pub struct Reader<R: Read> { /* private fields */ }
Expand description
A multi-format image reader.
Wraps an input reader to facilitate automatic detection of an image’s format, appropriate
decoding method, and dispatches into the set of supported ImageDecoder
implementations.
Usage
Opening a file, deducing the format based on the file path automatically, and trying to decode the image contained can be performed by constructing the reader and immediately consuming it.
let image = Reader::open("path/to/image.png")?
.decode()?;
It is also possible to make a guess based on the content. This is especially handy if the
source is some blob in memory and you have constructed the reader in another way. Here is an
example with a pnm
black-and-white subformat that encodes its pixel matrix with ascii values.
use std::io::Cursor;
use image::ImageFormat;
let raw_data = b"P1 2 2\n\
0 1\n\
1 0\n";
let mut reader = Reader::new(Cursor::new(raw_data))
.with_guessed_format()
.expect("Cursor io never fails");
assert_eq!(reader.format(), Some(ImageFormat::Pnm));
let image = reader.decode()?;
As a final fallback or if only a specific format must be used, the reader always allows manual
specification of the supposed image format with set_format
.
Implementations
sourceimpl<R: Read> Reader<R>
impl<R: Read> Reader<R>
sourcepub fn new(reader: R) -> Self
pub fn new(reader: R) -> Self
Create a new image reader without a preset format.
It is possible to guess the format based on the content of the read object with
with_guessed_format
, or to set the format directly with set_format
.
sourcepub fn with_format(reader: R, format: ImageFormat) -> Self
pub fn with_format(reader: R, format: ImageFormat) -> Self
Construct a reader with specified format.
sourcepub fn format(&self) -> Option<ImageFormat>
pub fn format(&self) -> Option<ImageFormat>
Get the currently determined format.
sourcepub fn set_format(&mut self, format: ImageFormat)
pub fn set_format(&mut self, format: ImageFormat)
Supply the format as which to interpret the read image.
sourcepub fn clear_format(&mut self)
pub fn clear_format(&mut self)
Remove the current information on the image format.
Note that many operations require format information to be present and will return e.g. an
ImageError::Unsupported
when the image format has not been set.
sourcepub fn into_inner(self) -> R
pub fn into_inner(self) -> R
Unwrap the reader.
sourceimpl Reader<BufReader<File>>
impl Reader<BufReader<File>>
sourcepub fn open<P>(path: P) -> Result<Self>where
P: AsRef<Path>,
pub fn open<P>(path: P) -> Result<Self>where
P: AsRef<Path>,
Open a file to read, format will be guessed from path.
This will not attempt any io operation on the opened file.
If you want to inspect the content for a better guess on the format, which does not depend
on file extensions, follow this call with a call to with_guessed_format
.
sourceimpl<R: BufRead + Seek> Reader<R>
impl<R: BufRead + Seek> Reader<R>
sourcepub fn with_guessed_format(self) -> Result<Self>
pub fn with_guessed_format(self) -> Result<Self>
Make a format guess based on the content, replacing it on success.
Returns Ok
with the guess if no io error occurs. Additionally, replaces the current
format if the guess was successful. If the guess was unable to determine a format then
the current format of the reader is unchanged.
Returns an error if the underlying reader fails. The format is unchanged. The error is a
std::io::Error
and not ImageError
since the only error case is an error when the
underlying reader seeks.
When an error occurs, the reader may not have been properly reset and it is potentially hazardous to continue with more io.
Usage
This supplements the path based type deduction from open
with content based deduction.
This is more common in Linux and UNIX operating systems and also helpful if the path can
not be directly controlled.
let image = Reader::open("image.unknown")?
.with_guessed_format()?
.decode()?;
sourcepub fn into_dimensions(self) -> ImageResult<(u32, u32)>
pub fn into_dimensions(self) -> ImageResult<(u32, u32)>
Read the image dimensions.
Uses the current format to construct the correct reader for the format.
If no format was determined, returns an ImageError::Unsupported
.
sourcepub fn decode(self) -> ImageResult<DynamicImage>
pub fn decode(self) -> ImageResult<DynamicImage>
Read the image (replaces load
).
Uses the current format to construct the correct reader for the format.
If no format was determined, returns an ImageError::Unsupported
.