From aa57554176f2fb996fd017251a81887f4d38d9fa Mon Sep 17 00:00:00 2001
From: Laurenz Stampfl <47084093+LaurenzV@users.noreply.github.com>
Date: Sun, 15 Dec 2024 23:36:09 +0100
Subject: [PATCH] Add proper support for CMYK and luma

---
 crates/typst-pdf/src/krilla.rs | 15 ++++++++++-----
 crates/typst-pdf/src/paint.rs  | 31 +++++++++++++++++++++++++++----
 2 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/crates/typst-pdf/src/krilla.rs b/crates/typst-pdf/src/krilla.rs
index 14efb135b..a04973d24 100644
--- a/crates/typst-pdf/src/krilla.rs
+++ b/crates/typst-pdf/src/krilla.rs
@@ -296,7 +296,7 @@ pub fn pdf(
             }
             KrillaError::ValidationError(ve) => {
                 // We can only produce 1 error, so just take the first one.
-                let prefix = "validated export failed:";
+                let prefix = format!("validated export for {} failed:", options.validator.as_str());
                 match &ve[0] {
                     ValidationError::TooLongString => {
                         bail!(Span::detached(), "{prefix} a PDF string longer than 32767 characters";
@@ -323,6 +323,7 @@ pub fn pdf(
                         bail!(Span::detached(), "{prefix} the PDF has too many indirect objects";
                             hint: "reduce the size of your document");
                     }
+                    // Can only occur if we have 27+ nested clip paths
                     ValidationError::TooHighQNestingLevel => {
                         bail!(Span::detached(), "{prefix} the PDF has too high q nesting";
                             hint: "reduce the number of nested containers");
@@ -337,11 +338,11 @@ pub fn pdf(
                     }
                     ValidationError::ContainsNotDefGlyph => {
                         bail!(Span::detached(), "{prefix} the PDF contains the .notdef glyph";
-                            hint: "ensure all text can be displayed using a font");
+                            hint: "ensure all text can be displayed using an available font");
                     }
                     ValidationError::InvalidCodepointMapping(_, _) => {
                         bail!(Span::detached(), "{prefix} the PDF contains the disallowed codepoints";
-                            hint: "make sure you don't use the Unicode characters 0x0, 0xFEFF or 0xFFFE");
+                            hint: "make sure to not use the Unicode characters 0x0, 0xFEFF or 0xFFFE");
                     }
                     ValidationError::UnicodePrivateArea(_, _) => {
                         bail!(Span::detached(), "{prefix} the PDF contains characters from the Unicode private area";
@@ -349,11 +350,15 @@ pub fn pdf(
                     }
                     ValidationError::Transparency => {
                         bail!(Span::detached(), "{prefix} document contains transparency";
-                            hint: "remove any transparency in your document and your SVGs";
+                            hint: "remove any transparency from your document (e.g. fills with opacity)";
+                            hint: "you might have to convert certain SVGs into a bitmap image if they contain transparency";
                             hint: "export using a different standard that supports transparency"
                         );
                     }
-                    // The below errors cannot occur yet, only once Typst supports PDF/A and PDF/UA.
+
+                    // The below errors cannot occur yet, only once Typst supports full PDF/A
+                    // and PDF/UA.
+                    // But let's still add a message just to be on the safe side.
                     ValidationError::MissingAnnotationAltText => {
                         bail!(Span::detached(), "{prefix} missing annotation alt text";
                             hint: "please report this as a bug");
diff --git a/crates/typst-pdf/src/paint.rs b/crates/typst-pdf/src/paint.rs
index 1f549175b..6321f1027 100644
--- a/crates/typst-pdf/src/paint.rs
+++ b/crates/typst-pdf/src/paint.rs
@@ -57,7 +57,7 @@ fn dash(dash: &DashPattern<Abs, Abs>) -> krilla::path::StrokeDash {
     }
 }
 
-fn convert_color(color: &Color) -> (krilla::color::rgb::Color, u8) {
+fn convert_to_rgb_color(color: &Color) -> (krilla::color::rgb::Color, u8) {
     let components = color.to_space(ColorSpace::Srgb).to_vec4_u8();
     (
         krilla::color::rgb::Color::new(components[0], components[1], components[2])
@@ -75,8 +75,31 @@ fn paint(
 ) -> SourceResult<(krilla::paint::Paint, u8)> {
     match paint {
         Paint::Solid(c) => {
-            let (c, alpha) = convert_color(c);
-            Ok((c.into(), alpha))
+            let (p, alpha) = match c.space() {
+                ColorSpace::D65Gray => {
+                    let components = c.to_vec4_u8();
+                    (
+                        krilla::color::luma::Color::new(components[0])
+                            .into(),
+                        components[3],
+                    )
+                }
+                ColorSpace::Cmyk => {
+                    let components = c.to_vec4_u8();
+                    (
+                        krilla::color::cmyk::Color::new(components[0], components[1], components[2], components[3])
+                            .into(),
+                        // Typst doesn't support alpha on CMYK colors.
+                        255,
+                    )
+                }
+                _ => {
+                    let (c, a) = convert_to_rgb_color(c);
+                    (c.into(), a)
+                }
+            };
+
+            Ok((p, alpha))
         }
         Paint::Gradient(g) => Ok(convert_gradient(g, on_text, transforms)),
         Paint::Pattern(p) => convert_pattern(gc, p, on_text, surface, transforms),
@@ -154,7 +177,7 @@ fn convert_gradient(
     let mut stops: Vec<krilla::paint::Stop<krilla::color::rgb::Color>> = vec![];
 
     let mut add_single = |color: &Color, offset: Ratio| {
-        let (color, opacity) = convert_color(color);
+        let (color, opacity) = convert_to_rgb_color(color);
         let opacity = NormalizedF32::new((opacity as f32) / 255.0).unwrap();
         let offset = NormalizedF32::new(offset.get() as f32).unwrap();
         let stop = krilla::paint::Stop { offset, color, opacity };