extern crate png;
use self::png::HasParameters;
use std::io::{self, Read, Write};
use image::{ImageError, ImageResult, DecodingResult, ImageDecoder};
use color::ColorType;
enum Either<T, U> {
Left(T),
Right(U)
}
pub struct PNGDecoder<R: Read> {
inner: Option<Either<png::Decoder<R>, png::Reader<R>>>
}
impl<R: Read> PNGDecoder<R> {
pub fn new(r: R) -> PNGDecoder<R> {
PNGDecoder {
inner: Some(Either::Left(png::Decoder::new(r)))
}
}
fn get_reader(&mut self) -> Result<&mut png::Reader<R>, png::DecodingError> {
let inner = self.inner.take().unwrap();
self.inner = Some(match inner {
Either::Left(decoder) => {
let (_, reader) = try!(decoder.read_info());
Either::Right(reader)
},
Either::Right(reader) => Either::Right(reader)
});
match self.inner {
Some(Either::Right(ref mut reader)) => Ok(reader),
_ => unreachable!()
}
}
}
impl<R: Read> ImageDecoder for PNGDecoder<R> {
fn dimensions(&mut self) -> ImageResult<(u32, u32)> {
let reader = try!(self.get_reader());
Ok(reader.info().size())
}
fn colortype(&mut self) -> ImageResult<ColorType> {
let reader = try!(self.get_reader());
Ok(reader.output_color_type().into())
}
fn row_len(&mut self) -> ImageResult<usize> {
let reader = try!(self.get_reader());
let width = reader.info().width;
Ok(reader.output_line_size(width))
}
fn read_scanline(&mut self, buf: &mut [u8]) -> ImageResult<u32> {
match try!(try!(self.get_reader()).next_row()) {
Some(line) => {
::copy_memory(line, &mut buf[..line.len()]);
Ok(line.len() as u32)
},
None => Err(ImageError::ImageEnd)
}
}
fn read_image(&mut self) -> ImageResult<DecodingResult> {
let reader = try!(self.get_reader());
let mut data = vec![0; reader.output_buffer_size()];
try!(reader.next_frame(&mut data));
Ok(DecodingResult::U8(data))
}
}
pub struct PNGEncoder<W: Write> {
w: W
}
impl<W: Write> PNGEncoder<W> {
pub fn new(w: W) -> PNGEncoder<W> {
PNGEncoder {
w: w
}
}
pub fn encode(self, data: &[u8], width: u32, height: u32, color: ColorType) -> io::Result<()> {
let (ct, bits) = color.into();
let mut encoder = png::Encoder::new(self.w, width, height);
encoder.set(ct).set(bits);
let mut writer = try!(encoder.write_header());
writer.write_image_data(data).map_err(|e| e.into())
}
}
impl From<(png::ColorType, png::BitDepth)> for ColorType {
fn from((ct, bits): (png::ColorType, png::BitDepth)) -> ColorType {
use self::png::ColorType::*;
let bits = bits as u8;
match ct {
Grayscale => ColorType::Gray(bits),
RGB => ColorType::RGB(bits),
Indexed => ColorType::Palette(bits),
GrayscaleAlpha => ColorType::GrayA(bits),
RGBA => ColorType::RGBA(bits)
}
}
}
impl From<ColorType> for (png::ColorType, png::BitDepth) {
fn from(ct: ColorType) -> (png::ColorType, png::BitDepth) {
use self::png::ColorType::*;
let (ct, bits) = match ct {
ColorType::Gray(bits) => (Grayscale, bits),
ColorType::RGB(bits) => (RGB, bits),
ColorType::Palette(bits) => (Indexed, bits),
ColorType::GrayA(bits) => (GrayscaleAlpha, bits),
ColorType::RGBA(bits) => (RGBA, bits)
};
(ct, png::BitDepth::from_u8(bits).unwrap())
}
}
impl From<png::DecodingError> for ImageError {
fn from(err: png::DecodingError) -> ImageError {
use self::png::DecodingError::*;
match err {
IoError(err) => ImageError::IoError(err),
Format(desc) => ImageError::FormatError(desc.into_owned()),
InvalidSignature => ImageError::FormatError("invalid signature".into()),
CrcMismatch { .. } => ImageError::FormatError("CRC error".into()),
Other(desc) => ImageError::FormatError(desc.into_owned()),
CorruptFlateStream => ImageError::FormatError("compressed data stream corrupted".into())
}
}
}