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moppeeerandClaude Opus 5.5
dc712baeca
LYH Studio episode 6 builds every gradient from C=0 M=100 Y=0 K=0 to C=100 M=0 Y=0 K=0. InDesign blends a gradient's process stops as inks: halfway is C 50 M 50, a light lilac. DesignCraft converted both ends to RGB and blended there, so the middle came out a darker violet (117, 88, 189 instead of 135, 119, 181), and every Episode 6 gradient looked different. A midpoint between CMYK stops also became an RGB colour, so the PDF shading turned RGB with a conversion warning. - color: `Color::lerp` blends CMYK with CMYK (or grey), and grey with grey, in ink space; anything with RGB still blends in RGB. - `Gradient::display_stops`: the expanded stops plus samples through each span that isn't RGB at both ends, for renderers that interpolate in RGB; the screen renderer uses it. - pdf: a midpoint's expanded stop now keeps the stops' space; the colour-space test expects no conversion for CMYK or grey midpoints. Co-Authored-By: Claude Opus 5.5 <[email protected]>
37 lines
1.8 KiB
Rust
37 lines
1.8 KiB
Rust
//! A gradient between process colours shows the inks' blend, as InDesign shows it.
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use designcraft_color::swatch::Swatch;
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use designcraft_color::{Color, Gradient, GradientKind, GradientStop, SwatchValue};
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use designcraft_compose::Cache;
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use designcraft_doc::build::NewDocument;
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use designcraft_doc::{Document, Fill, Item, ItemId, Shape, SpreadRef, Stroke};
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use designcraft_geom::{Affine, Rect, shapes};
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use designcraft_render::{Placed, RenderOptions, Renderer};
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#[test]
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fn a_cmyk_gradient_is_c50_m50_halfway() {
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let mut d = Document::new(&NewDocument { width: 100.0, height: 20.0, facing_pages: false, ..Default::default() });
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let stop = |offset: f32, color: Color| GradientStop { offset, color, opacity: 1.0, midpoint: 0.5 };
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let gradient =
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Gradient { kind: GradientKind::Linear, stops: vec![stop(0.0, Color::cmyk(0.0, 1.0, 0.0, 0.0)), stop(1.0, Color::cmyk(1.0, 0.0, 0.0, 0.0))] };
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d.swatches.push(Swatch { name: "Magenta to Cyan".into(), value: SwatchValue::Gradient { gradient }, locked: false, named: true, hidden: false });
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let id = ItemId(d.alloc());
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let mut item = Item::new(id, d.default_layer(), Shape::Rectangle, shapes::rectangle(Rect::new(0.0, 0.0, 100.0, 20.0)));
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item.fill = Fill::swatch("Magenta to Cyan");
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item.stroke = Stroke::default();
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d.insert_item(SpreadRef::Doc(0), item, None).unwrap();
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let img = Renderer::new().render(
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&d,
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&Cache::new(),
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&[Placed { spread: SpreadRef::Doc(0), xf: Affine::IDENTITY }],
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100,
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20,
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Affine::IDENTITY,
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&RenderOptions { paper: false, background: Some([255; 4]), ..Default::default() },
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);
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let want = Color::cmyk(0.5, 0.5, 0.0, 0.0).to_rgba8(1.0);
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let got = img.pixel(50, 10);
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for ch in 0..3 {
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assert!(got[ch].abs_diff(want[ch]) <= 4, "halfway {got:?}, the inks' blend is {want:?}");
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}
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}
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