PDF presets: Press Quality converts to the document's profile, keeping its numbers (#2950)

Press Quality left Output at No conversion, so in a CMYK document RGB images went to the press as
DeviceRGB. It now converts to the destination with the numbers kept, the destination blank (the
document's profile): RGB comes out CMYK in a CMYK document, CMYK values stay exactly, RGB
documents are unchanged, and no profiles are included, as a printer's published [Press Quality]
settings list.

crates/pdf/src/presets.rs

@@ -5,8 +5,8 @@
 use serde::{Deserialize, Serialize};
 
 use crate::{
-    BleedSettings, Compatibility, CompressionSettings, Downsample, ImageCodec, ImageCompression, JpegQuality, MonoCodec, MonoCompression,
-    PdfSettings, Standard,
+    BleedSettings, ColorConversion, Compatibility, CompressionSettings, Downsample, ImageCodec, ImageCompression, JpegQuality, MonoCodec,
+    MonoCompression, OutputSettings, PdfSettings, Standard,
 };
 
 /// The built-in preset every PDF export starts from.
@@ -62,10 +62,18 @@ pub fn builtin_presets() -> Vec<PdfPreset> {
             PdfSettings { preserve_editing: true, ..Default::default() },
         ),
         preset("High Quality Print", "For desktop printers and proofs: images stay at print resolution.", print(ImageCodec::Auto, false)),
+        // Converted to the document's profile, its own numbers kept: in a CMYK document RGB colours
+        // and images come out CMYK, as a press needs (#2950). A printer's published settings for
+        // the [Press Quality] preset list the same Output: Convert to Destination (Preserve
+        // Numbers), Document CMYK, no profiles included
+        // (https://postmediasolutions.com/hubfs/Website/Client%20Resources/PostmediaPrintPDFSpecSheet.pdf).
         preset(
             "Press Quality",
-            "For commercial printing: high-resolution images compressed losslessly, the document's bleed.",
-            print(ImageCodec::Zip, true),
+            "For commercial printing: high-resolution images compressed losslessly, the document's bleed, colours converted to the document's profile with its own numbers kept (RGB comes out CMYK in a CMYK document).",
+            PdfSettings {
+                output: OutputSettings { conversion: ColorConversion::PreserveNumbers, ..Default::default() },
+                ..print(ImageCodec::Zip, true)
+            },
         ),
         preset(
             "Smallest File Size",

crates/pdf/src/tests_cmykimages.rs

@@ -429,3 +429,21 @@ fn a_cmyk_image_masked_by_a_grey_image_of_its_grid_writes_it_as_its_smask() {
     assert_eq!(smasks, [None]);
     assert!(String::from_utf8_lossy(&bytes).contains("/S/Luminosity"), "a luminosity soft mask");
 }
+
+/// #2950: Press Quality converts to the document's profile with its numbers kept, so in a CMYK
+/// document an RGB image comes out CMYK, as the press needs; with no conversion (the default
+/// preset) it stays RGB, as before.
+#[test]
+fn press_quality_writes_an_rgb_image_in_a_cmyk_document_as_cmyk() {
+    let rgb = image::RgbImage::from_fn(4, 4, |x, y| image::Rgb([(x * 60) as u8, (y * 60) as u8, 128]));
+    let blob = ImageBlob { mime: "image/png".into(), bytes: Arc::new(png(rgb)), proxy: None };
+    let d = image_doc(blob, 4, 4);
+    let press = builtin_presets().into_iter().find(|p| p.name == "Press Quality").unwrap().settings;
+    assert_eq!(press.output.conversion, ColorConversion::PreserveNumbers);
+    let options = PdfOptions { settings: press, created: Some(1_700_000_000), ..Default::default() };
+    let w = written(&export_with_report(&d, &options).unwrap().bytes);
+    assert_eq!(w.len(), 1, "{w:?}");
+    assert_eq!((w[0].space.as_str(), w[0].icc_n), ("DeviceCMYK", None), "Press Quality");
+    let w = written(&export_with_report(&d, &opts(json!({}))).unwrap().bytes);
+    assert_eq!(w[0].space, "DeviceRGB", "no conversion");
+}