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Clean up some color quantization code (#2730)

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frozolotl 2023-11-21 10:24:39 +01:00 committed by GitHub
parent c1bc529986
commit 8e5b7fe5c1
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1 changed files with 4 additions and 26 deletions
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30
crates/typst-pdf/src/color.rs
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@ -431,26 +431,7 @@ impl ColorSpaceExt for ColorSpace {
fn convert<U: QuantizedColor>(self, color: Color) -> [U; 3] {
let range = self.range();
let [x, y, z, _] = color.to_space(self).to_vec4();
// We need to add 0.4 to y and z for Oklab
// This is because DeviceN color spaces in PDF can **only** be in
// the range 0..1 and some readers enforce that.
// The oklab color space is in the range -0.4..0.4
// Also map the angle range of HSV/HSL to 0..1 instead of 0..360
let [x, y, z] = match self {
Self::Oklab => {
let [l, c, h, _] = color.to_oklch().to_vec4();
// Clamp on Oklch's chroma, not Oklab's a\* and b\* as to not distort hue.
let c = c.clamp(0.0, 0.5);
// Convert cylindrical coordinates back to rectangular ones.
let a = c * h.to_radians().cos();
let b = c * h.to_radians().sin();
[l, a + 0.5, b + 0.5]
}
Self::Hsv | Self::Hsl => [x / 360.0, y, z],
_ => [x, y, z],
};
let [x, y, z, _] = self.encode(color);
[
U::quantize(x, [range[0], range[1]]),
@ -466,12 +447,9 @@ pub(super) trait QuantizedColor {
}
impl QuantizedColor for u16 {
fn quantize(color: f32, range: [f32; 2]) -> Self {
let value = (color - range[0]) / (range[1] - range[0]);
(value.max(0.0).min(1.0) * Self::MAX as f32)
.round()
.max(0.0)
.min(Self::MAX as f32) as Self
fn quantize(color: f32, [min, max]: [f32; 2]) -> Self {
let value = (color - min) / (max - min);
(value * Self::MAX as f32).round().clamp(0.0, Self::MAX as f32) as Self
}
}