qoicodec/tests/codec.rs

use qoicodec::DecodeError;
use qoicodec::Decoder;
use qoicodec::PixelRGBA;

use std::io::BufWriter;
use std::path::Path;
use std::{fs::File, io::Read};

#[derive(Debug)]
enum TestError {
    SetupFailure, // an error during test initialization (missing file, no write permission for output)
    CodecFailure(DecodeError),
}

impl From<DecodeError> for TestError {
    fn from(err: DecodeError) -> Self {
        Self::CodecFailure(err)
    }
}

#[test]
/// There are test images provided by the QOI spec author: https://qoiformat.org/qoi_test_images.zip
/// This function looks for them in `./qoi_test_images/` and turns them all
/// into PNGs. Manual inspection is required to evaluate the test result.
fn decode_qoi_samples() -> Result<(), TestError> {
    let file = File::open("qoi_test_images/dice.qoi").map_err(|_io_err| TestError::SetupFailure)?;

    // TODO: feed the Result<> forward, don't let a panic path be given to an unaware caller.
    let mut bytes = file.bytes()
        .map(|maybe_bytes|
        {
            match maybe_bytes {
                Ok(byte) => byte,
                Err(oops) => panic!("Oops, the file failed to load: {}", oops)
            }
        });
    let decoder = Decoder::try_new(bytes)?;
    
    let test_out_path = Path::new("test_output.png");
    let file = File::create(test_out_path).unwrap();
    let ref mut w = BufWriter::new(file);
    
    let mut encoder = png::Encoder::new(w, decoder.width, decoder.height);
    encoder.set_color(match decoder.channels {
        3 => png::ColorType::Rgb,
        4 => png::ColorType::Rgba,
        _ => panic!("Bad colorspace in qoicodec::Decoder!")
    });
    encoder.set_depth(png::BitDepth::Eight);
    encoder.set_source_gamma(png::ScaledFloat::from_scaled(45455));
    encoder.set_source_gamma(png::ScaledFloat::new(1.0 / 2.2));
    let source_chromaticities = png::SourceChromaticities::new(
        (0.31270, 0.32900),
        (0.64000, 0.33000),
        (0.30000, 0.60000),
        (0.15000, 0.06000),
    );
    encoder.set_source_chromaticities(source_chromaticities);
    let mut writer = encoder.write_header().unwrap();

    let data: Vec<u8> = PixelIterExpander::try_new(decoder).unwrap().collect();
    let result = writer.write_image_data(&data);
    if let Err(res) = result {
        panic!("{}", res);
    }
    return Ok(())
}

struct PixelIterExpander <I: Iterator<Item = qoicodec::PixelRGBA>> {
    wrapped_iterator: I,
    current_pixel: qoicodec::PixelRGBA,
    color_element_idx: u8,
}

impl <I: std::iter::Iterator<Item = PixelRGBA>> PixelIterExpander <I> {
    fn try_new(mut pixels: I) -> Option<Self> {
        let px = pixels.next()?;

        Some(Self {
            wrapped_iterator: pixels,
            current_pixel: px,
            color_element_idx: 0,
        })
    }
}

impl <I: Iterator<Item=PixelRGBA>> Iterator for PixelIterExpander<I> {
    type Item = u8;

    fn next(&mut self) -> Option<Self::Item> {
        // at index 4, reset counter and get next pixel
        if self.color_element_idx == 4 {
            self.color_element_idx = 0;
            self.current_pixel = self.wrapped_iterator.next()?;
        }

        // increment pixel value, match over index and return that byte
        self.color_element_idx += 1;
        match self.color_element_idx {
            1 => Some(self.current_pixel.r),
            2 => Some(self.current_pixel.g),
            3 => Some(self.current_pixel.b),
            4 => Some(self.current_pixel.a),
            _ => None
        }
    }
}