From 453e0e4fc1ef669bc702dce20111e83b341b4041 Mon Sep 17 00:00:00 2001
From: ickshonpe <david.curthoys@googlemail.com>
Date: Mon, 22 Jul 2024 19:22:26 +0100
Subject: [PATCH] Prevent division by zero in HWBA to HSVA conversions (#14256)

# Problem

Division by zero in `crates/bevy_color/src/hsva.rs` when `blackness` is
`1`:

```rust
impl From<Hwba> for Hsva {
    fn from(
        Hwba {
            hue,
            whiteness,
            blackness,
            alpha,
        }: Hwba,
    ) -> Self {
        // Based on https://en.wikipedia.org/wiki/HWB_color_model#Conversion
        let value = 1. - blackness;
        let saturation = 1. - (whiteness / value);

        Hsva::new(hue, saturation, value, alpha)
    }
}
```

## Solution
With `Hsva` colors if the `value` component is set to `0.` the output
will be pure black regardless of the values of the `hue` or `saturation`
components.

So if `value` is `0`, we don't need to calculate a `saturation` value
and can just set it to `0`:

```rust
impl From<Hwba> for Hsva {
    fn from(
        Hwba {
            hue,
            whiteness,
            blackness,
            alpha,
        }: Hwba,
    ) -> Self {
        // Based on https://en.wikipedia.org/wiki/HWB_color_model#Conversion
        let value = 1. - blackness;
        let saturation = if value != 0. {
            1. - (whiteness / value)
        } else {
            0.
        };

        Hsva::new(hue, saturation, value, alpha)
    }
}

```

---------

Co-authored-by: Gino Valente <49806985+MrGVSV@users.noreply.github.com>
---
 crates/bevy_color/src/hsva.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/crates/bevy_color/src/hsva.rs b/crates/bevy_color/src/hsva.rs
index 3e6fefce05..e708ccf67e 100644
--- a/crates/bevy_color/src/hsva.rs
+++ b/crates/bevy_color/src/hsva.rs
@@ -157,7 +157,11 @@ impl From<Hwba> for Hsva {
     ) -> Self {
         // Based on https://en.wikipedia.org/wiki/HWB_color_model#Conversion
         let value = 1. - blackness;
-        let saturation = 1. - (whiteness / value);
+        let saturation = if value != 0. {
+            1. - (whiteness / value)
+        } else {
+            0.
+        };
 
         Hsva::new(hue, saturation, value, alpha)
     }