEG or YUV image will contain one chrominance component for every 2x1 block of pixels in the source image.

Sub2x2 = 2

2x2 chrominance subsampling (4:2:0).

The JPEG or YUV image will contain one chrominance component for every 2x2 block of pixels in the source image.

Gray = 3

Grayscale.

The JPEG or YUV image will contain no chrominance components.

Sub1x2 = 4

1x2 chrominance subsampling (4:4:0).

The JPEG or YUV image will contain one chrominance component for every 1x2 block of pixels in the source image.

Note

4:4:0 subsampling is not fully accelerated in libjpeg-turbo.

Sub4x1 = 5

4x1 chrominance subsampling (4:1:1).

The JPEG or YUV image will contain one chrominance component for every 4x1 block of pixels in the source image. JPEG images compressed with 4:1:1 subsampling will be almost exactly the same size as those compressed with 4:2:0 subsampling, and in the aggregate, both subsampling methods produce approximately the same perceptual quality. However, 4:1:1 is better able to reproduce sharp horizontal features.

Note

4:1:1 subsampling is not fully accelerated in libjpeg-turbo.

Sub1x4 = 6

1x4 chrominance subsampling (4:4:1).

The JPEG or YUV image will contain one chrominance component for every 1x4 block of pixels in the source image. JPEG images compressed with 4:4:1 subsampling will be almost exactly the same size as those compressed with 4:2:0 subsampling, and in the aggregate, both subsampling methods produce approximately the same perceptual quality. However, 4:4:1 is better able to reproduce sharp vertical features.

Note

4:4:1 subsampling is not fully accelerated in libjpeg-turbo.

Implementations

impl Subsamp

pub fn mcu_width(self) -> usize

Get the width of the MCU block for this level of chrominance subsampling.

This is equal to 8 * self.width().

Example

assert_eq!(turbojpeg::Subsamp::Sub2x1.mcu_width(), 16);

pub fn mcu_height(self) -> usize

Get the height of the MCU block for this level of chrominance subsampling.

This is equal to 8 * self.height().

Example

assert_eq!(turbojpeg::Subsamp::Sub2x1.mcu_height(), 8);

pub fn mcu_size(self) -> (usize, usize)

Get the size of the MCU block for this level of chrominance subsampling as (width, height).

Example

assert_eq!(turbojpeg::Subsamp::Sub2x1.mcu_size(), (16, 8));

pub fn width(self) -> usize

Get the horizontal subsampling factor.

Example

assert_eq!(turbojpeg::Subsamp::Sub2x1.width(), 2);

pub fn height(self) -> usize

Get the vertical subsampling factor.

Example

assert_eq!(turbojpeg::Subsamp::Sub2x1.height(), 1);

pub fn size(self) -> (usize, usize)

Get the horizontal and vertical subsampling factors.

Example

assert_eq!(turbojpeg::Subsamp::Sub2x1.size(), (2, 1));

Trait Implementations

impl Clone for Subsamp

fn clone(&self) -> Subsamp

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Subsamp

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Hash for Subsamp

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for Subsamp

fn cmp(&self, other: &Subsamp) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized + PartialOrd,

Restrict a value to a certain interval.

impl PartialEq for Subsamp

fn eq(&self, other: &Subsamp) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for Subsamp

fn partial_cmp(&self, other: &Subsamp) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl Copy for Subsamp

impl Eq for Subsamp

impl StructuralPartialEq for Subsamp