Enum turbojpeg::Subsamp

#[repr(u32)]
pub enum Subsamp {
    None,
    Sub2x1,
    Sub2x2,
    Gray,
    Sub1x2,
    Sub4x1,
}

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

None

No chrominance subsampling (4:4:4);

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

Sub2x1

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

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

Grayscale.

The JPEG or YUV image will contain no chrominance components.

Sub1x2

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

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.

Implementations

impl Subsamp

pub fn from_u32(subsamp: u32) -> Result<Subsamp>

Trait Implementations

impl Clone for Subsamp

fn clone(&self) -> Subsamp

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Copy for Subsamp

impl Debug for Subsamp

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

Formats the value using the given formatter.

impl Eq for Subsamp

impl Hash for Subsamp

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

Feeds this value into the given Hasher.

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

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.

#[must_use]

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

Compares and returns the maximum of two values.

#[must_use]

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

Compares and returns the minimum of two values.

#[must_use]

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

Restrict a value to a certain interval.

impl PartialEq<Subsamp> for Subsamp

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

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

#[must_use]

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

This method tests for !=.

impl PartialOrd<Subsamp> for Subsamp

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

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

#[must_use]

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

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

#[must_use]

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

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

#[must_use]

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

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

#[must_use]

pub 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 StructuralEq for Subsamp

impl StructuralPartialEq for Subsamp