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use std::convert::TryFrom;
use std::io::{self, Cursor, Read};
use std::marker::PhantomData;
use std::mem;
use crate::color::ColorType;
use crate::image::ImageDecoder;
use crate::error::{ImageError, ImageResult};
pub struct JpegDecoder<R> {
decoder: jpeg::Decoder<R>,
metadata: jpeg::ImageInfo,
}
impl<R: Read> JpegDecoder<R> {
pub fn new(r: R) -> ImageResult<JpegDecoder<R>> {
let mut decoder = jpeg::Decoder::new(r);
decoder.read_info().map_err(ImageError::from_jpeg)?;
let mut metadata = decoder.info().unwrap();
if metadata.pixel_format == jpeg::PixelFormat::CMYK32 {
metadata.pixel_format = jpeg::PixelFormat::RGB24;
}
Ok(JpegDecoder {
decoder,
metadata,
})
}
}
pub struct JpegReader<R>(Cursor<Vec<u8>>, PhantomData<R>);
impl<R> Read for JpegReader<R> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
self.0.read(buf)
}
fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
if self.0.position() == 0 && buf.is_empty() {
mem::swap(buf, self.0.get_mut());
Ok(buf.len())
} else {
self.0.read_to_end(buf)
}
}
}
impl<'a, R: 'a + Read> ImageDecoder<'a> for JpegDecoder<R> {
type Reader = JpegReader<R>;
fn dimensions(&self) -> (u32, u32) {
(u32::from(self.metadata.width), u32::from(self.metadata.height))
}
fn color_type(&self) -> ColorType {
ColorType::from_jpeg(self.metadata.pixel_format)
}
fn into_reader(mut self) -> ImageResult<Self::Reader> {
let mut data = self.decoder.decode().map_err(ImageError::from_jpeg)?;
data = match self.decoder.info().unwrap().pixel_format {
jpeg::PixelFormat::CMYK32 => cmyk_to_rgb(&data),
_ => data,
};
Ok(JpegReader(Cursor::new(data), PhantomData))
}
fn read_image(mut self, buf: &mut [u8]) -> ImageResult<()> {
assert_eq!(u64::try_from(buf.len()), Ok(self.total_bytes()));
let mut data = self.decoder.decode().map_err(ImageError::from_jpeg)?;
data = match self.decoder.info().unwrap().pixel_format {
jpeg::PixelFormat::CMYK32 => cmyk_to_rgb(&data),
_ => data,
};
buf.copy_from_slice(&data);
Ok(())
}
}
fn cmyk_to_rgb(input: &[u8]) -> Vec<u8> {
let size = input.len() - input.len() / 4;
let mut output = Vec::with_capacity(size);
for pixel in input.chunks(4) {
let c = f32::from(pixel[0]) / 255.0;
let m = f32::from(pixel[1]) / 255.0;
let y = f32::from(pixel[2]) / 255.0;
let k = f32::from(pixel[3]) / 255.0;
let c = c * (1.0 - k) + k;
let m = m * (1.0 - k) + k;
let y = y * (1.0 - k) + k;
let r = (1.0 - c) * 255.0;
let g = (1.0 - m) * 255.0;
let b = (1.0 - y) * 255.0;
output.push(r as u8);
output.push(g as u8);
output.push(b as u8);
}
output
}
impl ColorType {
fn from_jpeg(pixel_format: jpeg::PixelFormat) -> ColorType {
use jpeg::PixelFormat::*;
match pixel_format {
L8 => ColorType::L8,
RGB24 => ColorType::Rgb8,
CMYK32 => panic!(),
}
}
}
impl ImageError {
fn from_jpeg(err: jpeg::Error) -> ImageError {
use jpeg::Error::*;
match err {
Format(desc) => ImageError::FormatError(desc),
Unsupported(desc) => ImageError::UnsupportedError(format!("{:?}", desc)),
Io(err) => ImageError::IoError(err),
Internal(err) => ImageError::FormatError(err.to_string()),
}
}
}