From 494308a038d6c4c31b4c05d444f67fa9ac06978c Mon Sep 17 00:00:00 2001 From: itsF4LCON <107556180+itsF4LCON@users.noreply.github.com> Date: Thu, 15 Oct 2026 09:28:55 +0200 Subject: [PATCH] Image Size: Indexed Color resamples with Nearest Neighbor only (#6019) An Indexed Color document holds only its colour table's colours, and a save quantises to them. Interpolating methods showed blended colours on screen that the saved file then lost. image.imageSize now resamples an Indexed document with Nearest Neighbor whatever method it is given, and the dialog offers only Automatic and Nearest Neighbor for one. --- crates/engine/src/image_cmds.rs | 27 ++++++++++++++++++++++ crates/ui-egui/src/sizing.rs | 40 ++++++++++++++++++++++++++++++++- 2 files changed, 66 insertions(+), 1 deletion(-) diff --git a/crates/engine/src/image_cmds.rs b/crates/engine/src/image_cmds.rs index 3e870aa686..5f37a2eaa8 100644 --- a/crates/engine/src/image_cmds.rs +++ b/crates/engine/src/image_cmds.rs @@ -171,6 +171,12 @@ fn image_size(s: &mut Session, p: &Value) -> Result { let d = s.active().ok_or(EngineError::NoDocument)?; let (ow, oh) = (d.doc.size.width, d.doc.size.height); let resample = parse_resample(p.get("resample").and_then(Value::as_str).unwrap_or("bicubic")); + // An Indexed Color document holds only its colour table's colours, and a save quantises to + // them: interpolation showed blends that the saved file didn't have (#6019). + let resample = match resample { + Method::Filter(_) | Method::Automatic if d.doc.mode == ColorMode::Indexed => Method::Filter(Resample::Nearest), + m => m, + }; let mut pw = p.get("width").and_then(Value::as_f64); let mut ph = p.get("height").and_then(Value::as_f64); // `percent` scales both sides (what a Photoshop action records as "200%"); an explicit side wins. @@ -943,6 +949,27 @@ mod tests { /// #1544: 64 x 48 to 300000 x 300000 (90 billion pixels) started allocating resampled bands /// without a budget. It is refused before any allocation and the document is untouched; a /// change of resolution only, and an ordinary resize, still work. + #[test] + fn image_size_resamples_indexed_color_with_nearest_neighbor() { + let mut s = Session::new(); + s.execute("file.new", json!({"width": 2, "height": 1})).unwrap(); + s.execute("edit.fill", json!({"color": "#ff0000"})).unwrap(); + s.execute("select.rect", json!({"x": 1, "y": 0, "width": 1, "height": 1})).unwrap(); + s.execute("edit.fill", json!({"color": "#0000ff"})).unwrap(); + s.execute("select.deselect", json!({})).unwrap(); + s.execute("image.mode.indexedColor", json!({})).unwrap(); + for resample in ["bicubic", "automatic", "bilinear", "lanczos", "preserveDetails"] { + s.execute("image.imageSize", json!({"width": 8, "resample": resample})).unwrap(); + let st = s.active().unwrap(); + let surf = st.doc.layers[0].surface().unwrap(); + for x in 0..8 { + let px = surf.pixel(x, 0); + assert!(px[..3] == [1.0, 0.0, 0.0] || px[..3] == [0.0, 0.0, 1.0], "{resample}: no blended colour at x {x}: {px:?}"); + } + s.execute("history.undo", json!({})).unwrap(); + } + } + #[test] fn image_size_refuses_a_raster_past_the_budget() { let mut s = Session::new(); diff --git a/crates/ui-egui/src/sizing.rs b/crates/ui-egui/src/sizing.rs index 3c48e041f4..c3ec7a199b 100644 --- a/crates/ui-egui/src/sizing.rs +++ b/crates/ui-egui/src/sizing.rs @@ -70,7 +70,7 @@ pub fn reset(f: &mut Map) { pub fn open(app: &mut PhotocraftApp, command: &str) -> Option { let unit = pref_unit(app.session.prefs().units_and_rulers.rulers); - let resample = pref_resample(app.session.prefs().general.image_interpolation); + let mut resample = pref_resample(app.session.prefs().general.image_interpolation); let pt_per_in = app.session.prefs().units_and_rulers.point_size.per_inch(); let d = &app.session.active()?.doc; let (w, h, res) = (d.size.width as f64, d.size.height as f64, d.resolution_dpi as f64); @@ -88,6 +88,12 @@ pub fn open(app: &mut PhotocraftApp, command: &str) -> Option { f.insert("width".into(), json!(w)); f.insert("height".into(), json!(h)); if command == "image.imageSize" { + // Indexed Color resamples with Nearest Neighbor only, as the command does (#6019). + let indexed = d.mode == photocraft_color::ColorMode::Indexed; + if indexed && resample != "automatic" { + resample = "nearest"; + } + f.insert("__indexed".into(), json!(indexed)); f.insert("__constrain".into(), json!(true)); f.insert("resolution".into(), json!(res)); f.insert("resample".into(), json!(resample)); @@ -321,6 +327,10 @@ fn image_size(ui: &mut egui::Ui, f: &mut Map) { ("bilinear".to_string(), tl!("Bilinear")), ("lanczos".to_string(), tl!("Lanczos (sharp)")), ]; + // Indexed Color: every other method blends colours the colour table doesn't have, + // which the command doesn't use and a save quantises away (#6019). + let indexed = f.get("__indexed").and_then(Value::as_bool) == Some(true); + let opts: Vec<_> = opts.into_iter().filter(|(k, _)| !indexed || k == "automatic" || k == "nearest").collect(); if crate::widgets::dropdown(ui, "is-resample", &mut cur, &opts, 200.0) { f.insert("resample".into(), json!(cur)); } @@ -517,6 +527,34 @@ mod tests { /// The dialog starts on Preferences › General › Image Interpolation: Bicubic Automatic opens /// as Automatic and the others as themselves (Bicubic Sharper used to open as Lanczos). + #[test] + fn indexed_color_resamples_with_nearest_neighbor_only() { + let mut app = PhotocraftApp::new(photocraft_engine::Session::new(), crate::Services::default()); + app.session.execute("file.new", json!({"width": 200, "height": 100})).unwrap(); + app.session.execute("image.mode.indexedColor", json!({})).unwrap(); + for (pref, method) in [("bicubic", "nearest"), ("bicubicAutomatic", "automatic"), ("nearestNeighbor", "nearest")] { + app.session.execute("prefs.set", json!({"path": "general.imageInterpolation", "value": pref})).unwrap(); + let id = open(&mut app, "image.imageSize").unwrap(); + let f = &app.ui.dialog_mut(id).unwrap().fields; + assert_eq!(f.get("resample"), Some(&json!(method)), "{pref}"); + assert_eq!(f.get("__indexed"), Some(&json!(true))); + app.ui.close_dialog(id); + } + // The open list offers only Automatic and Nearest Neighbor. + use egui_kittest::{Harness, kittest::Queryable}; + let mut h = Harness::builder().with_size(egui::vec2(1400.0, 900.0)).build_ui_state(|ui, app| crate::dialogs::show(app, ui.ctx()), app); + PhotocraftApp::setup_context(&h.ctx, crate::theme::ThemeKind::ALL[0]); + open(h.state_mut(), "image.imageSize").unwrap(); + h.run_steps(3); + let combo = h.query_all_by_role(egui::accesskit::Role::ComboBox).find(|n| n.value().as_deref() == Some("Nearest Neighbor (hard edges)")); + combo.expect("the Resample list shows Nearest Neighbor").click(); + h.run_steps(3); + assert!(h.query_by_label_contains("Automatic").is_some(), "Automatic is offered"); + for gone in ["Bicubic", "Bilinear", "Lanczos", "Preserve Details"] { + assert!(h.query_by_label_contains(gone).is_none(), "{gone} is not offered for Indexed Color"); + } + } + #[test] fn resample_follows_the_interpolation_preference() { let mut app = PhotocraftApp::new(photocraft_engine::Session::new(), crate::Services::default());