Struct matrix_qrcode::image::png::PngDecoder

pub struct PngDecoder<R> where
    R: Read,  { /* private fields */ }

PNG decoder

Implementations

impl<R> PngDecoder<R> where
    R: Read, 

pub fn new(r: R) -> Result<PngDecoder<R>, ImageError>

Creates a new decoder that decodes from the stream r

pub fn apng(self) -> ApngDecoder<R>

Turn this into an iterator over the animation frames.

Reading the complete animation requires more memory than reading the data from the IDAT frame–multiple frame buffers need to be reserved at the same time. We further do not support compositing 16-bit colors. In any case this would be lossy as the interface of animation decoders does not support 16-bit colors.

If something is not supported or a limit is violated then the decoding step that requires them will fail and an error will be returned instead of the frame. No further frames will be returned.

pub fn is_apng(&self) -> bool

Returns if the image contains an animation.

Note that the file itself decides if the default image is considered to be part of the animation. When it is not the common interpretation is to use it as a thumbnail.

If a non-animated image is converted into an ApngDecoder then its iterator is empty.

Trait Implementations

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

type Reader = PngReader<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
) -> Result<<PngDecoder<R> as ImageDecoder<'a>>::Reader, ImageError>

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]) -> Result<(), ImageError>

Returns all the bytes in the 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 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 read_image_with_progress<F>(
    self,
    buf: &mut [u8],
    progress_callback: F
) -> Result<(), ImageError> where
    F: Fn(Progress), 

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