picto 0.4.4

Image handling library.
Documentation 
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//            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
//                    Version 2, December 2004
//
// Copyleft (ↄ) meh. <meh@schizofreni.co> | http://meh.schizofreni.co
//
// Everyone is permitted to copy and distribute verbatim or modified
// copies of this license document, and changing it is allowed as long
// as the name is changed.
//
//            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
//   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
//
//  0. You just DO WHAT THE FUCK YOU WANT TO.

use std::io::Read;

use jpeg_decoder as jpeg;

use crate::{
	buffer::{cast, Buffer},
	color,
	error::{self, Error},
	pixel,
};

pub struct Decoder<R: Read> {
	inner: jpeg::Decoder<R>,
	metadata: Option<jpeg::ImageInfo>,
}

impl<R: Read> Decoder<R> {
	#[inline]
	pub fn new(input: R) -> Self {
		Decoder {
			inner: jpeg::Decoder::new(input),
			metadata: None,
		}
	}

	#[inline]
	pub fn metadata(&mut self) -> error::Result<jpeg::ImageInfo> {
		if self.metadata.is_none() {
			self.inner.read_info()?;
			self.metadata = Some(self.inner.info().unwrap());
		}

		Ok(self.metadata.unwrap())
	}
}

impl<P, C, R> super::Decoder<P, C> for Decoder<R>
where
	P: pixel::Write<C>,
	P: From<color::Rgb> + From<color::Luma>,
	C: pixel::Channel,
	R: Read,
{
	fn frame(&mut self) -> error::Result<Buffer<P, C, Vec<C>>> {
		#[inline]
		fn convert(buffer: &mut Vec<u8>) {
			let length = buffer.len();
			let mut cmyk = 0;
			let mut rgb = 0;

			while cmyk < length {
				let c = buffer[cmyk] as f32 / 255.0;
				let m = buffer[cmyk + 1] as f32 / 255.0;
				let y = buffer[cmyk + 2] as f32 / 255.0;
				let k = buffer[cmyk + 3] as f32 / 255.0;

				// CMYK -> CMY
				let c = c * (1.0 - k) + k;
				let m = m * (1.0 - k) + k;
				let y = y * (1.0 - k) + k;

				// CMY -> RGB
				let r = (1.0 - c) * 255.0;
				let g = (1.0 - m) * 255.0;
				let b = (1.0 - y) * 255.0;

				buffer[rgb] = r as u8;
				buffer[rgb + 1] = g as u8;
				buffer[rgb + 2] = b as u8;

				cmyk += 4;
				rgb += 3;
			}

			buffer.resize((length / 4) * 3, 0);
			buffer.shrink_to_fit();
		}

		let mut buffer = self.inner.decode()?;

		macro_rules! buffer {
			($ch:ty, $ty:path) => {{
				Ok(cast::Into::<P, C>::into(Buffer::<$ty, $ch, _>::from_raw(
					self.metadata()?.width as u32,
					self.metadata()?.height as u32,
					buffer,
				)
				.map_err(|_| Error::Format("wrong dimensions".into()))?))
			}};
		}

		match self.metadata()?.pixel_format {
			jpeg::PixelFormat::L8 => buffer!(u8, color::Luma),

			jpeg::PixelFormat::RGB24 => buffer!(u8, color::Rgb),

			jpeg::PixelFormat::CMYK32 => {
				convert(&mut buffer);
				buffer!(u8, color::Rgb)
			}
		}
	}
}