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[Merged by Bors] - Add conversions from Color to u32 #4088

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[Merged by Bors] - Add conversions from Color to u32 #4088

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0c0125c
add Color::as_rgba_u32 and Color::as_linear_rgba_u32
Azorlogh Mar 3, 2022
d8b1508
fix comment typo
Azorlogh Mar 4, 2022
a64ec66
improve comment
Azorlogh Mar 7, 2022
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88 changes: 87 additions & 1 deletion crates/bevy_render/src/color/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -414,7 +414,7 @@ impl Color {
}
}

/// Converts a `Color` to a `[f32; 4]` from linear RBG colorspace
/// Converts a `Color` to a `[f32; 4]` from linear RGB colorspace
#[inline]
pub fn as_linear_rgba_f32(self: Color) -> [f32; 4] {
match self {
Expand Down Expand Up @@ -487,6 +487,92 @@ impl Color {
} => [hue, saturation, lightness, alpha],
}
}

/// Converts a `Color` to a `u32` from sRGB colorspace.
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Would it makes sense to describe how the colour is converted to u32 (each channel as a u8, order as alpha-blue-green-red) or is it standard enough to do it that way?

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I think it should be described. Perhaps both endianness (it wasn’t obvious to me a while ago that GPUs were generally little endian) and order.

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Should I change the comment to the following?
Converts Color to a u32 from sRGB colorspace, mapping the RGBA channels in this order to a little-endian byte array (meaning A will be the most significant byte and R the least significant).

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Sounds good to me.

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Suggested change
/// Converts a `Color` to a `u32` from sRGB colorspace.
/// Converts Color to a u32 from sRGB colorspace
///
/// Maps the RGBA channels in RGBA order to a little-endian byte array (GPUs are little-endian).
/// A will be the most significant byte and R the least significant.

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A will be the most significant byte

that took me two reads to understand, with "will" being also a noun 😄

pub fn as_rgba_u32(self: Color) -> u32 {
match self {
Color::Rgba {
red,
green,
blue,
alpha,
} => u32::from_le_bytes([
(red * 255.0) as u8,
(green * 255.0) as u8,
(blue * 255.0) as u8,
(alpha * 255.0) as u8,
]),
Color::RgbaLinear {
red,
green,
blue,
alpha,
} => u32::from_le_bytes([
(red.linear_to_nonlinear_srgb() * 255.0) as u8,
(green.linear_to_nonlinear_srgb() * 255.0) as u8,
(blue.linear_to_nonlinear_srgb() * 255.0) as u8,
(alpha * 255.0) as u8,
]),
Color::Hsla {
hue,
saturation,
lightness,
alpha,
} => {
let [red, green, blue] =
HslRepresentation::hsl_to_nonlinear_srgb(hue, saturation, lightness);
u32::from_le_bytes([
(red * 255.0) as u8,
(green * 255.0) as u8,
(blue * 255.0) as u8,
(alpha * 255.0) as u8,
])
}
}
}

/// Converts a `Color` to a `u32` from linear RGB colorspace
pub fn as_linear_rgba_u32(self: Color) -> u32 {
match self {
Color::Rgba {
red,
green,
blue,
alpha,
} => u32::from_le_bytes([
(red.nonlinear_to_linear_srgb() * 255.0) as u8,
(green.nonlinear_to_linear_srgb() * 255.0) as u8,
(blue.nonlinear_to_linear_srgb() * 255.0) as u8,
(alpha * 255.0) as u8,
]),
Color::RgbaLinear {
red,
green,
blue,
alpha,
} => u32::from_le_bytes([
(red * 255.0) as u8,
(green * 255.0) as u8,
(blue * 255.0) as u8,
(alpha * 255.0) as u8,
]),
Color::Hsla {
hue,
saturation,
lightness,
alpha,
} => {
let [red, green, blue] =
HslRepresentation::hsl_to_nonlinear_srgb(hue, saturation, lightness);
u32::from_le_bytes([
(red.nonlinear_to_linear_srgb() * 255.0) as u8,
(green.nonlinear_to_linear_srgb() * 255.0) as u8,
(blue.nonlinear_to_linear_srgb() * 255.0) as u8,
(alpha * 255.0) as u8,
])
}
}
}
}

impl Default for Color {
Expand Down