Thread 'main' panicked at 'called `Option::unwrap()` on a `None` value'

[Josh]

Describe the bug
The attached image seems to crash while attempting to decode with the following error (referencing this line)

thread 'main' panicked at 'called `Option::unwrap()` on a `None` value'

To Reproduce

// "raw" is an &[u8] of the raw file.
let png_pong::Step { raster, .. } = png_pong::Decoder::new(raw)
	.unwrap()
	.into_steps()
	.last();

Screenshots

Desktop (please complete the following information):

• OS: Debian Buster
• Rust: stable-x86_64-unknown-linux-gnu (default) / rustc 1.52.1 (9bc8c42bb 2021-05-09)

[Jeryn Aldaron Lau]

@joshstoik1 Thanks! I'll look into fixing this.

[Jeryn Aldaron Lau]

@joshstoik1 Should be fixed in 0.8.1 (just released on crates.io)

[Josh]

Thanks @AldaronLau!

Version 0.8.1 fixes the panic for me, but when I try the following, the PngRaster's palette and trailing vec are both empty:

// Loading from a slice, works A-OK now.
let png_pong::Step { raster, .. } = png_pong::Decoder::new(raw)
	.map_err(|_| Error::Source)?
	.into_steps()
	.last()
	.ok_or(tError::Source)
	.map_err(|_| Error::Source)?
	.map_err(|_| Error::Source)?;

// Trying to extract the inner raster bits...
let raster = match raster {
	PngRaster::Palette(x, y, z) => {
		println!("{:?} {:?}", y.len(), z.len()); // 0 0
	},
	...
}

If I use into_chunks() instead of into_steps(), there is a Palette object in there with the correct number of colors for this image. So basically the data just doesn't make it into the step's PngRaster::Palette(_, here, _).

png_pong::Decoder::new(raw)
	.map_err(|_| Error::Source)?
	.into_chunks()
	.for_each(|x| {
		match x {
			Ok(Chunk::Palette(Palette { palette })) => {
				println!("{:?}", palette.len()); // 221
			},
			_ => {}
		}
	});

If I remap the grey indexes from steps to the above palette, all's right with the world. 😉

(If you'd like me to open a new issue, please let me know. Thanks!)

[Jeryn Aldaron Lau]

@joshstoik1 Thanks for the extra information! I just tried your code, and with your provided PNG everything works fine (the palette makes it into PngRaster). The alpha vec should be empty since there's no alpha channel in the image. Full test code:

fn main() -> png_pong::decode::Result<()> {
    let raw = std::fs::read("test.png").unwrap();
    let raw = raw.as_slice();

    let png_pong::Step { raster, .. } = png_pong::Decoder::new(raw)?
	    .into_steps()
	    .last()
	    .unwrap()
	    .unwrap();

    let raster = match raster {
	    png_pong::PngRaster::Palette(x, y, z) => {
		    println!("{:?} {:?}", y.len(), z.len()); // 221 0
	    },
	    _ => {},
    };
    
    Ok(())
}

I'm not sure what you're doing different, any ideas?

[Jeryn Aldaron Lau]

@joshstoik1 Just figured out why that's happenning, I'll release 0.8.2 in a moment.

[Jeryn Aldaron Lau]

@joshstoik1 Just released 0.8.2, should be fixed now!