Struct image::codecs::jpeg::JpegDecoder

pub struct JpegDecoder<R> { /* private fields */ }

JPEG decoder

Implementations

impl<R: Read> JpegDecoder<R>

pub fn new(r: R) -> ImageResult<JpegDecoder<R>>

Create a new decoder that decodes from the stream r

pub fn scale(
    &mut self,
    requested_width: u16,
    requested_height: u16
) -> ImageResult<(u16, u16)>

Configure the decoder to scale the image during decoding.

This efficiently scales the image by the smallest supported scale factor that produces an image larger than or equal to the requested size in at least one axis. The currently implemented scale factors are 1/8, 1/4, 1/2 and 1.

To generate a thumbnail of an exact size, pass the desired size and then scale to the final size using a traditional resampling algorithm.

The size of the image to be loaded, with the scale factor applied, is returned.

Trait Implementations

impl<'a, R: 'a + Read> ImageDecoder<'a> for JpegDecoder<R>

type Reader = JpegReader<R>

The type of reader produced by into_reader.

fn dimensions(&self) -> (u32, u32)

Returns a tuple containing the width and height of the image

fn color_type(&self) -> ColorType

Returns the color type of the image data produced by this decoder

fn into_reader(self) -> ImageResult<Self::Reader>

Returns a reader that can be used to obtain the bytes of the image. For the best performance, always try to read at least scanline_bytes from the reader at a time. Reading fewer bytes will cause the reader to perform internal buffering.

fn read_image(self, buf: &mut [u8]) -> ImageResult<()>

Returns all the bytes in the image.

fn original_color_type(&self) -> ExtendedColorType

Retuns the color type of the image file before decoding

fn total_bytes(&self) -> u64

Returns the total number of bytes in the decoded image.

fn scanline_bytes(&self) -> u64

Returns the minimum number of bytes that can be efficiently read from this decoder. This may be as few as 1 or as many as total_bytes().

fn read_image_with_progress<F: Fn(Progress)>(
    self,
    buf: &mut [u8],
    progress_callback: F
) -> ImageResult<()>

Same as read_image but periodically calls the provided callback to give updates on loading progress.