Struct PngDecoder

pub struct PngDecoder<R>
where
    R: BufRead + Seek,
{ /* private fields */ }

Available on crate feature dep_image only.

PNG decoder

Implementations

impl<R> PngDecoder<R>

where R: BufRead + Seek,

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

Creates a new decoder that decodes from the stream r

pub fn with_limits(r: R, limits: Limits) -> Result<PngDecoder<R>, ImageError>

Creates a new decoder that decodes from the stream r with the given limits.

pub fn gamma_value(&self) -> Result<Option<f64>, ImageError>

Returns the gamma value of the image or None if no gamma value is indicated.

If an sRGB chunk is present this method returns a gamma value of 0.45455 and ignores the value in the gAMA chunk. This is the recommended behavior according to the PNG standard:

When the sRGB chunk is present, […] decoders that recognize the sRGB chunk but are not capable of colour management are recommended to ignore the gAMA and cHRM chunks, and use the values given above as if they had appeared in gAMA and cHRM chunks.

pub fn apng(self) -> Result<ApngDecoder<R>, ImageError>

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) -> Result<bool, ImageError>

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<R> ImageDecoder for PngDecoder<R>

where R: BufRead + Seek,

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 icc_profile(&mut self) -> Result<Option<Vec<u8>>, ImageError>

Returns the ICC color profile embedded in the image, or Ok(None) if the image does not have one.

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

Returns all the bytes in the image.

fn read_image_boxed( self: Box<PngDecoder<R>>, buf: &mut [u8], ) -> Result<(), ImageError>

Use read_image instead; this method is an implementation detail needed so the trait can be object safe.

fn set_limits(&mut self, limits: Limits) -> Result<(), ImageError>

Set the decoder to have the specified limits. See Limits for the different kinds of limits that is possible to set.

fn original_color_type(&self) -> ExtendedColorType

Returns the color type of the image file before decoding

fn exif_metadata(&mut self) -> Result<Option<Vec<u8>>, ImageError>

Returns the raw Exif chunk, if it is present. A third-party crate such as kamadak-exif is required to actually parse it.

fn orientation(&mut self) -> Result<Orientation, ImageError>

Returns the orientation of the image.

fn total_bytes(&self) -> u64

Returns the total number of bytes in the decoded image.