From 3275ec85d831180be81820de06cca29a97a757f5 Mon Sep 17 00:00:00 2001
From: Bruce Mitchener <bruce.mitchener@gmail.com>
Date: Wed, 4 Dec 2024 22:04:33 +0700
Subject: [PATCH] Be explicit about CPAL color space (#763)

The OpenType specification defines that this data is sRGB and Skrifa
follows along. Be clear about it here though as even if other things
change with color, this should be sure to be interpreting that data
correctly.
---
 vello/src/scene.rs | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/vello/src/scene.rs b/vello/src/scene.rs
index 555ca5f4..aba8ab68 100644
--- a/vello/src/scene.rs
+++ b/vello/src/scene.rs
@@ -6,7 +6,7 @@ mod bitmap;
 use std::sync::Arc;
 
 use peniko::{
-    color::{palette, DynamicColor, Srgb},
+    color::{palette, AlphaColor, DynamicColor, Srgb},
     kurbo::{Affine, BezPath, Point, Rect, Shape, Stroke, Vec2},
     BlendMode, Blob, Brush, BrushRef, Color, ColorStop, ColorStops, ColorStopsSource, Compose,
     Extend, Fill, Font, Gradient, Image, Mix, StyleRef,
@@ -979,7 +979,9 @@ fn conv_brush(
     }
 }
 
-fn color_index(cpal: &'_ Cpal<'_>, palette_index: u16) -> Option<Color> {
+// The OpenType color palette is defined to be using the sRGB color space.
+// <https://learn.microsoft.com/en-us/typography/opentype/spec/cpal#palette-entries-and-color-records>
+fn color_index(cpal: &'_ Cpal<'_>, palette_index: u16) -> Option<AlphaColor<Srgb>> {
     // The "application determined" foreground color should be used
     // This will be handled by the caller
     if palette_index == 0xFFFF {
@@ -988,7 +990,7 @@ fn color_index(cpal: &'_ Cpal<'_>, palette_index: u16) -> Option<Color> {
     let actual_colors = cpal.color_records_array().unwrap().unwrap();
     // TODO: Error reporting in the `None` case
     let color = actual_colors.get(usize::from(palette_index))?;
-    Some(Color::from_rgba8(
+    Some(AlphaColor::<Srgb>::from_rgba8(
         color.red,
         color.green,
         color.blue,