Panic when call blur with sigma == 0.0

[Aloxaf]

This happens in when call image::imageops::blur with sigma == 0.0, however imageproc::filter::gaussian_blur_f32 works well (edit: seee image-rs/imageproc#331 )

Expected

Nothing happen

Actual behaviour

It panicked

Reproduction steps

use image::RgbaImage;
use image::imageops::blur;
use imageproc::filter::gaussian_blur_f32;

fn main() {
    let image = RgbaImage::new(50, 50);
    dbg!();
    let _ = gaussian_blur_f32(&image, 0.0);
    dbg!();
    let _ = blur(&image, 0.0);
}

Backtrace

thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', src/libcore/option.rs:347:21
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.29/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:47
   3: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:36
   4: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:198
   5: std::panicking::default_hook
             at src/libstd/panicking.rs:212
   6: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:475
   7: std::panicking::continue_panic_fmt
             at src/libstd/panicking.rs:382
   8: rust_begin_unwind
             at src/libstd/panicking.rs:309
   9: core::panicking::panic_fmt
             at src/libcore/panicking.rs:85
  10: core::panicking::panic
             at src/libcore/panicking.rs:49
  11: core::option::Option<T>::unwrap
             at /rustc/b25ee644971a168287ee166edbd11642dbcfeab8/src/libcore/macros.rs:12
  12: image::imageops::sample::vertical_sample
             at /home/aloxaf/.cargo/registry/src/github.com-1ecc6299db9ec823/image-0.21.2/./src/imageops/sample.rs:284
  13: image::imageops::sample::blur
             at /home/aloxaf/.cargo/registry/src/github.com-1ecc6299db9ec823/image-0.21.2/./src/imageops/sample.rs:710
  14: tmp2::main
             at src/main.rs:10
  15: std::rt::lang_start::{{closure}}
             at /rustc/b25ee644971a168287ee166edbd11642dbcfeab8/src/libstd/rt.rs:64
  16: std::rt::lang_start_internal::{{closure}}
             at src/libstd/rt.rs:49
  17: std::panicking::try::do_call
             at src/libstd/panicking.rs:294
  18: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:82
  19: std::panicking::try
             at src/libstd/panicking.rs:273
  20: std::panic::catch_unwind
             at src/libstd/panic.rs:388
  21: std::rt::lang_start_internal
             at src/libstd/rt.rs:48
  22: std::rt::lang_start
             at /rustc/b25ee644971a168287ee166edbd11642dbcfeab8/src/libstd/rt.rs:64
  23: main
  24: __libc_start_main
  25: _start
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

[Aloxaf]

I thinks this should be changed to something like let sigma = if sigma < 0.0 { /* return the original image */ } else { sigma };

[HeroicKatora]

This may be caused by having an empty kernel support, hence the sum being 0.0 resulting in division by 0 in floating points cause the NumCast::from argument to be NaN which can not be cast to an integral type and instead yields a None value that is then unwrapped.

The proposed fix, with a slight change, should be good enough then:

let sigma = if sigma <= 0.0 { /* return the original image */ } else { sigma };

[Aloxaf]

@HeroicKatora Thank you. I forgot to change the operator.

However, image-rs/imageproc#331 was fixed by explicitly rejecting sigama <= 0.0. Is there a need to maintain consistency between these two functions? (But this seems to lead a breaking change on this crate

[HeroicKatora]

Right. That's something to consider for the future. It also relates to #977 in that removing it from this crate would certainly make it consistent ;) But it would be very prompt to do it because of a bug, the issue should involve better planning.