honour the /Lab colour space /WhitePoint (#1203) (#1237)

* fix: recognize paragraph drafts as unsaved work (Issue #811)

* fix(color): honour the /Lab colour space /WhitePoint (#1203)

The old path fed every Lab value to the bundled ICC transform as if the
space's white point were D50, so a /Lab space with any other /WhitePoint
(e.g. D65 [0.9505 1 1.089]) rendered off by several levels per channel
and a D65 blue came out 45 levels too red.

Map L*a*b* to XYZ in the space's own white coordinates (ISO 32000-2
§8.6.5.4), Bradford-adapt it to D65 and convert to sRGB directly, as
Poppler does. Missing or degenerate white points fall back to a flat
white and hostile components are clamped without panicking.

Add a render regression that checks the five reported flat patches of
the D65 white-point fixture against their CIE sRGB values.

* Lab: map normalised Indexed palette components onto L*/Range; drop unused LAB.icc

An /Indexed palette over Lab passes its entries as byte/255 (manual_scale),
which the new Lab conversion read as raw L*a*b* and drew near black. Map
them onto L* 0..100 and the a*/b* /Range, with a regression test. Record the
patch as hayro-interpret (25) in vendor/README.md, and remove LAB.icc (no
longer referenced) with its ATTRIBUTION, NOTICE and assets README entries.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Main gates: rustfmt tests/viewer.rs; a type alias for the refresh-steps array (clippy type_complexity)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Brandon Thomas <echelon@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/render/src/raster.rs

@@ -1905,6 +1905,98 @@ mod tests {
         assert!(remainder.is_empty());
         assert!(pixels.iter().all(|pixel| *pixel == [0, 0, 255, 255]));
     }
+    /// #1203: a /Lab colour space must honour its own /WhitePoint. The old path
+    /// fed every Lab value to the ICC transform as if the white point were D50,
+    /// shifting non-D50 pages several levels per channel (for example a D65
+    /// blue came out 45 levels too red). Conversion and expected values follow
+    /// ISO 32000-2 §8.6.5.4 with the space's own /WhitePoint [0.9505 1 1.089].
+    #[test]
+    fn lab_honours_the_space_white_point() {
+        use super::*;
+        let render = |l: f32, a: f32, b: f32| -> [u8; 4] {
+            let content = format!("/L cs {l} {a} {b} sc 0 0 200 200 re f");
+            let bytes = format!(
+                "%PDF-1.7\n1 0 obj << /Type /Catalog /Pages 2 0 R >> endobj\n\
+                 2 0 obj << /Type /Pages /Kids [3 0 R] /Count 1 >> endobj\n\
+                 3 0 obj << /Type /Page /Parent 2 0 R /MediaBox [0 0 200 200] /Resources << /ColorSpace << /L [/Lab << /WhitePoint [0.9505 1 1.089] /Range [-100 100 -100 100] >>] >> >> /Contents 4 0 R >> endobj\n\
+                 4 0 obj << /Length {} >> stream\n{content}\nendstream endobj\n\
+                 trailer << /Root 1 0 R >>\n%%EOF",
+                content.len()
+            )
+            .into_bytes();
+            let page = PageRenderer::new(Arc::new(bytes), RenderConfig::default()).render(RenderRequest {
+                page: 0,
+                kind: RequestKind::Pixels,
+                tile: None,
+                scale: 1.0,
+                tag: 0,
+                preview: false,
+            });
+            assert!(page.error.is_none(), "Lab ({l} {a} {b}): {:?}", page.error);
+            assert_eq!((page.width, page.height), (200, 200));
+            page.rgba[(100 * page.width as usize + 100) * 4..][..4].try_into().unwrap()
+        };
+
+        for (l, a, b, expected) in [
+            (40.0, 20.0, -60.0, [19, 90, 194, 255]),
+            (70.0, -50.0, 30.0, [77, 193, 114, 255]),
+            (60.0, 0.0, -40.0, [87, 148, 215, 255]),
+            (50.0, 60.0, 40.0, [217, 61, 55, 255]),
+            (30.0, 40.0, 20.0, [130, 37, 42, 255]),
+        ] {
+            let got = render(l, a, b);
+            for (channel, (got, want)) in got.iter().zip(expected).enumerate() {
+                assert!((*got).abs_diff(want) <= 2, "Lab ({l} {a} {b}) channel {channel}: got {got:?}, expected {expected:?}");
+            }
+        }
+    }
+    /// #1203: an `/Indexed` palette over Lab looks its entries up as
+    /// `byte / 255`, which must map onto L* 0..100 and the a*/b* /Range. They
+    /// were read as raw L*a*b* (L* below 1), so such palettes drew near black.
+    #[test]
+    fn indexed_palettes_over_lab_keep_their_colours() {
+        use super::*;
+        let lab = "[/Lab << /WhitePoint [0.9505 1 1.089] /Range [-100 100 -100 100] >>]";
+        let render = |content: &str| -> [u8; 4] {
+            let bytes = format!(
+                "%PDF-1.7\n1 0 obj << /Type /Catalog /Pages 2 0 R >> endobj\n\
+                 2 0 obj << /Type /Pages /Kids [3 0 R] /Count 1 >> endobj\n\
+                 3 0 obj << /Type /Page /Parent 2 0 R /MediaBox [0 0 200 200] /Resources << /ColorSpace << /L {lab} /I [/Indexed {lab} 1 <000000 80CCB2>] >> >> /Contents 4 0 R >> endobj\n\
+                 4 0 obj << /Length {} >> stream\n{content}\nendstream endobj\n\
+                 trailer << /Root 1 0 R >>\n%%EOF",
+                content.len()
+            )
+            .into_bytes();
+            let page = PageRenderer::new(Arc::new(bytes), RenderConfig::default()).render(RenderRequest {
+                page: 0,
+                kind: RequestKind::Pixels,
+                tile: None,
+                scale: 1.0,
+                tag: 0,
+                preview: false,
+            });
+            assert!(page.error.is_none(), "{content}: {:?}", page.error);
+            assert_eq!((page.width, page.height), (200, 200));
+            let start = (100 * page.width as usize + 100) * 4;
+            let mut pixel = [0; 4];
+            pixel.copy_from_slice(page.rgba.get(start..start + 4).expect("centre pixel"));
+            pixel
+        };
+
+        // Palette entry 1 is <80 CC B2>: L* = 128/255·100, a* = -100 + 204/255·200,
+        // b* = -100 + 178/255·200, about Lab (50.2 60 39.6): a warm red.
+        let indexed = render("/I cs 1 sc 0 0 200 200 re f");
+        let direct = render(&format!(
+            "/L cs {} {} {} sc 0 0 200 200 re f",
+            128.0 / 255.0 * 100.0,
+            -100.0 + 204.0 / 255.0 * 200.0,
+            -100.0 + 178.0 / 255.0 * 200.0
+        ));
+        for (channel, (got, want)) in indexed.iter().zip(direct).enumerate() {
+            assert!(got.abs_diff(want) <= 1, "channel {channel}: indexed {indexed:?}, direct {direct:?}");
+        }
+        assert!(indexed[0] > 180, "the palette red must not render near black: {indexed:?}");
+    }
     #[test]
     fn watchdog_skips_a_stuck_page_and_keeps_rendering() {
         use super::*;