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https://github.com/storytold/vectorcraft.git
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bflatastic
934d83405c
A CMYK page with transparency is drawn through an alpha soft mask that covers the page (a non-isolated group). Its cover was black: opaque as alpha, but nothing shows in a reader that takes the mask's luminosity. A white cover is the same mask either way.
88 lines
3.5 KiB
Rust
88 lines
3.5 KiB
Rust
//! Blending in CMYK documents: transparency groups blend in DeviceCMYK.
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use std::sync::Arc;
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use vectorcraft_color::{BlendMode, Color, Paint};
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use vectorcraft_doc::{Appearance, ColorMode, Document, Node, NodeId, OpacityMask};
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use vectorcraft_geom::{Rect, shapes};
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use crate::*;
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fn rect(r: Rect, c: Color) -> Node {
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Node::path(NodeId(0), shapes::rectangle(r), Appearance::basic(Paint::solid(c), Paint::None, 0.0))
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}
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fn add(d: &mut Document, mut n: Node) {
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n.id = d.alloc_id();
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let l = d.layers[0].id;
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d.insert(Some(l), usize::MAX, n).unwrap();
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}
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/// Magenta with cyan multiplied over it: in a group when `grouped`, else at the top of the page.
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fn doc(mode: ColorMode, grouped: bool) -> Document {
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let mut d = Document::new_with_mode(100.0, 100.0, mode);
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add(&mut d, rect(Rect::new(0.0, 0.0, 100.0, 100.0), Color::cmyk(0.0, 1.0, 0.0, 0.0)));
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let mut top = rect(Rect::new(20.0, 20.0, 80.0, 80.0), Color::cmyk(1.0, 0.0, 0.0, 0.0));
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top.blend = BlendMode::Multiply;
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if grouped {
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top.id = d.alloc_id();
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let mut g = Node::group(NodeId(0), vec![Arc::new(top)]);
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g.opacity = 0.5;
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add(&mut d, g);
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} else {
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add(&mut d, top);
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}
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d
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}
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/// The file's text with spaces removed (content streams uncompressed), after checking it reads.
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fn text(d: &Document) -> String {
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let bytes = export(d, &PdfOptions::uncompressed()).unwrap();
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import(&bytes).expect("the rewritten file still reads");
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String::from_utf8_lossy(&bytes).replace(' ', "")
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}
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#[test]
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fn groups_of_cmyk_documents_blend_in_device_cmyk() {
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for grouped in [true, false] {
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let t = text(&doc(ColorMode::Cmyk, grouped));
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// Top-level blending gets a group of its own, so it blends in CMYK too.
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assert!(t.contains("/S/Transparency") && t.contains("/CS/DeviceCMYK"), "grouped {grouped}: {t}");
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assert!(!t.contains("/CS/DeviceRGB"), "grouped {grouped}: {t}");
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assert!(t.contains("/BM/Multiply"));
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}
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// Compressed output gets the same group dictionaries.
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let bytes = export(&doc(ColorMode::Cmyk, true), &PdfOptions::default()).unwrap();
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assert!(String::from_utf8_lossy(&bytes).contains("/CS/DeviceCMYK"));
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}
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#[test]
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fn rgb_documents_and_opaque_cmyk_pages_are_unchanged() {
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let t = text(&doc(ColorMode::Rgb, true));
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assert!(t.contains("/CS/DeviceRGB") && !t.contains("/CS/DeviceCMYK"), "{t}");
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let mut d = doc(ColorMode::Cmyk, false);
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let top = d.layers[0].children().unwrap()[1].id;
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d.node_mut(top).unwrap().blend = BlendMode::Normal;
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assert!(!text(&d).contains("/Transparency"));
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}
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#[test]
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fn soft_mask_groups_keep_screen_luminance() {
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let mut d = Document::new_with_mode(100.0, 100.0, ColorMode::Cmyk);
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let mut n = rect(Rect::new(0.0, 0.0, 100.0, 100.0), Color::cmyk(0.0, 0.0, 0.0, 1.0));
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n.extras_mut().mask = Some(Box::new(OpacityMask::new(rect(Rect::new(0.0, 0.0, 50.0, 100.0), Color::WHITE), true)));
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add(&mut d, n);
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let t = text(&d);
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// The page's group blends in CMYK; the mask's group measures luminance in RGB.
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assert!(t.contains("/CS/DeviceCMYK") && t.contains("/S/Luminosity") && t.contains("/CS/DeviceRGB"), "{t}");
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}
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#[test]
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fn constant_alpha_masks_are_white() {
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// #1286: a black cover hides the whole page in readers that take the mask's luminosity.
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for grouped in [true, false] {
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let t = text(&doc(ColorMode::Cmyk, grouped));
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assert!(t.contains("/S/Alpha") && t.contains("111rg") && !t.contains("000rg"), "grouped {grouped}: {t}");
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}
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}
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