Struct JpegEncoder 

pub struct JpegEncoder { /* private fields */ }

Encodes a baseline JPEG stream.

Implementations

impl JpegEncoder

pub const fn new() -> Self

An encoder at the default quality.

pub fn with_quality(quality: u8) -> Result<Self>

An encoder at an explicit quality, 1..=100.

Chroma subsampling follows quality, as it does in every encoder that exposes one number: 4:4:4 from 90 up, 4:2:0 below. Above 90 the subsampling, not the quantization, becomes the dominant loss, so keeping it on would make the quality number stop meaning anything.

Errors

Returns PixelsError::InvalidArgument unless quality is 1..=100.

pub const fn with_subsampling(self, subsampling: Subsampling) -> Self

Override the chroma subsampling chosen by quality.

pub const fn with_progressive(self, progressive: bool) -> Self

Write a progressive file (sharp’s progressive): a viewer shows a coarse picture first and sharpens it as the rest arrives, and the per-scan tables usually make it a few percent smaller. The whole image’s coefficients are held until Encoder::finish.

pub const fn progressive(&self) -> bool

Whether this encoder writes a progressive file.

pub fn from_options(options: &EncodeOptions) -> Self

An encoder configured from generic encode options: quality, progressive, and chroma_subsampling in place of the one quality implies.

pub const fn subsampling(&self) -> Subsampling

The chosen chroma subsampling.

Trait Implementations

impl Debug for JpegEncoder

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

Formats the value using the given formatter.

impl Default for JpegEncoder

fn default() -> Self

Returns the “default value” for a type.

impl Encoder for JpegEncoder

fn set_exif(&mut self, exif: Option<&[u8]>) -> Result<()>

The block goes in an APP1 segment, which holds at most 65,527 bytes after its Exif\0\0 identifier. A larger block, which no JPEG could have carried, is not written, as libvips drops it.

fn set_xmp(&mut self, xmp: Option<&[u8]>) -> Result<()>

The packet goes in one APP1 segment, which holds at most 65,504 bytes after its identifier; a larger one is not written (extended XMP, spread over several segments, is not).

fn set_density(&mut self, density: Option<Density>) -> Result<()>

Written in the JFIF header, rounded to whole pixels per inch or centimetre.

fn set_icc_profile(&mut self, profile: Option<&[u8]>) -> Result<()>

Embed profile as the image’s ICC colour profile, or write none.

fn write_header( &mut self, desc: &ImageDescriptor, sink: &mut dyn Sink, ) -> Result<()>

Begin an image, writing any container header.

fn write_row(&mut self, row: &[u8], sink: &mut dyn Sink) -> Result<()>

Write the next row, top to bottom.

fn finish(&mut self, sink: &mut dyn Sink) -> Result<()>

Finish the image, writing any trailer and flushing the sink.