Struct WebPDecoder 

pub struct WebPDecoder { /* private fields */ }

Decodes a WebP stream.

Implementations

impl WebPDecoder

pub fn new<S: Source>(source: S, limits: Limits) -> Result<Self>

Read the file and parse its container; the pixels decode when the first row is read.

The whole file is read here: chunks may come in any order the container allows, so the size, alpha, orientation and ICC profile are only known once every chunk has been seen. Decoding the bitstream is what costs, and it waits, so opening a WebP to ask its size or metadata is a header parse. The image then decodes in one piece: neither bitstream yields finished rows from a prefix of the file without the decoder holding its whole working state.

Errors

Returns PixelsError::Malformed for a container or bitstream header it rejects, PixelsError::Unsupported for a WebP feature it does not implement, or PixelsError::LimitExceeded if the image exceeds limits. A bitstream that is damaged past its header is reported by the first Decoder::read_row.

Trait Implementations

impl Debug for WebPDecoder

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

Formats the value using the given formatter.

impl Decoder for WebPDecoder

fn descriptor(&self) -> ImageDescriptor

The shape of the image, known after the header is parsed.

fn orientation(&self) -> Orientation

How the stored image must be turned to display upright, as its metadata declares.

fn icc_profile(&self) -> Option<&[u8]>

The embedded ICC colour profile, if the file carries one.

fn animation(&self) -> Option<Animation>

The source’s animation, if it has more than one frame.

fn capability(&self) -> DecodeCapability

What this decoder can produce without a full decode.

fn read_row(&mut self, out: &mut [u8]) -> Result<()>

Decode the next row, top to bottom, into out.

fn read_region( &mut self, region: Region, out: &mut TileMut<'_>, ) -> Result<(), PixelsError>

Decode an arbitrary region into out.

fn reduced_descriptor(&self, target: (u32, u32)) -> Option<ImageDescriptor>

What this decoder would produce if asked for target or larger, when the format lets it reach that size more cheaply than a full decode.

fn reduce_to(&mut self, descriptor: ImageDescriptor) -> Result<(), PixelsError>

Commit to producing descriptor, which Decoder::reduced_descriptor must have returned.